Thesis Report - Highrise Constrxn.pdf

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PROJECTREPORT

BARRIERS TO HIGH RISE CONSTRUCTION

Guide: Mr. Muralidhar

BY

R.PRASANNA VENKATESH (213067)PRATAP.B.PATIL (213068)M. VENKATESH (213107)



BARRIERS TO HIGH RIS E CONSTRUCTION

NICM AR PROJECT REPORT 2

CONTENTS

1. INTRODUCTION..............................................................................................................................4

1.1. DEFINING HIGH RIS E BUILDINGS ........................................................................................5

1.2. HISTORICAL DEVELOPMENT .................................................. ..............................................6

1.3. WHY HIGH RIS E IN INDIA? ........................................... .......... ................................................9

1.3.1. URBANIZATION AT THE MACRO LEVEL ...................................... ...................................10

1.3.2. URBANIZATION PATT ERN ....................................................................................................10

2. ARCH ITECTURAL ASPECTS AND URBAN DEVELOPMENT TODAY ............................17

3. FINANCING MODELS ......................................................... .........................................................19

3.2. COST MODELS ............................................................... ................................................ ...........22

3.2.1. LEASING......................................................................................................................................22

3.2.2. BOT ...............................................................................................................................................23

3.2.3. DEVELOPER...............................................................................................................................23

4. BARRIERS .................................................... ....................................... ............................................24

4.1. INFRASTRUCTURAL AS PECTS ................................ ....................................... ........... ..........24

4.2. ECO NOMIC AS PECTS..............................................................................................................25

4.3. SOCIAL AND ECO LOGICAL ASPECTS ............................................... ................................26

4.4. TECHNOLOGY OF HIGH-RIS E CONSTRUCTION............................................................46

4.5 CULTURAL RES PONSE ............................. ..................................................................................83

4.6 ENVIRONMENTAL ASPECTS ....................................................................................................84

5 CONCLUS ION.......................................................... .....................................................................108





AIM: -

To study about the high rise structures and different barriers for the construction of highrise building in India.

OBJECTIVE:-To overcome the barriers and to find a suitable solution for the construction of high rise

building w ith reference to Indian context.

What is a barrier?Barrier in dictionary means a fencing that creates an obstacle. In this thesis the term

barrier means the difficulties the construction industry faces during the actual executionas well as the planning of the high rise buildings.

1. To study the barriers and Impact of the following aspects on High rise construction

1.1 Planning and Scheduling

1.2 Technical or Technology

1.3 Economical

1.4 Cost

1.5 Social

1.6 Environmental and





1. INTRODUCTION

From the beginning in the middle ofthe last century and right up to the present day,high-rise buildings have always been a dominantlandmark in the townscape, visible from far andwide, like the towers of Antiquity and the MiddleAges. At the same time, this sky-scrapingconstruction method has always been an idealmeans of displaying power and influence in thecommunity. In the light of this goal, reasonableeconomic considerations often recede into the

background during the erec tion and subsequentuse of these high-rise buildings. A prestige objectsfor the builder, these edifices not only have aneffect on their immediate neighbours, but alsoinfluence many areas of urban life in verydifferent ways. These aspects will also be taken upin this thesis.

In the ear ly years, the builders’ urge to r ise to d izzying heights was limited

by unsolved technical problems. In recent years, however, a real competition hasdeveloped among the builders of skyscrapers to be world champion at least for a fewmonths before being outdone by a rival with an even higher building. Even seeminglyUtop ian projects now stand a good chance of becoming reality.

This rapid development has only become possible because the technicalconditions and methods used in constructing high-rise buildings have improveddecisively and in some cases changed fundamentally in the last few years. Up until theend of the last century, high-rise buildings were still made of solid brick masonry, whichultimately required foundation walls up to 1.8 m thick. When steel frames adapted fromsteel bridge construction were introduced, with their increased strength and lower weight,

builders and architects were able to soar to greater heights. With this steel skeleton, thenet weight of the structure was considerably lower than that of a solid masonry building;it thus not only cut the costs of construction, but also gave wings to the architects’imagination. By the turn of the century, they were designing buildings that also lookedlight and delicate as even at that time the skeleton structure permitted a large proportionof windows on the outer facade. Since then, the construction of high-rise buildings hascontinued to change with the requirements imposed by air-conditioning and particularlyoffice communications.





The high-rise office buildings of the nineties have little in common withtheir predecessors. Instead of compact walls and ceilings, we now have a high-tech

structure made up of largely prefabricated elements which are welded and bondedtogether on site. The building comprises a skeleton of steel or reinforced concrete whichis rounded off by suspended ceilings and false floors creating the space required forinstallations. The originally load-bearing outer wall has been replaced by a prefabricatedfacade. However, this complex method of construction promotes the spread of fire andfumes, and therefore, in conjunction with the considerable concentration of valuesinvolved, represents an extremely sensitive risk both during construction and throughoutthe service life of the building. The major fires which broke out in a number of high-riseoffice buildings shortly before their completion in the early nineties show how correct theappraisal of the fire risk in high-rise buildings is the losses incurred through these firesare several times higher than the amounts of indemnity known to date.

This is consequently one of the main reasons why high rise buildingsconstitute a new dimension of risk for the insurance industry, one which has made itnecessary to draw up new concepts for underwriting, loss assessment and PMLdetermination throughout every phase of construction and subsequent use. We are fullyaware of the fact that many of the aspects considered with regard to the construction, useand insurance of high-rise buildings naturally apply in the case of lower buildings too.

Nevertheless , we do not wish to limit ourselves to aspects which only applyspecifically to high rise buildings. After a brief overview, we will therefore consider in

detail all the risks and problems associated with high-rise buildings and the techniquesthat are applied in order to illuminate possible solutions from the point of view of bothconstruction technology. Moreover, the more broadly based general information availablewill make it easier not only to assess the risk of high-rise building projects but also toarrive at a price for such projects.

1.1. Defining High Rise Buildings

The definition of a high-rise building differsfrom one country to the next. For our purposes, we will

proceed on the basis of a minimum height of 30 m and willrestrict ourselves to buildings used for residential or office

purposes. Despite the various critical voices raised, theconstruction of high-rise buildings has by no means reachedits zenith.

A high-rise is a tall building or structure.Massachusetts General Laws define a high-rise as beinghigher than 70 feet (21 m). Buildings between 75 feet and





491 feet (23 m to 150 m) high are considered high-rises. Buildings taller than 492 feet(150 m) are classified as skyscrapers. The average height of a level is around 13 feet (4

m) high, thus a 79 foot (24 m) tall building would comprise 6 floors. Most buildingengineers, inspectors, architects and similar professions define a high-rise as a buildingthat is at least 75 feet (23 m).

Davis Langdon (2002) states that it is not possible to define high rise usingabsolute measures. They believe that “tall buildings are therefore best understood inrelative terms as buildings whose planning, design, construction and occupation isinfluenced by height in ways that are not normally associated with more typical, localdevelopments”.

High-rise buildings became possible with the invention of the elevator (lift)and cheaper, more abundant building materials. Normally, the high rise structuresfunction’s as high-rise apartment building or high-rise offices.

For the sake of this study, the terms tall building and high-rise shall be usedfor structures with approximately eight or more stories while towers are tall buildingswith a slender shape.

1.2. Historical development

What could be a more appropriate point to begin our consideration of high-

rise buildings than with the Tower of Babel and then to trace their historical developmentover the centuries. However, a distinction must be made between “high buildings” and“high-rise buildings”: “high buildings” have only a few floors and not uncommonly onlyone, albeit very high floor. They are crowned by a high roof and turrets (in the mannertypical of medieval and Gothic cathedrals). “High-rise buildings”, on the other hand,have many, usually identical floors of normal height one above the other.

Seen in this light, high-rise buildings have their origins in the towers of SanGimignano rather than in the Tower of Babel or ecclesiastical structures. The first high-rise office building according to this definition was built in Chicago in 1885: the HomeInsurance Building. It still stands on the corner of La Salle and Adams Street, a witnessof its times. It has twelve floors – there were originally ten, but two were subsequentlyadded – and was built in roughly eighteen months. The architect W. L. B. Jenney used anuncommon new method for the construction of his building: the weight of the walls was

borne by a framework of cast-iron columns and rolled I-sections which were boltedtogether via L-bars and the entire “skeleton” embedded in the masonry.

The early Equitable Life Building in New York, which was completed in1872, also contributed towards the development of high-rise bu ildings, for it was the firsttall building to have an elevator. Although it only had s ix floors, the edge of the roof wasno less than 130 feet (roughly 38 m) above the road surface. Due to its elevator, the upper





floors were in greater demand than the lower floors. Following completion of the“Equitable” building, it was the done thing to reside on one of the “top” floors.

Burnham and Roof’s Monadnock building, which was completed in Chicagoin 1891, must also be mentioned as one of the last witnesses of a whole generation ofsolid masonry high-rise buildings. Sixteen floors of robust brick masonry rise skywardsin stern, c lear lines: an astonishing s ight to eyes accustomed to the frills and fancies ofthe late 19th century. Standing on an oblong base measuring 59 m _ 20 m, the building isreminiscent of a thin slice and not only recalls the industrial brick buildings of the late19th century, but also anticipates the formal simplification of the later 1920s.

The buildings rose higher and higher with the spread of pioneeringconstruction methods – such as the steel skeleton or reliable deep foundation methods –as well as the invention and development of the elevator. The highly spectacular skylinesof North American cities, particularly Chicago and New York, originated in the earlyyears of the 20th century. Glancing over Manhattan’s stony profile, the silhouettesdotting the firs t 12 km of the 22-km-long is land bear vociferous testimony to th isdynamic development:

The World Trade Center, currently the tallest building in New York, 417 m high, The legendary Empire State Building, built in 1931, 381 m, The United Nations building erected in 1953, 215

m, The Chrysler Building dated 1930, 320 m,

The former Pan Am Building completed in 1963,246 m,

The Rockefeller Center (1931–1940), a complexof 19 buildings,

The Citicorp Center built in 1978, 279 m, and The AT&T Building opened in 1984, a

pioneering building by the post-modern architectPhilip Johnson, with an overall height of 197 m.

It is only recently that attention has alsoturned to interesting high-rise buildings outside NorthAmerica: Norman Foster’s Hong Kong and ShanghaiBank, Ieoh Ming Pei’s Bank of China in Hong Kongand the twin tops of the Petronas Towers in KualaLumpur, currently the tallest building in the world at452 m. High-rise buildings in Germany are a moderndevelopment and are concentrated particularly inFrankfurt am Main: today, Frankfurt is the only German





city with a skyline dominated by skyscrapers. One of the tallest buildings in the city is theMesseturm built in 1991 with a height of 259 m, which is not much more than half the

height of the Sears Tower in Chicago, currently the tallest office and business tower in North America with a total height of 443 m. It was the rapid grow th in population thatoriginally promoted the construction of high-rise buildings.

New York once again provides a striking example: land became scarce wellover a hundred years ago as more and more European immigrants streamed into the city.From roughly half a million in 1850, the city’s population grew to 1.4 million by 1899.More and more skyscrapers rose higher and higher on the solid ground in Manhattan, as

buildings could only be erected with great difficulty on the boggy land to the right andleft of the Hudson River and East River. In this way, New York demonstrated what wasmeant by “urban densification” despite the considerable doubts originally voiced byexperts in conjunction with this development.

The first area development code to come into force in New York was the so-called “zoning law” of 1916, according to which the height of a building must not exceedtwo and- a-half times the width of the road running alongside the building. The buildingmass was further limited by the requirement that the floor space index must not exceedtwelve times the area of the site. Among other things, the zoning law stipulated that onlythe first twelve floors of a building were allowed to occupy the full area of the site andthat all subsequent floors must then recede in zoned terraces – a requirement of majoraesthetic significance, for this terraced form still dominates the silhouette of American

skyscrapers today.All doubts as to the profitability of high-rise buildings were set aside withcompletion of the Empire State Building, the Chrysler Building and other skyscrapers inthe 1930s, for they would never have been built if they could not have turned a profit.Although rentals proceeded slowly at first when the Empire State Building wascompleted in the heart of the recession in the 1930s and it was therefore known as the“Empty State Building” for many years, it subsequently generated satisfactory revenuesonce all the premises had been let. Cities in Europe and Asia grew horizontally and it wasonly when production and services acquired greater economic significance throughout theworld and the price of land rose higher and higher in economic centers after the SecondWorld War that they also began to grow vertically.

Modern Hong Kong is a striking case in point: it encompasses an area of1,037 km2 (Victoria, Kowloon and the New Territories), of which only one-quarter has

been developed, but with maximum density and impressive efficiency. Almost all thenew buildings, office towers and particularly residential towers in the New Territorieshave more than thirty floors.





1.3. Why High Rise in India?

In current milieu of increasing urbanization more than half of world's population is living in cities and towns. Nearly twenty eight per cent of India's population(285 million) live in urban areas as per 2001 census. The percentage decadal growth of

population in rural and urban areas during the decade is 17.9 and 31.2 percentrespectively. It is important to note that the contribution of urban sector to GDP iscurrently expected to be in the range of 50-60 percent. Increased urbanization seen todayis a result of this overall growth.

Construction activity is one of the largest activities driving the economy thathas a significant impact on the environment. As per the Confederation of IndianIndustries, the construction sector contributes to 10% of India’s GDP and is growing atthe rate of 9.2% as against the world average of 5.5%.

The high-rise building is also seen as a wealth-generating mechanismworking in an urban economy. High-rise buildings are constructed largely because theycan create a lot of real estate out of a fairly small piece of land. Because of theavailability of global technology and the growing demand for real estate, skyscrapers areseen as the most fitting solution to any city that is spatially challenged and can`tcomfortably house its inhabitants. And hence, maybe it is rightly said that ‘When youcompare the population in our cities with the amount of land we have, the only way to

provide better living condit ions is by building higher’.It is often argued that the process of economic liberalization and associated

structural reform would accelerate rural–urban (RU) migration and boost the pace ofurbanization. Linking of India with global economy would lead to massive inflow offoreign capital as also rise in indigenous investment resulting in an increase inemployment opportunities within or around the existing urban centres. The critics ofglobalization, however, argue that employment generation in the formal urban economymight not be high due to the capital intensive nature of industrialization under the new

policy regime1. A low rate of infrastruc tural investment in the public sector in theattempt to control budgetary deficits would slow down both agricultural as well as agro-industrial growth, resulting in high unemployment and exodus from rural areas. Thiswould lead to rapid growth in urban population leading to the unregulated expansion ofthe urban informal sector. Recent data from Population Census, however, question the

proposition of accelerated urban growth.





1.3.1. URBANIZATION AT THE MACRO LEVEL

The annual exponential growth rate of urban population during 1950s was3.5 per cent. This was the highest the country had seen until that time and led to theemergence of theories of ‘over urbanization’. Subsequently, this high growth rate has

been attributed to independence and part it ion of the country as also non-rigorousidentification of towns and cities in the 1951 Census. Formalization of the criteria foridentifying urban centres in the 1961 Census resulted in a dramatic decline in urbangrowth figures in the following decade. The 1970s, however, following the samemethodology of urban population enumeration, saw a very high urban growth of 3.8 percent, fuelling speculation that India w as on the verge of an urban explosion. Speculationsnotwithstanding, the growth rate came down to 3.1 per cent in the 1980s. It has gonedown further to 2.7 per cent in the 1990s, which is the lowest in the post-independence

period. As a consequence, the percentage of population in urban areas has gone upsluggishly from 17.3 in 1951 to 23.3 in 1981 and then to 27.78 in 2001. But, in terms of

population size, India’s urban population is vast. Moreover, population in large cities hasgrown rapidly and this has led to serious infrastructural deficiencies in urban India.

1.3.2. URBANIZATION PATTERN

An important feature of urbanization in India is dualism— urban growth atmacro level is decelerating but in class I cities it is growing. An analysis of thedistribution of urban population across size categories reveals that the process ofurbanization in India has been large city oriented . This is manifested in a h igh percentageof urban population being concentrated in class I cities, which has gone up systematically





over the decades in the last century. The massive increase in the percentage share ofurban population in class I cities from 26.0 in 1901 to 68.7 in 2001 has often been

attributed to faster growth of large cities, without taking into consideration the increase inthe number of these cities.Undoubtedly, the faster demographic growth is an important factor

responsible for making the urban structure top-heavy. One can note that the class I citieshave experienced a distinctly higher growth rate than lower order towns except those inclass VI. Indeed, the latter do not fall in line with the general pattern of urban growth inother size categories as they are governed by factors exogenous to the regional economy.In the context of demographic dominance of urban scene by class I cities, it is importantto note that there were only 24 classes I cities in 1901 that have gone up to 393 in 2001.While a number of lower order towns have graduated to class I category, the process ofrural settlements acquiring urban characteristics has been weak.

The pattern of growth has remained similar over time although there is ageneral deceleration in urban growth in all size categories in the past two decades. Class Icities have maintained an edge over class II, III, IV and class V towns in terms of thegrow th rate (of common towns). The gap, however, seems to have w idened during 1991– 01. Class I cities in the country experienc ing higher population growth as compared toother categories (except VI) is due to both aerial expansion as well as in-migration. Alarge number of satellite towns have emerged in the vicinity of these cities.





Many of these are becoming a part of the city agglomeration over time. Thereare also outgrowths that have been treated as parts of the agglomeration by the Census.Further, there has been expansion in the municipal boundaries of the class I cities,resulting in higher urban growth figures. The growth pattern of metro cities—citieshaving population of a million or more—corroborate further the thesis of concentrated

urban development. The demographic growth in metro cities has been higher than that ofcommon towns or even the class I cities in recent decades (Figure 2.5). The growthwould have been even higher but for the location of large industrial units outside themunicipal limits, thanks to the pressures exerted by the environment lobby. This isfacilitated by easy availability of land, access to unorganized labour market, besideslesser awareness and less stringent implementation of environmental regulations in therural settlements at the urban periphery. The poor are able to build shelters in these‘degenerated peripheries’ and find jobs in the industries located therein or commute tothe central city for work (Kundu 1989 and Kundu et al. 2002). The entrepreneurs,engineers, executives, etc., associated with modern industries and business, however,reside within the central city and travel to the periphery through rapid transport corridors.

This segmented structure of city growth, variants of which are emerging acrossregions has brought the migrants to the rural peripheries in many large cities. Whiledemographic growth rates in the state capitals and Delhi have been at par with the 3.84

per cent growth in the million plus category of cities during 1981–91, the growth rates ofthe former have declined substantially in the 1990s to 2.79 per cent only. It would beimportant to enquire whether this is because of the strategy of structural adjustment,





expenditure control, fall in the infrastructure investments by the central and stategovernments etc., which could have adversely, affect the growth of the capital cities.

URBANIZATION TREND: AN ANALYSISThe regional variations in the distribution of urban population are significant. A

large proportion is concentrated in six most developed states, namely Maharashtra,

Gujarat, Tamil Nadu, Karnataka, Punjab, and West Bengal, accounting for about half ofthe country’s urban population. By the 2001 Census, they report percentage of urban population much above the national average of 27.78, whereas the less developed statesreport significantly low figures. Indeed, the levels of urbanization are high in the stateswith high per capita income and vice versa (Table 2.2).

The pattern of urban growth across states is significantly different from that of thelevels of urbanization . Since independence until 1991, the developed states that have high

percentage of people in urban areas have shown medium or low growth of urban population. High urban growth has however been registered in relatively underdevelopedstates, viz. Bihar, Uttar Pradesh, Rajasthan, Orissa and Madhya Pradesh, the states thathave low percentages of urban population (Table 2.2) . This implies that the relationship

between urban growth and economic development is genera lly negative. However, someof the developed states like Maharashtra and Haryana are exceptions, as they recordurban growth rates higher than the country average.Urban scenario in the post independence period has, thus, been characterized by dualism.The developed states attracted population in urban areas due to industrialization andinfrastructure investment. Interestingly, the less developed states too, particularly theirrural districts that is, districts having predominantly rural population earlier (for example,Gurgaon) and small and medium towns, experienced rapid urban growth. This can partly





be attributed to government sponsored infrastructural investment in the district and talukaheadquarters, programmes of urban industrial dispersal, and transfer of funds from the

states to local bodies through a need based or what is popularly known as ‘a gap filling’approach. A part of RU migration into smaller towns from their rural hinterland in lessdeveloped states could, however, be explained in terms of push factors, owing to lack ofdiversification in agrarian economy.The 1990s, however, make a significant departure from the earlier decades, since many ofthe developed states like Tamil Nadu, Punjab, Haryana, Maharashtra and Gujarat haveregistered urban growth above the national average (Table 2.2). Karnataka has remainedslightly below the national average and West Bengal is an exception whose growth rate islow due to specific policies followed by the state government. The backward states, onthe other hand, have experienced growth either below that of the country or, at the most,equal to that. Making a comparison over the past two decades, the growth rates fordeveloped states have either gone up or remained the same in the 1990s5. The backwardstates, however, have recorded either a decline or stability in their urban growth.

The urbanization process has, thus, become more concentrated in developedregions with the exclus ion of backward areas in recent years (Figure 2.3). This is alsoreflected in the larger cities recording relatively higher growth when compared to smallertowns, as noted in the preceding section. This could, at least partly, and rather

paradoxically, be attributed to the measures of decentralization whereby theresponsibilities of resource mobilization and launching infrastructural projects have been

given to local bodies, as noted below. Large municipal bodies that have a strongeconomic base, particularly those located in developed s tates; have an advantage that hasclearly been manifested in their high economic and demographic growth.





Eme rging Growth Centres

The real estate action is no longer limited to the large metropolises of India buthas now permeated to the burgeoning smaller tow ns and cities. These emerging centres ofgrowth are lending sparkle to India's booming economy. What is leading thistransformation?

The upswing of the Indian real estate sector has been an outcome of a number of positive micro and macro factors. Consistent and sustaining GDP grow th, expandingservice sector, rising purchasing power and affluence, proactive and changinggovernment policies have all lent momentum to this rapidly growing sector.

Accounting for almost 80% of the total office space absorption, the IndianIT/ITES sector has been the primary demand driver. India's low cost-high quality and

productivity model has given it a leadership posit ion in the outsourc ing arena. In a bid toscale up their operations and to remain globally competitive, the Indian IT/ITEScompanies are exploring the smaller towns and cities. Rising manpower and real estatecosts, plaguing attrition levels and very often risk mitigation have been the key reasonsfor this movement.

Positive economic growth has also translated in rising disposable incomes andgrowing aspiration levels across India. Rising consumerism has created a demand fornew retailing and entertainment avenues.

Realising that consumers across cities have similar needs, albeit the scale may vary, newage retailers are vying to cash in on the first mover advantage and are expanding intohitherto unexplored smaller cities. Advent of organised retailing has also translated intoreal estate growth in these emerging locations.

Growth of the Indian 'Rich' (annual income>USD 4,700) and 'Consuming' (annualincome USD 1,000-4,700) class coupled with falling interest rates and other fiscalincentives on home loans has increased the affordability and the risk appetite of theaverage Indian consumer thereby leading to a substantial rise in demand for housing. Thishas been further fueled by the increase in the size of 25-55 age group of earning

population and the emergence of double income, nuclear families. Over the last decadethe average age of Indian home loan borrower has reduced by 10 years.

Another variable facilitating real estate growth in India is the growingurbanisation. According to United Nations Population Divis ion, the urban population inIndia will continue to grow at a rate of 2.5% per annum for the next two and a halfdecade. As per the Census of India 2001, 41% of the total population of India will beliving in urban areas by 2011. The number of cities with a population of one million ormore is also is expected to double from 35 recorded in 2001 to 70 by 2005. This increasein population will generate incremental demand for housing and other real estatecomponents.





All these factors together with increased liquidity in the real estate sector throughthe international real estate funds and private equity funds will result in radically

transforming the real estate landscape over the next 3-5 years. India's investment scenariois already undergoing a sea change and has been seen to be making roads in rural Indiawith telecom, rural retailing, agricultural supply chain and logistics facilities, micro-credit, etc. All these factors foretell that the real estate growth will soon spread out of theestablished boundaries.

However, to support this growth and to make it more expansive, a lot needs to bedone. Foremost is the thrust on infrastructure. According to a World Bank estimate, Indianeeds to invest an additional 3-4% of its GDP on infrastructure to sustain its currentlevels of growth and to spread the benefits of growth more widely. Some positive stepshave already been taken in this direction. Huge investments in infrastructure to the tuneof $350 billion have been envisaged over the next five years. Connectivity may get a

boost with the completion of ~13,000 kms of roads under the Golden Quadrilatera l, North-South-East-West (NSEW) corridor and with 4-laning of all the major nationalhighways. This will further facilitate the economic development of smaller towns andcities in the country.Major real estate destinations of the country and some other emerging towns can beclass ified into three broad categories depending upon the stage of real estate developmentthat each one of them is undergoing.





2. Architectural Aspects and Urban Development Today

As the historical development of high-rise buildings has already shown, theconstruction of edifices reaching higher and higher into the sky was – and to a certainextent still is – an expression of power and strength. This is equally true of bothecclesiastical and secular buildings: the power, strength and influence of entire families –i.e. their standing in society – is mirrored in the erection of ever taller buildingsculminating in a battle to build. The towers of San Gimignano are one of the best

preserved examples of this development. In many North African c ities, too, this attitudehas moulded the townscape for many centuries and will no doubt continue to do so in thefuture.

The names of the builders and architects have only been known since thehigh middle Ages around 1000 AD. They created new stylistic elements and added their“signature” to entire periods. Looking back, this makes it difficult for us today to decidewhether these master craftsmen shaped the various stylistic developments or whether anumber of master builders only became so well known because their work reflected thecontemporary fashion trends most accurately. That still holds true today, the only

difference being that tastes change very much more rapidly and “degenerate” into short-lived fashions. A building that reflects the spirit of the times when it is finished canappear “old” within only a few years. The brevity of the various stylistic trends is one ofthe reasons for the inhomogeneous appearance of modern towns and cities. Sincearchitects must expect that later buildings will have their own, completely differentformal identity, they do not see any reason why they should base their own designs onexisting standards, particularly as this would merely cause them to be considered“unimaginative”.

The points become clear if we take a closer look at modern trends in high-rise construction:

The dictate of tastes mentioned above is expressive of the egotism prevalent inmodern society with its desire for status symbols and designer brands.Unfortunately, the public not uncommonly bows to this dictate, as when towncouncilors set aside major urban development considerations and with seeminggenerosity set up public areas in the form of lobbies and plazas in high-rise

buildings.

The sheer magnitude of the projects forces all planners to adopt a scale totally outof proportion to all natural dimensions and particularly to the people concerned





when planning their buildings. In the past, urban development plans were easilydrawn up on a scale of 1:100 or at most 1:200, a scale which could still be directly

related to the s ize of a human being. With today’s h igh rise bu ildings, however, ascale of at least 1:1000 is required simply in order to depict the building on paper.This is illustrated by the example of the Sears Tower in Chicago: completed in1974, the Tower measures 443 m in height. Drawn to a scale of 1:2000, a human

being is represented by a minute dot measuring barely 0.9 mm.

In the past, it was the master builder and architect who defined the constructionand consequently the appearance of a building; today, on the other hand, technicaldevelopments determine what can and cannot be done; the appropriate and

basically essential symbiosis between engineer ing designer and artist has beenabandoned. This critical discourse on the architectural, urban development andeconomic background is not basically to cast doubt on high-rise buildings as such,

but it does illuminate some of the facets that are central to considering the risk potential inherent in high-rise buildings. This almost inevitably raises the questionwhy high-rise buildings should have to be built in today’s dimensions.

One reason is indisputably the need for a “landmark”. In other words, to expresseconomic and corporate power and domination in impressive visual terms. Nothinghas changed in this respect since the very first high-rise buildings were erected.

The steadily rising price of land in prime locations and an increasingly scarcesupply have made it essential to make optimum use of the air space. Prices inexcess of DM 50,000 per square metre are not uncommon for land in conurbationsand economic centres. Despite their height, however, high-rise buildings stilloccupy areas of truly gigantic proportions: the ratio of height-to-base width of thecubes in the 417-m-high World Trade Center.

However, high-rise buildings do little to prevent land beingsealed on a large scale. The suburbs of modern American cities are a prime example: as

far as the eye can see, the landscape is covered with single-family homes, swimming pools and artif icially designed gardens simply to provide sufficient private residentialland for all the people working in a high-rise building occupying only a few thousandsquare metres. Many of the techniques and materials which are also used for “normal”

buildings today would never have been invented and would never have becomeestablished if high-rise construction had not presented a challenge in terms of technicalfeasibility. Rationalized, automated sequences are beneficial to high-rise buildings; at notime in the past were such huge buildings erected in such a short space of time. Shortconstruction periods also mean shorter financing periods and consequently profits which





partly compensate for the additional costs incurred in the construction and finishing ofthe building.

3. Financing ModelsToday, the first question when it comes to design is still “how much does it

cost?” High Rise as a sample of high tech is assumed to cost a fortune. Many towersespecially in Europe and Asia have been designed with cutting edge technologies and

pioneering des igns. The first cost on those high rise struc tures could be substantiallyhigher than conventional budgets, such as Commerzbank in Frankfurt, Germany designed

by Norman foster and the SOM design of Pearl River Tower in Guangzhou China. TheGuangzhou project cost over eight times the Chinese national average for high rise

projects of its type, that is, 8,181.8 RMB/ m! compared to 1,000 RMB/ m!(95.05USD/SF).

Emerging Business ModelsReal estate itself is a regulated activity and is subject to a number of FDI restrictions.

These restrictions essentially result in a market where foreign investors with no Indian joint venture partner must invest a s ignif icant amount and undertake substantialdevelopment schemes with a limited ability to repatriate the funds in the short term.There is therefore a limited ability for a foreign company to make a tentative entry intothe market as a sole investor. This position has resulted in a number of business models

being used to facilitate investment.Four main market entry strategies have been adopted by foreign real estate players in

India: Large scale direct entry : With an independent approach for undertaking property

development schemes Establishment of an umbrella property development joint venture with a local

player in order to carry out numerous future projects Multiple joint venture approach where a number of ventures are entered into with

local partners each negotiated on a scheme by scheme basis and often with thelocal player placing land into the venture as equity

Investment into the Indian property market through the creation of a capital fund which in turn facilitates local developers.

Irrespective of the method of entering the market there are a large number of potentialmarket opportunities. Large and well publicised property development activity has taken

place in the principal areas of Delhi, Mumbai, Chennai and Bengaluru. In terms ofspecific sectors of investment, housing remains the single largest new constructionactivity whilst commercial office schemes, particularly for the IT sector have generatedsignificant opportunities. Organised retail although remains a relatively small sector by





the standards of most major economies, is growing rapidly and many industry observershave further identified the hospitality sector as an area set for future expansion.

Investment ModelsReal estate, being a capital intens ive sector, offers crossborder investors with several

investment opportunities. Post the sector opening up for FDI inflows have been typicallythrough multinational developers or financial institutions/ venture capitalists. Pure playfinancial investors are placing their money through strategic investments in projects/companies. The investment through financial investors comes primarily in the form ofopportunity funds, private equity and venture capital. Some of the prominent investmentmodels are as follows:





Private Equity/Re al Estate Funds (REFs)This is evidently the most preferred entry route for overseas investors. Currently

most of the private equity investments are directed towards unlisted real estate companieswhere the REFs purchase an equity stake and thereby partner in the growth plans of theunlisted firm. Primary reasons of preference for this entry route are the lower transactioncost and a potentially easier exit route, i.e. via a public listing. For example, TrinityCapital has acquired a 5.72 per cent stake in a Mumbai-based real estate company, D BRealty at an estimated cost of US$ 51 million.

Joint VentureWhile a few JVs are long term alliances for series of projects some of them are

project specific. The preference towards JVs by global developers is primarily to mitigatethe risk associated with entry in newer and emerging markets. The foreign developer

primarily contributes capital, engineer ing capabilities, brand, new constructiontechniques etc whilst the Indian partner brings in land, local knowledge on market,consumer and regulations and resources in the venture. Joint development is anotherexample of joint venture wherein the foreign investors set up an Indian presence andundertake development activity jointly. The Indian partners contribute land and receivedeferred consideration in terms of share of the development or share of revenues. Thoughthis was the primary route adopted for FDI, even now this arrangement is prevalentlargely for integrated townships or Industrial Parks. For example, MetroCorp Housing

Corporation has entered into a Joint Venture with Jurong International Group, Singaporeto develop an integrated township project worth US$ 116 million at Coimbatore.

W holly owned SubsidiaryA relatively less preferred arrangement few overseas developers are developing

projects on a standalone basis. Ascendas Pte, Asia’s leading total bus iness space solution providers , has a significant presence in India with a wholly owned subsidiary, AscendasIndia Private Limited.

Public Private Partnership (PPP)With the Indian Government undertaking several proactive initiatives in physical,

urban infrastructure development and encouraging private participation, the PPP mode isopening several opportunities for foreign developers. Further various public sectorenterprises are unlocking land value in prime assets held by them. With their opennessand interest in collaborating with foreign developers this is an added opportunity for anoverseas developer. In a recent development, DLF has entered into an agreement withKolkata Metropolitan Development Authority to develop an integrated township inHooghly District, West Bengal at an estimated investment of US$ 7.7 billion.





3.1. Cost-BenefitA real estate market shift doesn’t happen unless it’s profitable, and this shift

is no exception. A recent study completed by Lawrence Berkeley National Laboratory,the most definitive cost-benefit analysis of buildings ever conducted, concluded that thefinancial benefits of design are between $50 and $70 per square foot, more than 10 timesthe additional cost associated with building. The large positive impact on employee

productivity and health gains suggests that green building has a cost-effective impact beyond just the utility bill savings.

Buildings are generating a significant Return on Investment (ROI).According to the McGraw-Hill 2006 Smart Market Report, High rise generates 3.5%higher occupancy rates, 3% higher rent rates, an average increase of 7.5% in buildingvalues, and it improves ROI by 6.6% on average. High rise buildings are fetchingsignificant sales premiums. In Chicago, the John Buck Company spent US$270 millionconstructing the LEED-Gold 51-story 111 South Wacker Drive tower in the city’s Loopmarket. Completed in late 2005 when the Loop market was struggling with an 18%vacancy rate for Class A office space, the building leased up quickly to prestigioustenants. In January 2006, 111 South Wacker Drive was sold to a German 25 investmentfund for US$386 million, a $116 million profit, or a total sale price of $401 per squarefoot. Additionally, the building’s initial construction costs represent only 20-30 percent

of the building’s entire costs over its 30 to 40 year life (2030 Challenge, 2006), emphasisshould be placed on the “life cycle costs” of a public building rather than on solely itsinitial capital costs.

3.2. COST MODELS

The construction costs for high-rise buildings often run into hundreds ofmillions of dollars. The owner of the building will rarely be willing or able to bear thesecosts without outside assistance. On the other hand, however, debt service and exhaustedcredit lines will then constrict his operative freedom. Alternative financing models aretherefore frequently sought; the best known models are briefly outlined below.

3.2.1. LEASING

Leasing of buildings, particularly high-rise buildings, can to a large extent becompared with rentals. This alternative is commonly chosen when a company finds itselfin financial straits and needs cash. Selling the building – often a prestige object in a prime





location – to a leasing company is of two-fold advantage to the company: firstly, itacquires the urgently needed capital, and secondly, it can continue to use the building in

return for a monthly leas ing fee which, however, amounts to no more than a fraction ofthe purchase price received. The composition of corporate assets is changed by such atransaction. This can be a disadvantage when new loans are needed, for the building isthen no longer shown on the assets side as a property secured by entry in the landregister.

3.2.2. BOT

BOT stands for “build, operate and transfer” (there are other variations butthese will not be discussed in further detail here). In the case of this financing model, theowner of the land places his land at the disposal of a contractor who then erects a

building on it, such as an office tower. The owner of the land can exert a certain influenceon the planning and intended use, but does not share in the construction costs.

The contractor must organize the project’s financing himself, be it with ownfunds or with the aid of loans (“build”). In return, the owner of the land waives all orsome of the income from occupancy of the building for a certain period of time, usually25 years. During this time, the builder must obtain rents that are calculated to cover hisdebt service and draw a profit from the invested capital (“operate”). The builder’s risk

with regard to rents and debt interest is often considerable. At the end of the agreedoccupancy period, both the land and the office tower become the property of thelandowner (“transfer”). There are differences between these financing models: althoughthe BOT model grants the landowner the right to ownership, he is for a long timeexcluded from occupancy of the property. With the leasing model, the high capitalinvestment required is transferred to the lessor and the financing costs are replaced bymonthly payments akin to rent by the lessee.

3.2.3. DEVELOPER

The developer is a new profession born out of the explosive rise inconstruction costs which has been intensified by increasingly large buildings andstructures. This was triggered by urban renewal programmes and changes in taxregulations for large construction projects for which new financing models weredeveloped in the USA in the sixties and seventies. The developer usually draws up whatis known as a master plan for complete districts and then retains (usually prominent)architects to design the various components of the master plan independently of oneanother. The developer then seeks to find tenants or lessees for the building which at this





stage only exists on paper. Construction work begins when tenants or lessees have beenfound. La Defense in the Paris Basin is a typical example of such a development. This

suburb was created on the drawing board in the 1950s. A dilapidated district wasdemolished and completely redesigned. The traffic systems, such as Metro, urbanrailway, motorway and access roads were moved below ground level and covered by aconcrete slab 1.2 km long. Mostly office towers were erected on this slab with opensquares and green areas in between. The ensemble is rounded off by the Grande Arche dela Defense designed by the Danish architect Johann Otto von Spreckelsen and completedin 1989. The Grande Arche is a huge cube which is open on two sides with 37 officefloors and a height of 110 m equal to its ground lengths.

All the capital invested on the site came from private sources and wascontrolled by a public-law community of interests. In times of sluggish investmentactivity, however, it is not uncommon to find that only certain parts of the master plan areactually realized. Originally planned as a homogeneous townscape, the result is thennothing more than an unrelated fragment and areas that should have been filled with lifeappear to be deserted and uninhabited instead. In the mid-nineties London’s Docklands

provided a dramatic example of such a development: the transformation of the West IndiaDocks built between 1802 and 1806 resulted in what was for a while the highestmountain of debt in the world with the high-rise obelisk on Canary Wharf. After havingconsumed roughly US$ 3bn, the half-finished project was temporarily abandoned beforefinally being completed and let following a variety of financial transactions.

4. BARRIERS

4.1. Infrastructural Aspects

The different fates of La Defense and Canary Wharf are not (only) due to theextremely different planning periods of 30 years (La Defense) and 8 years (CanaryWharf), but above all to the manner in which the necessary infrastructure for the two

projects was tackled. In the case of La Defense, the entire necessary infrastructure wascompleted before the construction work actually started: underground railway lines androads, service systems were all planned and built beforehand. As a result, a fullyfunctional and above all adequately dimensioned infrastructure was consequentlyavailable when the buildings were taken into service. This made La Defense attractive toinvestors and tenants alike; the new district soon pulsated with life as an economicallysound basis for the entire project.

A jungle of political, economic and investment difficulties must beovercome for such prospective planning because the owner of the high-rise complex





bears no direct responsibility for the large majority of these far-reaching infrastructural measures. The project’s progress is consequently controlled by the municipal authorities,

as well as by supply and operating companies and not by the owner of the complex. Thesituation of Canary Wharf in London’s Docklands is exactly the opposite and proves thatthe La Defense type of planning is the economically more appropriate approach, despitethe associated delay in starting construction work and the longer preliminary financingrequired.

A second City of London was to becreated in the heart of the Docklands within theshortest possible space of time, with thousands ofsquare metres of tailor-made office space, hotels,shops and apartments for high-income tenants. Arail-bound fully automatic cabin railway known asthe Docklands Light Railway was to ensure thenecessary access. However, this transport systemfell far short of meeting the requirements, as itscapacity was far too low and it lacked the essentialconnection to the London Underground. The roadconnections for private traffic and public buses weresimilarly inadequate. This made the Docklandsunattractive to both commercial and private tenants.

An Underground link was finally built afterextensive planning and at the enormous cost ofroughly US$ 1.7bn; the road connections werelikewise improved at the cost of almost US$ 1bn. Only then did the precarious economicsituation of Canary Wharf improve. As these examples show, almost every high-riseconstruction project is doomed to at least economic failure if the infrastructure is notconsidered, planned and actually installed down to the very last detail.

4.2. ECONOMIC ASPECTS

Hundreds of companies and thousands of people depend on the smoothoperation of a high-rise building, from the one-man business of a newspaper vendor orshoe shiner and corporations with thousands of employees, such as banks, brokers orglobal players with a daily turnover in the order of several billions to radio, television andtelecommunications companies which use the roofs and tops of high-rise buildings for thetransmission and receiving installations. In addition, there are innumerable other

businesses and workers with their families whose economic situation is directly orindirectly linked with the high-rise building. These range from transport companies andcatering firms to tradesmen under long-term contract in the building. Nor should it be





overlooked that even the municipal authorities and the service companies are alsoaffected by the “failure” of a high-rise building and that its effects can be felt nationwide

or even worldwide in the worst case. This scenario not only applies to such total failureas a major fire or collapse of the building. Despite (or precisely because of) its size, ahigh-rise building is an incredibly sensitive and vulnerable system. Even a brief powerfailure can result in operational and economic chaos. The same applies to outsidedisturbances in the form of strikes by public transport corporations or a malfunction inthe underground or urban railway system.

4.3. SOCIAL AND ECOLOGICAL ASPECTS

Criticism today focuses particularly on the social and ecological effects ofhigh-rise buildings. The most commonly voiced reservations with regard to high-riseapartment blocks concern the social aspect. It is claimed – and there are probably anumber of studies to prove – that cohabitation in high-rise buildings does not work assmoothly as in homogeneous, historically grown districts with numerous small,manageable dwellings. The anonymity suffered by the people in these “residentialfactories” is criticized in particular – above all on account of the total isolation from otherresidents in order to avoid the stress of permanent contact. Organic, homogeneous

population structures with their positive effects on social conduct are rarely found and the

charge that high-rise apartment blocks are hostile to families and children is consequentlynot entirely unfounded.

Two diametrically opposed ghetto situations can eas ily ar ise in high-riseapartment blocks: since the costs for construction and maintenance of these buildings aredisproportionately high, correspondingly high rents must be charged, with the result thatthese blocks are more or less reserved for the well-off, while the socially weaker classesare excluded. Conversely, however, high-rise apartment blocks can rapidly cease to beattractive if compromises are made with regard to the building quality, maintenance orinfrastructure on account of the high investment costs entailed.

A building in disrepair will soon drive away the “good” tenants and becomea slum. The ghetto situation is intens ified when high-rise apartment blocks are built innewly developed fringe areas – far away from cultural and social centers – on account ofthe high cost of land in inner city areas. It is not without good cause that these areas arecommonly referred to as “dormitory towns”. Studies have also proved beyond all doubtthat criminal activity is promoted by huge apartment blocks and particularly high-rise

buildings. According to these studies, this phenomenon is attributable to the anonymity ofthe residents, as well as to the “pro-crime” environment with elevators, poorly litcorridors devoid of human beings, refuse collection rooms and bicycle garages, laundriesand above all underground parking lots.





It is a proven fact that considerably more murders, burglaries, muggings,rapes and other crimes are committed in such buildings than in residential areas with

smaller rented or private homes. Not only high-rise apartment blocks have a usuallynegative effect on people’s social environment: office towers are equallydisadvantageous. The vertical structure of the buildings simultaneously underlines thevertical hierarchy: the location of the office space becomes an indicator of a company’s“importance” and, if the company occupies several or all the floors in a high-rise

building, it may also be indicative of the employee’s standing in the company. Thecompany’s top executives reside on the uppermost floors with the best views; the floors

below provide a shield and every employee can positively see the distance betweenhimself and “them up there“. It is therefore not wrong to question whether high-riseoffice towers are really appropriate to modern organizational structures with theiremphasis on team work and interdisc iplinary cooperation. Excessive energy consumptionis a major shortcoming of high-rise buildings and one which could possibly lead to theirdemise one day. High-rise buildings are the farthest removed from the ideal form asregards energy efficiency namely the sphere, or the cube in the case of houses.

That applies to both heating and cooling: some skyscraper facades have to be cooled by day and heated by night in order to avoid undue stresses and the resultantdamage. The World Trade Center, for example, consumes some 680,000 kWh/dayelectricity for air-conditioning during periods of strong solar irradiation; the Messeturmin Frankfurt burns up energy worth DM 40 per square meter of useful floor space for

heating and cooling every month. A well insulated low-energy house, by comparison,uses energy worth less than DM 1 per square meter. The “energy balance” of high-rise buildings is also poor in other respects such as the water supply, which usually onlyoperates with the aid of booster pumps, as well as in terms of the disposal systems andoperation of the elevators, etc. From the point of construction economy in general, high-rise buildings will probably always be the poorest conceivable solution, from the

particular ly energy- intensive and therefore expensive construction as such to thedisproportionately high demolition costs.

Moreover, high-rise buildings are made almost exclusively of materialswhich a construction biologist would take great pains to avoid, namely concrete, steel,light metal, plastics and a wide variety of chemicals. Although subjectively unaware ofthe fact, the residents are frequently exposed to constant stresses in the form of pollutantemissions and electrosmog. High-rise buildings are sometimes described as microcosms;that is no doubt meant in a positive sense, but the reality is different. The people in ahigh-rise building are totally cut off from the world around them, from wind and weather,from temperature, from smells, sounds and moods. They live in an artificial world.

At the same time, however, the high-rise buildings also have a negativeeffect on the world around them, for they not uncommonly generate air turbulence anddowndrafts in their immediate vic inity; they can be a source of unpleasant reflections and





some adjacent areas remain permanently in the shade. Illuminated facades and large glassfronts are a death trap for many birds. The people outs ide the h igh-rise buildings also

often have the feeling that they are being observed or threatened by the possibility offalling objects. That fear is surely not entirely unfounded, for there have been cases inwhich parts of buildings, such as glass panes, have been torn out of their anchorage bystrong winds and injured or even killed people on the street below. Our love-haterelationship with high-rise buildings is finally also revealed in such recent box-office hitsfrom Hollywood as “Deep Impact”, “Godzilla” or “Independence Day”. It seems thattheir directors simply cannot avoid the temptation of reducing one of New York’s most

beautiful buildings – the Chrys ler Building – to a smoulder ing heap of rubble with thehelp of floods, monsters or meteorites. As a result, these skyscrapers more or less becomethe real stars of the film on account of their magic attraction and immediaterecognizability.

4.4 PLANNING and Scheduling

4.4.1.1 PLANNERS

The complexity of the trades to be coordinated has become several times

greater since then. Take, for example, the new block built for Südwest-Landesbank inStuttgart: many disciplines and different experts were involved solely in the project planning:

Architects Planning engineers for the supporting structures (engineering design and structural

analyses) Construction and site management (resident engineer) Planning of the technical building services (particularly heating, ventilation,

sanitation, cooling and air conditioning) Interior designers Planning and site management for data networks Planning of the lighting and materials handling Planning of the electrical and electronic systems Planning of the facades Surveying engineers Geotechnology, hydrogeology and environmental protection Design of outdoor facilities and vegetation Surveying of the actual situation in surrounding buildings





If we were to include all the contractors and specialists involved in the project as well, the list would probably be ten t imes longer. And if we then cons ider that

bankers, construction authorit ies, legal advisers and even advertis ing agencies or brokersmust also be coordinated in the course of the entire planning and construction of askyscraper project, it soon becomes clear that highly professional management isessential for such a project. Project management companies have come to play anincreasingly important role in recent years as they take over the entire organization,structurization and coordination of construction projects. They act as professionalrepresentatives for the client and embody the frequently voiced desire for the entire

project to be coordinated by a single partner.

SCHEDULING FOR HIGH-RISE BUILDING CONSTRUCTION USINGSIMULATION TECHNIQUES

SUMMARYHigh-rise buildings are commonly built in densely populated countries or urban

areas. A balanced floor construction cycle is critical for construction of the framestructures. The objectives in scheduling the floor cycle are to ensure smooth flows ofresources and to optimise the use of formwork and other materials. The floor area isusually divided into zones to allow the labour force and formwork materials moving

between zones. The preparation of the floor construction cycle would therefore be a

resources allocation exercise. However, the process is complex and difficult when it isdone manually. Floats are created deliberately in the schedule to ensure the balance inresources and to provide buffers. Simulation that can demonstrate the real worldoperations is an effective tool in handling this scheduling problem. This case studyexamines the constraints in planning the floor cycle and the effects of working period onthe overall schedule. Network based simulation model is used to investigate the

problems. It is noted that variations in working per iods have significant impacts on thetime schedule. A saving of 37.2% in time could be achieved when the working period isextended by 20%. The findings indicate that simulation can be used to assist planners toimprove their decisions and decide the strategies in scheduling and reviewing the floorconstruction schedule.

INTRODUCTIONHigh-rise buildings are still the essential form of building structure constructed

extensively in urban areas, in particular, in the hearth of the commercial zones ofmetropolitan cities. On the other hand scarcity of land supply encourages the constructionof high-rise buildings.

In scheduling the floor construction cycle, a simple approach is to adopt a constantduration for the construction of the typical floors. However, this always induces a false







Construction of a 42-storey buildingEach floor is divided into four zones. One set of steel wall form covering the

quantity of one zone and two sets of slab timber forms with each set covering the wholearea of one floor are used. In order to speed up the construction, precast façades andsemi-precast slabs are employed. The construction cycle aims at ensuring smooth and

balanced resource allocations between trade workers, concreting work and formworkinstallation. As a result the resources rotate horizontally between zones at the same floorlevel and move upward to the upper floor in the next cycle. Figure 1 shows the schedulefor a typical 6-day floor construction cycle including ten critical activities. The scheduleis prepared assuming that the activities are carried out at constant duration. However, theduration of activities varies due to factors such as supply of materials, skill of workers,weather and efficiency of plant and equipment.

On the other hand, material hoisting plays an important role in high-rise buildingconstruction. As the building ‘grows’, the transportation time increases and thus extendsthe duration for the crane-related activities. Researchers have studied and developed theoptimisation models for cranes aiming at reducing the transportation costs (Rodriguez-Ramos and Francis, 1983; Choi and Harris, 1991 and Zhang, Harris and Olomolaiye,1996). Leung and Tam (1999) developed prediction models for improving the predictionof hoisting times. One of the objectives of this study is to use the simulation technique toreview the typical construction floor cycle.

SIMULATION MODEL FOR TYPICAL FLOOR CYCLE The building up of simulation models requires planners to have a good knowledge

of simulation. A network based simulation has been used in this study. This simplifies theskills and knowledge required for modelling a simulation network as general simulation

programme can be difficult for general users. Planners who have the knowledge inconstructing critical path network and bar charts could be able to use the simulationmodel. The constructing of simulation network for modelling is similar to the critical pathnetwork using the ‘activity on node’ format except that loops are allowed to show the re-cycling of resources. During the simulation process, the activities may either in an activeif the constraints are met or otherwise in an idle mode. The typical construction floorcycle shown in Figure 1 can be easily developed into a simulation network as shown inFigure 2.

Although only one floor cycle is shown in the network, it covers the activities inthe four zones, which are handled within the simulation algorithm. The ten activities arescheduled in a sequential order. Two loops are teed off from the main network indicatingthe dependence relationship between installation of precast façade, the activities for wallconstruction and crane-related activities. Normally, a tower crane can only be installed





for a building block owing to both economic reasons and space availability. Therefore,the crane can only serve one activity at one time and it is important to optimise the usage

of a tower crane which is one of the critical resources in high-rise construction.

A ‘Start’ and ‘Stop’ node is assigned in the network for controlling the numbers ofsimulation. During the simulation process, activity boxes are attached with a colouredspinning icons showing their status. Resources shared by activities can be represented bygraphics moving between the activities boxes.





SIMULATION FOR TYPICAL FLOOR CONSTRUCTION CYCLEIn order to optimize the duration of a floor cycle or to determine the daily

schedule, modellers can modify the duration of the activities to suit the site conditions. Ithas to point out that the duration of the activities can be shortened or extended by

increasing or decreasing the input resources, mainly the human resources in concreteframe construction generally. Table 1 shows the duration for the activities of a typicalfloor construction cycle.





In order to generate realistic results, the duration assigned for the simulation hastaken into account the effects on hoisting times due to variations in hoisting height. Forexample, the hoisting and fixing of eight precast façades takes about 51 minutes at thelower floors and 75 minutes at the upper. Planners can adjust the duration if they identifysignificant differences between the original input and the actual site condit ions.Alternatively, planners can carry out simple work study techniques on site to collect datafor predicting the hoisting time.

Apart from modifying the duration to suit the dynamic site conditions, planningengineers can review the effects of working hours for a working day to a floor cycle.Examining the standard floor cycle shown in Figure 1, it is evident that there are idlingtimes in the schedule. The idling times are created for levelling the resources. However,manual resource levelling is complex and difficult and optimum solution cannot be easilyfound. The numbers of working hours for a working day can be input as a constraint inthe simulation. In Hong Kong, most of the residential areas are densely populated and thegovernment has imposed stringent noise control ordinance to restrict the working hoursfor using noisy construction plant and equipment. The normal working period to whichthere is no restriction is between 7:00am and 7:00pm. On the other hand, the normalworking hours for the building industry lie between 8:00am and 6:00pm. Any time

beyond the normal working hours, the trade workers need to be paid w ith an overt ime

allowance of 50% of their basic wages. It is vital to minimize the labour costs whilemeeting the programme of the project. In this study, four working period scenarios have been reviewed by using the simulation model. The summary of the simulation results isshown in Table 2.

In the four scenarios, the first working period follows the industry normal workinghour and constant activity duration was used. The remaining scenarios have been testedwith stochastic activity duration. The simulation results confirm that the first scenario isworking approximately on a 6-day cycle. However, it is noted that there are significantsaving in time when the durations of activities are varied. In the second scenario, there is





a saving of 25.8% even the activities are scheduled within the normal working period.However, when the working period is extended by one hour in the third scenario, further

decrease in time is minimal. In the last scenario, the working period is extended by twohours; a further saving of 11.4% (a total saving of 37.2%) is yielded. It means that theincrease of the working hours by 20% is not effective since the labour costs will beincreased by 40%. This is a typical time-cost trade off problem when time is approachingto the crash time solution.

SELECTION OF APPROPRIATE WORKING SCHEDULEThe simulations described above provide alternatives for planners to make

decisions on initial scheduling and subsequent updating. The simulation results enable planners to locate the upper limit of the floor cycle, ie approaching to the crash timesolution. However, it is a general rule in planning that the normal time should be used inthe planning stage unless the project duration would have already been overrun. Anaggressive project manager may consider applying the second scenario in order to shortenthe frame construction by 62 days (ie. 40 x [ 6.0 – 4.45]) without spending overtime

payments. If the project is undergone delay, a more drastic decision will be to extend theworking period by two hours as if in the fourth scenario. Therefore, when deciding theappropriate floor cycle duration, planners have to review the factors and the merits priorto determine the strategies.

This case study examines the application of simulation techniques in evaluatingand scheduling the floor construction cycle of a high-rise building. The typical floorconstruction cycle is always the main concern of planning engineers. The earlycompletion of the floor s labs releases working areas for the subsequent activities.

The initial planning and the subsequent re-scheduling are therefore important forthe successful management of a high-rise building project. The traditional schedule for atypical floor aims at balancing the resources, in particular the formwork system, to assurea steady movement of resources while maintaining the progress. Simulations for the floorcycle using stochastic duration and different working period had been conducted in thisstudy. The simulation results generated show that the duration for the floor cycle could beshortened by 25% to 37%. The shortening is achieved by reducing the idling time of theresources. In deciding the duration of the f loor cyc le, planning engineers have to considerthe project budget because additional overtime costs for labour would be incurred. Thesimulation results could provide useful information for planners to decide upon theirstrategies in scheduling a typical floor construction cycle at different stages of the project.





5 Regulations and Directives

The various laws, regulations, directives and standards in force must betaken into account when planning and erecting a building. The planning engineers arealso obliged to observe what are known in India, for instance, as the “generally acceptedtechnical rules for construction“; in other words, generally applicable technical and traderules must be taken into account and observed in addition to the standards andregulations.

Although each country has its own regulations and directives governing theconstruction of high-r ise buildings, they are all bas ically similar in content with a fewdifferences depending on the local circumstances. It is standard practice in somecountries to base the bidding and planning phase for projects on foreign standards(particularly on the American ANSI Codes and UL Standards, British Standards or theGerman DIN standards) or to include various elements of these foreign standards in thenational system of standards. As a rule, these regulations are primarily designed to ensure

personal safety and then to protect the building aga inst damage and defects. In addition tothe requirements imposed by public authorities, there are also requirements imposed byinsurance companies with the aim of ensuring greater protection for property.

REQUIREMENTS FOR HIGH RISE BUILDINGS:





1. High Rise buildings / Complexes shall not be allowed in Congested areas/existingareas and settlement areas/ Abadi /Gram khantam areas.

2. The minimum size of plot for High Rise building shall be 2000 sq. m.

3. In respect of sites proposed for high rise buildings and affected in road wideningwhere there is shortfall of the net plot size, upto 10% of such shortfall in net plotarea would be considered with the proposed height and corresponding minimum allround setbacks.

4. The building bulk, coverage and height shall be governed by the minimum alroundsetbacks to be left, the organized open spaces to be left and the height restrictionsimposed by the Airport authority (if applicable) / Defence authorities (ifapplicable) and Fire Services Department and the City-level Impact fee on built uparea required to be paid, as applicable.

5. Prior Clearance From Fire Dept. and Airport Authority:For any High Rise building located in vicinity of airports as given in the

National Building Code, the maximum height of such building shall be decidedin consultation with the Airport Authority and shall be regulated by theirrules/requirements. Interstitial sites in the area which are away from the

direction of the Airport Funnel zone and already permitted with heights cleared by the Airport Author ity shall be permitted without referring such cases to theAirport Authority.





6. Every application to construct or reconstruct a High Rise building or alteration toexisting High Rise building shall be made in the prescribed form and accompanied

by detail plans floor plans of all f loors along with complete set of structuraldrawings and detail specifications duly certified by a qualified structural engineer. Necessary prior NOC shall be submitted from the Airport Authority (if applicable)and Directorate of Fire services, along with the application.

7. The minimum abutting road width and all round open space for High rise Building/ Complex shall be as follows:





7.1 The abutting road has to be black-topped with minimum 2 –lane

carriageway. Service roads where required as per these Rules, shall beminimum 7 m wide with minimum 2-lane black topped carriageway.

7.2 For upper floors from 2nd floor onwards, balcony projection of up to 2 mmay be allowed projecting onto the open spaces.

7.3 The open space to be left between two blocks shall be equivalent to the openspace mentioned in Column.

7.4 It is permitted to transfer upto two metres of setback from one side to theother side, which needs to be uniform at any given point, subject tomaintaining of minimum setback of 7 m on all sides.

7.5 Where the lighting and ventilation of a building is through the means of achowk or inner courtyard or interior open space/duct, such open space shall

be open to sky and of area at least 25 sq m and no side shall be less than 3 m.

8 TOWER AND PODIUM TYPE HIGH RISE STRUCTURE may be allowedwith the following:

8.1 For podium, i.e., Ground plus first floor: alround setbacks shall be 7 malround8.2 For the Tower block: The maximum permissible coverage and minimum

alround setbacks shall be 50 % of the Podium Block, and shall be at least 3mfrom the Podium edge.

8.3 The fire safety and fire escape measures for the Tower Block shall beindependent of the Podium Block.

9 “STEPPED TYPE” OR “PYRAMIDAL TYPE” HIGH RISE STRUCTURE

Such type of high rise building may be allowed with the following open spacerequirements:

9.1 At ground level : Minimum 9 metres alround open space for the first fivefloors

9.2 At upper floors: increase of 1 metre alround open space or more, for every 5upper floors or 15 m height or part thereof, over and above the ground levelopen space of minimum 9 metres.







Such buildings shall be planned, designed and constructed to ensure fire and safetyrequirements are met and maintained and shall comply in accordance with the Fire

Protection Requirements of National Building Code of India. The facilities for providing fire protection and fire fighting facilities in such buildings shall be in compliance with the stipulations laid down and clearanceissued by the Fire Department from time to time. NOC from the Fire Departmentshall be obtained from time to time regarding the fire safety requirements andfacilities installed. The designs and installations regarding fire protection andsafety measures including exit requirements and smoke containment and smokemanagement measures shall be undertaken through a fire engineer / fire consultant.

Compliance of the parking requirements shall be as given in these rules. The parking facilit ies and vehicles driveways etc. shall be maintained to the satisfactionof the sanctioning Authority.

Such buildings shall be provided with solar water heating system in the buildingand solar lighting in the site for outdoor lighting, etc. and give a bank guarantee tothis effect to the sanctioning authority for compliance of the same.

All High-Rise buildings with covered area above 300 sq m shall be designed andconstructed to provide facilities to the physically handicapped persons as

prescribed in the National Building Code of India,2005. In all buildings irrespective of above height provisions, the requirements of parts of

the building like size and area requirements of habitable rooms, kitchen, bathroomsand Water closets, other areas, corridor and staircase widths, service ducts, etc.shall conform to the provisions of the National Building Code of India,2005.

All environmental aspects like provision of Rain water harvesting structures,greenery, solar heating and lighting systems and provisions of the Andhra PradeshWater, Land and Trees Act 2002 shall be complied in such of the sites andSchemes where these are applicable.

Notwithstanding anything contained in these Rules or any other orders, the minimumclear setback on the sides and rear sides of any high-rise building under any

circumstances and in cases where a concession or incentive is availed in terms ofsetbacks shall not be less than 7 meters, and such minimum setback area shall be clearwithout any obstructions including balcony projections, to facilitate movement of firefighting vehicles and for effective fire fighting operations.





Park ing space





In case of high r ise buildings parking space may be provided in the set back afterleaving a minimum setback of 6 Mtrs alround the building to enable movement of

Fire Tender. Alternate means of parking such as terrace parking, multi stage parking, parkingsilos may be permitted, subject to production of NOC’s from the Authorities (incase of high rise buildings). In such cases, a clear height of 3.6 Meters in the

basement floor has to be provided, and the space to be earmarked per unit of Car parking may be determined by the authority.

Parking in the upper floors can be allowed only if ramps are provided after leavingthe minimum setback line to reach such floors.

Ventilation shaftFor lighting and ventilating the space in water closets and bath rooms, when no

opening is provided towards any open spaces, they shall open on to the ventilating shaft,the size of which shall not be less than as indicated below:

Exit requirements for high rise buildings, public and industrial buildings

Every building meant for human occupancy shall be provided with exits sufficientto permit safe escape of occupants, in case of fire or other emergency.

In every building for multi family dwellings and all places of assembly, exits shallcomply with the minimum requirements of these bye-laws.

All exits shall be free of obstructions. No building shall be altered so as to reduce the number, and size of exits to less

than that required. Exits shall be c lear ly visible Routes to reach the exits shall be clearly marked and

signs posted so as to guide the persons using each floor. Wherever necessary, adequate and continuous illumination shall be provided for

exits.





Fire fighting equipment shall be suitably located and clearly marked. Alarm devices shall be installed to ensure prompt evacuation of the persons

concerned. All exits shall provide continuous means of egress to the exterior of buildings or tothe exterior open space leading to a street.

Exits shall be so arranged that they may be reached without passing throughanother occupied unit.

Number of exits The location, width and number of exits shall be in accordance with the travel

distance, capacity of exits and the population of building based on occupant load; There shall not be less than 2 exits serving every floor for buildings of 15 mtrs

height and above and at least one of them shall be an internal stairway.





SAFETY IN HIGHRISE

5.4 FIRE PROTECTION AND OPERATIONAL SECURITY

Many of the construction regulationsconcern fire protection. There can be manythousands of people in a high rise building at anyone time. If a fire breaks out, they must all be ableto leave the building in the shortest possible spaceof time and without risk of injury. This is whyregulations concerning the number and executionof escape routes and fire escapes, firecompartments and the choice of materials must beobserved Operational security encompassesregulations governing the safety of elevators andescalators, the execution of stairs, railings and

parapets or the installat ion of emergency light ing. Some regulations also include CO2alarm systems for underground parking lots; indeed, there are even regulations governingthe non-slip nature of floor coverings in traffic areas, sanitary rooms and kitchens.

5.4.1.1 STABILITY AND CONSTRUCTION PHYSICS

The regulations governing the stability of a building are usually met by therequisite structural analyses. In addition to demonstrating the internal structural strengthof the construction and safe transfer of loads to the subsoil, the stability calculat ions mustalso include poss ible deformation due to thermal expans ion, w ind loads and live loads ordead weight, for example. This is closely related with demonstrating the safety of theconstruction, for instance by taking steps to limit the (unavoidable) cracks in concreteelements.

5.4.1.2 PROTECTION AGAINST NATURAL HAZARDS

The regulations and directives governing protection against natural hazardsare usually closely associated with the demonstration of stability. Windstorms andearthquakes are the most serious natural hazards for high-rise buildings. As a rule, theassumed loads and design rules for the “load cases” of earthquake and windstorm will be





specified by the regulations in order to ensure that the building will withstand windstormsor earthquakes up to certain load limits. At the same time, this will serve to rule out the

risk of bodily injury due to falling parts of the building, especially parts of the facade.

5.4.1.3 SOCIAL ASPECTS AND PROTECTION OF THESURROUNDI NGS

The regulations governing social aspects and protection of the areasurrounding high-rise buildings are designed above all to prevent any indirect risk orthreat to people. Such regulations may concern planning aspects, such as the minimumdistance between a high-rise building and neighbouring buildings, or they may take theform of rules defining the maximum permissible influence that a building can have on themicrocosm surrounding it. Depending on the location of the high-rise building,corresponding statutory instruments may also govern the effects on air traffic safety orthe building’s influence of radio communications.

This exceedingly concise outline of applicable regulations illuminates onlysome of the rules to be observed when building a skyscraper. If all the regulationsgoverning high rise construction were to be stacked one on top of the other in printedform, they would themselves be as high as a multi-storey building.

4.4. TECHNOLOGY OF HIGH-RISE CONSTRUCTION

5.4.2 Layout and Space

Layout and Space design is the cadenza of a symphony to the architects. Agreat design can significantly improve the sustainability of the high rise.

5.4.3 Service core

The size and location of the service core in a high rise building play a predominant ly part in the whole design. That is well stated by Ken Yeang in his HighriseElevator Cores (2002). He believed the arrangement of primary mass position can help toshade or retain heat within the building form. Of the various possible service-core

positions i.e. ‘central core’, ‘double core’ or ‘single-sided core’, the double core is to be preferred. The benefits of a peripheral service core position are:

No fire-protection pressurization duct, resulting in lower init ial and operation costs





A view out with greater awareness of place for users Provision of natural ventilation to the lift lobbies ( and thus further energy savings)

Provision of natural sunlight to lift and stair lobbies A sager building in event of total power failure Solar buffer effects and/or wind buffer effects Winter gardens allow vast amounts of light deep within the building and provide Pleasant views to those working deeper within the building. Creating a central atrium space in a high rise building Centralized core area for circulation, mechanical, and other basic building needs. The core functions were pushed to the outer corners of the building to make way

for the atrium space.

Winter gardens had to be rotated around the facade of the building. The central atrium, free of structural members, was essential to provide light bothvertically, from the glass roof at the atrium’s top, and horizontally, from the wintergarden facades to the office across the atrium

Role of Tower Cranes in High Rise Structures

India is witnessing construction of large number of high rise structures including

tall buildings up to 320m height, power station chimneys (275m high) and NaturalDraught Cooling Tower (180m high). The use of tower cranes in all such cases is anabsolute necess ity. While some tower cranes are being manufactured/ assembled in India,cranes to service upper end of the spectrum are being imported.

Tower cranes now-a-days are sophisticated items of construction equipment,requiring detailed planning in procurement and utilization. They are electrically operatedand come with wide variety of options in terms of working range, jib arrangement, massconfiguration etc .

Use of tower cranes in India started modestly in the Sixties. Tower cranes werethen imported. Today the population of tower cranes in operation in India is in thousands.A fac tory in Pune was setup by a multi-national manufacturer of tower cranes for use inIndia, Middle East and Far East. In addition there are couple of factories setupindigenously to manufacture tower cranes.

Electronics on the advanceElectronics is now extensively used for the operation of the tower cranes. The

starting point has been in the use of Programmable Logic Controllers (PLC). Thesecontrollers make sure that the various operating parameters like hoisting, trolleying andslewing are displayed to the operator. Another development is the variable frequency





drive for var ious operations listed above using simple squirrel cage motors. Thistransforms the standardized three phase supply network into a net with variable voltage

and frequency. This means the motor can continuously absorb every revolution, workingto full capacity even in the part load operational range. The crane can be positionedsmoothly and accurately. Hoisting speeds are increased and with that turnover capacity.The motor does not require high starting current which to certain extent reduces theconsumption of energy.

A recent milestone is the operational add-on module of radio transmission ofmachine data. This makes constant on line monitoring and evaluation of the crane data

possible and allows for fast diagnosis and trouble shooting in the case of breakdowns.

Flat top tower cranesThe first trolley jib crane with a compact top was introduced in the Nineties. This

is an advantage when several cranes are swivelling on-site at the same time and whenheight res triction applies, for example airports. While there are advantages of lesser spacerequirements, problem includes the necessity for erection of full jib in one operation andconsequent requirement of space and higher capacity crane required for erection.

Tower crane – Brief DescriptionTower crane is the only type of crane spec ially des igned for buildings and other

high rise structures. They can distribute material for whole plan area of a tall structure.

Tower cranes can be fitted with a derricking jib or horizontal jib with traversing trolley.A derricking jib is necessary if required to be raised to clear obstructions. A horizontal jibis easier to operate, is faster and has lower power consumption.Tower cranes can be rail mounted but require properly laid level track; the travel is alsoelectrically operated. Other options include fixed base tower crane or climbing towercranes when attached in the height to the frame work of the building. In such cases thedesigner of the building should permit attachment with resultant loads, at appropriate

points. With winches of higher capacity, the maximum height of the attached crane can be increased.

Site conditions regulate the height of the unattached crane depending uponexposure to high winds etc. The fixed base may involve substantial area and depth ofconcrete. Cabins are usually on top of the mast and jib slews either with the mast oraround the mast. Control is usually by the operator; remote control is also possible. Thecranes are usually electrically operated.

Climbing CranesThe mast climbs with the building being erected. The maximum height to which

these can be used is dependent only on site condition where wind pressures can seriouslyaffect the load and the type of load handled. A world record has been created during the





construction of the tallest building in the World (Burj Dubai); climbing tower cranes have been used for building height of more than 600m. the design of the building is an

important element in the economics and efficient use of climbing cranes. Such cranes can be located in lift shafts and service wells. The permanent structure must be sufficientlystrong for the crane reaction. The control of the climbing crane is usually remote.

Choosing the correct type of craneTower cranes feature a high maneuverability, a large space below the crane and

high arrangement of the boom which can pass over the erected structures.The type and number of cranes to be used will depend on the plan, size and shape

and the height of the building and the access spaces around it. Where the tower crane islocated outside a high rise structure, it has to be often tied to the structure at intervals tostabilize the mast. The structure assists in taking up the reaction at a certain points, inwhich case the structure has to be designed for the stresses generated by the anchors.Mobile tower cranes are subdivided with respect to their running gear into rail mounted,truck, wheeled, and crawler cranes. Most widely are rail mounted cranes, they are simplein service and ensure a high safety.

Cranes employed in construction have a lifting capacity of 3 to 25 tonnes and amaximum swingning radius is 90m. separate motors are used for hoisting, travelling,luffing, traversing etc. Stationery Cranes are mounted on a foundation and they serve theconstruction site from one point. Climbing tower cranes are usually common in the

construction of multi –storied and high rise buildings.Where access around the site is restricted, a tower cranes might be used internally by leaving out the floor panels or making use of the lift shaft or stair well. Thus it is possible to poperate from a more central point in the structure and makes most use of itsreach. Alternatively, a c limbing crane may be more economical. A disadvantage whenthe lift shaft is used is that the lift installation is delayed pending removal of the crane.However, it is possible to construct the lift lining and assemble from the bottom up,following the passage of the crane.

Avoid ScaffoldingFor maximum speed and economy, where the cranes are installed, the use of

scaffolding should be avoided as far as possible and external elevational work shall bekept to a minimum. In such a case pre glazed windows and designed c ladding panels or

proprietary curtain walling which can be fixed from inside, can be used. Many cantileverunits, stairs or intricately shaped concrete items are best pre-cast.

Tower cranes and plan shape of buildingInternal or fixed external tower cranes are suitable for square and ‘Y’ or star

shaped plan buildings. For long and narrow buildings, a rail mounted travelling crane





may be used. For cluster of low raised buildings, a tyre mounted self erecting tower craneis most appropriate. Such cranes are light in weight, with a generator mounted on base

frame. The erection as well as holding up is computer controlled and takes less than onehour. Such self erecting tower cranes are available with mast height up to 25m and jiblength of about 30m.

Erection and commissioning a tower craneA specialist group with knowledge of erection and commissioning the tower crane

should be employed in order to optimize the operation. The fountains, where required,should be cast in advance after obtaining the drawings from the manufacturer. Using acrew with optimized training, the erection and commissioning of a typical tower craneshould be completed within three days. In the absence of trained crew and management,it may take up to one or two weeks to erect and commission the centre. A mobile crane isrequired to assist in erection of a various components of the tower crane. For towercranes of large capacities, a 100t. capacity mobile has been used.

Rail trackProper performance of the crane is dictated by the state of the rail track. The gauge

and specification for the rails are normally provided by the tower crane manufacturer.Concrete sleepers are normally used. The maintenance of the rail track during the serviceof the tower crane similar to that of a rail line passing high speed trains.

Control and Safety DevicesTo ensure safe operation and better use of cranes, they are fitted with safety and controldevices and instruments.

AnemometresPressure due to high winds may force the crane to derail or collapse. Wind pressure

is determinted with anemometers where a crane operator ca n read the wind velocity.Cranes are safe to operate in wind velocities up to 40 Km per hour. PLC devices assist inautomatically shutting down the crane when the wind velocity is exceeded.Limit switches are used in cranes to limit the hoisting height. Safety to restrict the canetravel. Swinging radius indicator is secured on the jib. The scale can be graduated toindicate not only the jib radius, but also the safe loads that can be handled at the givenradius.

Components of a typical tower craneThe various components are indicated in the fig.1. The major components are : the

mast, the jib, the trolleys, hoisting, s lewing, luff ing and lowering mechanisms. The mastis in sections, convenient to handle during erection and dismantling (usually 3 to 6





metres). Sections are connected by pin or bolted joints. Special torque wrenches arerequired in the case of bolted joints and are usually supplied along with the crane.

Erection and Dismantling of tower craneThese are specialized activities and are required expert guidance. In particular, the

method of dismantling the tower crane from the top of the high rise structure requirescareful planning and tools. This is usually planned by the supplier of the crane who also

provides the necessary fixtures for dismantling purposes. The intermittent anchoringsystems by guy ropes for very tall structures are also carefully designed by manufactures.The designer of the permanent structure should interact with the manufacturer and ensurethat the permanent structure is not taxed beyond its designed stress limits. Sometimes itmay be necessary to locally strengthen the structure around the anchorages by additionalreinforcement, higher grade of concrete etc. so that the construction speed is notcompromised.

Safety in Erection, Commissioning, Use and Dismantling Tower CranesThe first requirement is to have qualif ied, trained and exper ienced operator. Indian

project sites do not give adequate attent ion to th is aspect, resulting in inefficientoperations, avoidable accidents, work-down time, causalities etc. the operator shouldhave adequate language skills for reading the operation manuals and following them.Minimum qualification should be at least ITI certificate. It is paradoxical that in real life

situation, the contractor spends a few crores on purchase of tower crane and selects anunqualified operator, who had not even passed 8 th standard!Some of the ITI certificate holders may also not be proficient in English; it is

desirable that the operations manuals are printed in the local language in addition toEnglish. If this service is not provided by the equipment manufactures (normally theyshould provide), the end user should get the translation done in one or two prominentlanguages and provide the copies to the operators.

The tower crane operators must have read the operations instructions in particular,the chapters concerning safety. The personnel must wear safety clothing/ protectiveequipment during maintenance/ repair work. They should not wear loose and long hair,loose clothing, jewellery etc.

Repairs and adjustments must be made only by qualified and trained mechanics. No modifications shall be a llowed to be made without the consent of the manufacturer.The rail track should invariably on concrete foundations and not on timer sleepers. Therail track foundation details should be obtained from the manufacturer. While not in usethe boqie should be locked to the rail and the jibs should be free to rotate. The hookshould be raised and locked to the jib trolley. The tower crane should not be operatedduring high winds with speed exceeding 40 Km. per hour. The crane should not betravelled with load. The jib should not be slewed by more than 360 Degrees.





While traversing, the limit switches should restrict movement of trolleys to withinthe operating range of the jib with automatic slow down at both ends of jibs. Limit

switches should control the hook movement so that the hook dose not hit the ground orthe jib. Similarly limit should be used for slewing a maximum of 360 Degrees withautomatic slow down at the end of the movements.

Various electronic limit switches are provided as standard fittings to the tower crane: Hoist limit switch Slewing limiter Trolley limit switch Travelling limit switch

Load limiters Moment cut out High speed and maximum safe working load cut outs

Various audio warning and indicator lights are provided in the operators cabin On Power indicates crane is energized On indicates crane in service Load and dynamic moment indicates load and dynamic moment achieved Fault Hoist indicates malfunctioning of the hoist winch

Fault slewing indicates malfunctioning of slewing Fault trolley indicates malfunctioning of the trolley winch Hoist limit Switch avoids possible driving errors. It allows to stop the hoisting

motion as soon as the pulley block comes near the jib trolley. When lowering, itforbids the rope to unwind completely and wind up onto the drum in the reversedirection.

Trolley Limit Switch avoid possible driving error by stopping the trolley motion before reaching the stops at the jib foot and jib nose.

TrackUse slightly worn rail for good bearing surface. Rails should be absolutely parallel

and well bedded down on a solid base. Tracks should be earthed. It should be perfectlystraight, unless otherwise designed. Use same type of rail throughout.Fit rail stops at least 1m before end

A travel limit switch A spring stop (buffer) A fixed stop, welded to the rail





Counterweight (Ballast)Base: Reinforcement concrete blocks. The reinforcement and hooks for hoisting

and hanging the blocks should be designed for safety. Paint the weights on the side of blocks.Erection- Safety

Do not work with overload Use slings in good condition Erect in the order indicated Fit the counter jib & jib parallel to the track Fit rail clamp & wedges on rails Examine pins. Some are made to manual.

Telescoping operations according to manual. During rais ing, DO NOT- slew the jib, move the trolley or carry out anyhoisting/ lowering

Telescoping only if wind speed < 40 Km/Hr.

Safety during OperationCheck loads to be lifted/ working heights, permissible wind speeds, loads with

more than 1 sq.m. /ton, surface area exposed to wind. When several cranes are workingclose together the distance between two cranes must be at least 2m longer than the lowest

jib likely to meet the mast of the other machine. Alternat ively anti collision devices must be used.

FORMWORK FOR HIGHRISE CONSTRUCTION

SLIP FORMSSlip forming was introduced into Australia around 1952, mostly for silo

construction. It has been in use overseas much longer. A slip form is made so that it canmove slowly whilst being continually kept full of concrete. The form is not deep and itmoves so that concrete is not in the form for long. The concrete is left behind by the form

when it is just strong enough to support itself.Typically, the concrete stays in a vert ical s lip form for 1.5 - 6 hours. In horizontal

slip forming, as in forming the kerb of a roadside, the concrete can be exposed sooner.Because the form is continually filled it produces jointless concrete. That's useful forconstruction of containers, such as water tanks, silos, cooling towers and reactor shieldswhere breaks in the concrete must be avoided. It is also used in the construction of tallstructures such as lift wells, where the surface needs few spaces or protrusions.

It has been used for many years in the construction of tall buildings which have flatwalls and the same dimensions all the way up It is also very good for circular structures





which have changing dimensions, such as cooling towers because the size of the form can be changed as it moves. The height of a vertical slip form can range from about 1 m to 2

m with the most common size being 1.2 m tall. The surrounding supporting structure andwork platforms add to the size of the structure. A schematic diagram of a vertical slipform is shown below.

Slip forming is suitable for round the clock pouring and so structures can be built quitequickly. Typically, slip forms rise at about 30 cm per hour, allowing a tall structure to be

built in d ays. Horizonta l slip forms, such as in those used for forming of water or roadsurfaces, move along more quickly. Hundreds of metres, even kilometres per day and can

be achieved.





Components of Slip forms

Slip-forms are special structures. They are specially designed by engineers for specificconstructions.The structure consists basically of five parts:

form face and its supports; yokes and cross members; jacking equipment which keeps the form moving; work platform at the top level of the form; and; hanging work platform, below the form face where the workers finish the surface

as it exits the form.

Drawings of the forms will indicate the spacing walers, the design of the yokes, thework platforms and the jacking mechanism.





The height of the form will depend on the temperature, the type of concrete used and itshardening rate. In cold climates, a taller form is used which allows the concrete to be in

the form longer, allowing it to harden. Slip forms can be made from proprietary panels ifthe job is a standard one where such panels can be used. It can also be designed to become bigger or smaller as it rises producing a bigger or smaller structure.

CALCULATI NG MATERIAL QUANTITIESThe most important calculation in the design of slip forms is the length of time theconcrete needs to be in the formwork. When you know that, the rate of rise can beadjusted to suit.The time (T) that the concrete spends in the slip form is calculated from the formula:

T = [D - (F + t + t' + L)] / R





Where the letters refer to the diagram:

D is the depth of the formR is the rate of rise of the formF is the free boardL is the distance between point of separation and toe of the formt is the thickness of layer of fresh concretet' thickness of the next layer needing revibration. This is usually considered to be aquarter of the fresh layer.

Advantages of Slip forms:Slip forming is best used when there is little need to change the formwork for large

buildings and there are few changes in dimension. Even though the formwork is complex,takes a long time to set up, and needs a lot of labour at the time of the slip, the time takento complete the job is small. The costs are higher in setup but reduced overall due to thespeed of completion.

There is a minimum height of construction of about four floors, above which thecost of slip forming becomes economical. Slip forming is a good choice for a tall buildingcore, but not so good for a three storey lift-well. To build a special slip form that

probably won't be used again will be more expensive than using standard panels whichare cheap and easy to erect.

Before choosing slip forming some of the things to consider are: The concreting will take place in a very short time. The init ial setting up time ins itu will be longer than for conventional forms but can

be reduced by construction of the forms in large slabs off site. The cost per square metre of the equipment will be more than for conventional

forms. Labour costs will be higher due to shift work but productivity will be good. There are no construction joints. The process is less weather sensitive than other methods. Working platforms can

be covered from the weather and the surface of the concrete can be protected. Standby plant and workers are needed. It is easy to obtain a good key for subsequent finishes. The final tolerance for the completed work is about same as that for other methods.

Spiralling and non verticality have almost been eliminated. Economising on the design of the slip form may lead to major and expensive

problems.





CONSTRUCTION TECHNIQUES:

Core Wall Survey Control System for High Rise Buildings .

In recent years there has been considerable interest in the construction of superhigh-rise buildings. From the prior art, various procedures and devices for surveys duringand after the phase of erection of a high-rise building are known. High-rise buildings aresubject to strong external tilt effects caused, for instance, by wind pressures, unilateralthermal effects by exposure to sunlight, and unilateral loads. Such effects are a particularchallenge in the phase of construction of a high-rise building, inasmuch as the high-rise

building under construction is also subject to tilt effects, and will at least temporarily loseits – as a rule exactly vertical – alignment. Yet construction should progress in such away that the building is aligned as planned, and particularly so in the vertical, whenreturning into an un-tilted basic state.

It is essential that a straight element be constructed that theoretically, even whenmoving around its design centre point due to varying loads, would have an exactlyvertical alignment when all bias ing conditions are neutralised. Because of differential raftsettlement, differential concrete shortening, and construction tolerances, this idealsituation will rarely be achieved.For this reason a regular matching of the reference system is required for surveys duringthe construction phase of a high-rise building once this has attained a certain height or a

certain ratio of height to cross section.Up to now, surveying on high-rise buildings is done by geodetic electro-opticaltotal stations yielding non-contact optical measurements of the points to be surveyed,these instruments periodically being referenced to fixed external reference points withknown coordinates. The precision of the entire surveying procedure depends on thereference points serving as fixed points for the total station; therefore, points are selectedfor which absolute constancy of the position is guaranteed. Primarily points close toground are suitable that are not subject to influences producing shifts. However,increasing construction heights, possibly aggravated by densely built-up surroundings,give rise to difficulties in the use of ground-level fixed points, inasmuch as the distance

between the tota l station installed on the uppermost construc tion level of the high-rise building and the reference points becomes excessive for exact referencing of the totalstation while the relative distances between the fixed points become too small,

particular ly so in heavily developed zones.Beyond a certain threshold height, it becomes altogether impossible to use ground-

level reference points. Particularly in the Far East, demand increases for high-rise buildings having heights beyond th is threshold and a rat io of height to cross section thatgives rise to strong tilt and sway of the building. The strong movements of the structurecreate a number of problems for the correct design of controls. It will be essential at any







Construction Sequence: Construction is progressing in a circular sequence on a 5 –7 day cycle for each level and this will cause the centre of mass of the building to

move from the vertical axis and may cause a corresponding movement in thestructure. Refer Figure 3. Building Design: The design of the building, with the set back on wings occurring

at different levels introduces a movement of the centre of mass in the building as itrises and the final position of the theoretical design shape is offset from the verticalaxis. This may cause a movement in the tower position which is closely linkedwith the construction sequence.

Concrete Creep and Shrinkage: Long term, differential, creep and shrinkage in thetower columns may cause the tower centre to move by small amounts over a long

period. The amount of deflection will depend on the level at w hich the differentialshortening develops.

Daily MovementsThis component may cause movement in the tower over a 24 hour period.

Solar Effects: The concrete surfaces exposed to the sun will expand whencompared to those on the opposite side of the building. This will result in the buildingmoving “away” from the sun. Mathematical modelling of solar effects on the structureindicate that with a temperature differential of ten degrees centigrade a movement of upto 150mm at the top of the concrete is possible over a six hour period. This equates to amovement of 25mm per hour at that level. Most of the control for the formwork needs to

be set during the day when the solar effect will be at a maximum.

Dynamic MovementsThese components cause movement in the tower with periods of as little as 10 seconds upto 15 minutes

Building Resonance: According to information from the structural engineers the building will have a natural period of 10 to 11 seconds in two axis which if the position data is computed at say every 0.5 seconds then the shape of a point plot of

30 minutes of data would resemble an irregular ellipse. If wind speed increasesthen the ‘size’ of this ellipse would also increase. Wind Drag: Wind loads will cause the building to move off centre by amounts

which are dependant on wind speed, direction and structural factors. Crane Loads: It is anticipated that the building will move to some extent when a

tower crane picks up or releases a load. These movements will be completelyrandom with periods of 5 to 15 minutes. When positioning surveys are beingcarried out it will be necessary to shut down the cranes to reduce the chances of arandom ‘bias’ in the measurement of the displacement. The loads and other effects





on the tower will cause it to move from the theoretical vertical axis and the natural building resonance will c ause it to oscillate about this offset position. The survey

system had to be designed to tolerate this movement and allow construction to proceed in a continuation of the alignment of the previous levels.

Form work SystemThe formwork for each concrete pour is comprised of a series of individual forms

which all require control. This has resulted in 240 control points for the formwork systemfor each level. It was not practical or safe to use the traditional method of plumbing upthrough floor penetrations and at the beginning of the project it was decided to useresection as the primary procedure for survey control.

Initial SurveysAt contract commencement six permanent bench marks were established around

the site and precisely surveyed. These marks consisted of a concrete encased steel “I” beam extend ing down to about 15m below ground level. A cap was cast at the top to provide a solid work platform. These marks were used for all the initial set out surveysand as a base for the monitoring work.

Lower LevelsDue to the large number of control points required for the formwork it was

necessary to develop a method so that the control was only measured once. The onlysolid part of the building is the concrete and the technique sets marks in the top surface ofthe newly cast concrete.

A total station instrument is also set up on the concrete and position established byresection to the external bench marks. The marks set in the top surface are measured byradiation from this resected control position and the precise coordinates for each markcalculated. When the formwork is raised to the next level the marks are offset onto themain working deck of the formwork which is tied in to the concrete at that position. The

back of the shutters can then be positioned from these marks. From ground to about Level20 resection was possible from the external control marks which were distant about 100to 150 m from the base of the tower. Observation redundancy was possible and very highquality results were achieved. Verticality observations confirmed that the tower was notmoving and raft foundation measurements indicated there was no differential settlementto cause the tower to tilt. Hence it was a straight forward surveying task to set out controlfor the formwork using this method.

Upper LevelsAs the building r ises it will come under the influence of various forces as described

in 1.2 above and will start to move by varying amounts and sometimes in random





directions. Above Level 20 it became increasingly difficult to sight the external controlon site due to obstruction from the upper decks of the formwork system. In Dubai the

nearest tall, stable, buildings were over 500m distant from the site and could not be used because of potential visibility problems and poor geometry.At this stage it became necessary to implement a new method of resection and a

measurement system that could tolerate building movement. It was also necessary toinstall a means of measuring the building movement to ultimately identify any long term,

permanent movement of the tower in a particular direction which might need to becounteracted.

CORE WALL SURVEY SYSTEMThe movement of the structure creates several problems for precise survey; at a

particular instant in t ime, theoretically, you need to know exactly how much the designcentre line of the building is offset from the vertical axis and at that same instant youneed to know the precise coordinates of the instrument. However a ‘mean’ position takenover a short period for both elements can provide a suitable solution.

Instrument Position DeterminationGPS operating in static mode are being used toestablish survey control at the upper levels. Thesystem comprises a minimum of 3 GPS antenna/

receivers mounted on tall f ixed poles at the toplevel of the formwork.A tiltable circular prism is placed below

each antenna and a Total Station instrument(TPS) is set up on the concrete visible to all GPSstations. The GPS plus TPS comprises a“measurement system”. In static GPS mode,satellite signal data is received and recorded for a

period of up to 1 hour. During this same period oftime, the TPS instrument is used to measure aseries of angles and distances to the prismsmounted below the GPS antennas. The TPS thenmeasures to the reference marks placed on freshconcrete which are the reference points forcontrol of the formwork as described in 1.4.1.After completion of observations, data is returnedto the office for processing. Computation of GPS





antenna positions is carried out, processed against data from a Continuous ly OperatingGPS Reference Station Leica GPS GRX1200 Pro with AT504 chokering antenna and

Leica GPS Spider software, using Leica Geo Office software (LGO).Computation of TPS position is then carried out actually as a least squaresresection. Finally transformation is performed of the 3 no WGS84 antenna coordinatesand resected TPS coordinates into the local coordinate system and from this adetermination of coordinates of all measured reference marks is made. These steps yieldcoordinates of survey instrumentation and reference marks in the site project coordinates.A total station, or more generally any theodolite, can be considered as a dual axis systemsupporting the line of sight of a transit/telescope. For reducing the effect of themechanical misalignments on the observations, classical operational procedures have

been applied since the first use of such instruments.Today, a total station can take these axis misalignments into account using an

inbuilt dual axis compensator and special firmware to correct the resulting error in themeasurements. However, the operational range of the compensators is restricted,typically to about six minutes of arc. The operator aligns the main axis coarsely bykeeping the bubble of the station inside the graduation. In case of a compensator “out ofrange” signal, the station must be realigned manually.

This procedure known by experienced operators as simply inappropriate whenoperating a total station in this case when we expect dynamic behaviour and overal as wethe building main axis will not be aligned with the direction of local gravity To remove

that restriction it will be necessary to consider this instrument as a local 3D axis system.The coordinates computed by using the observations (directions and distance) areinternally consistent but must be transformed into the reference frame defined by the setof GPS antennas. In our case as we use a single total station, the problem is simply a 3Dtransformation also known as similar ity transformation or Helmert transformation.





Building Alignment Determination

The Core Wall Survey System (CWSS) uses NIVEL200 dual-axis preciseclinometers to accurately determine displacement of the tower alignment from vertical.Clinometers measure absolute tilt to +/-0.2” arc. This angular measure can be applied tothe vertical distance of the clinometers sensor above the foundation raft to provide acomputed plan displacement in X and Y at that elevation due to the tilt of the structure.

A total of 8 precise clinometers are to be networked at approximately every 20floors up the tower as construction proceeds. Each instrument will be mounted in thecenter core wall in a boxout within the wall where casual disturbance is unlikely.

When the clinometers are installed initially they will be calibrated in relation to thesurvey control at that level by verticality observations from the raft foundation. A seriesof observations will provide a mean displacement in X and Y for that tilt meter at thattime and will then be applied to all future readings so that the output will reflect thedisplacement of the tower alignment at that level in relation to the vertical axis.Clinometers will be connected through an RS-485 single bus cable to the LAN port of adedicated PC located at the survey office running Leica GeoMoS software.

Continuous, real-time measurements of structure tilt can be logged for each instrumentfloor, and data output as X and Y components of building alignment from the vertical.Amplitude peaks of smoothed data represent structure oscillations.





The mean displacement of the regression line represents total mean displacementof the structure. A block of data corresponding to the GPS observation data will be used

for this purpose. Differentiation of the tiltmeter data at different heights will allowcorrection for nonlinear structure tilt.

Core Wall Survey SystemThe GPS Reference Station, the GPS receivers and antenna’s with circular prism,

the Total Station are combined with the precise clinometers network as shown belowcomposed the 4 measuring sub-elements of the complete data fusion system.

PRECISIONAn examination of the likely errors in the

CWSS indicates that it will be possible tocontinue to set out the formwork along thevertical alignment of the structure to a precisionof ± 15mm. It should also be possible to identifyany long term movement of the tower that has avalue of >20mm in any given direction.

ANALYSIS

Monitoring surveys will provideinformation on raft foundation settlement anddeformation and this can be used to accuratelydetermine the offset of the tower at a particularlevel due to the influence of these factors.Similarly surveys to measure the differentialshrinkage and creep in the core walls andcolumns can be used to derive this possiblecomponent of tower movement.

A dynamic model of the building has beendeveloped and from this it has been possible toderive values at any given level for the effects ofconstruction sequence, building design and solareffects. For the period of the control survey if thetower cranes are shut down then the onlyremaining unknown component of buildingmovement is that due to wind.

Weather stations are to be established atthree locations on the tower and these will stream





continuous data on temperature, wind speed and direction. This can be correlated with thetilt meter data to determine a relationship. It is anticipated that this analys is will reveal

any long term movements in a given direction and if necessary corrective action can betaken. The Nivel200 Network segment of this system can be used for tower monitoring, both during construction and after completion of the structure. If this is integrated w ithother monitoring information it will provide a complete system of structure monitoring.

A combination of GPS survey techniques, Automatic Total Station, clinometersreadings and mathematical modelling will provide a means to drive the construction ofthe world’s tallest building as a straight structural element and provided a wealth of dataon building movement. It’s only the start of a long journey up to the final completion ofthe Burj Dubai tower and the authors know that they will have to complement theexisting data fusion system with other elements the time being.

MATERIAL FOR HIGHRISE CO NSTRUCTIONS:

In building practice, materials have to be selected to meet specific functionalrequirement. The degree of protection, comfort and pleasure that a building of nay kind

provides throughout its working life depends on the materials that are used. Building

materials account for 70 to 75% of the total cost of construction.High rise structures are designed for static as well as dynamic loading. The constructionmaterials for high rise structures should have high strength under these loads. Thematerials should be light, so as to reduce the cost of foundation and overall costs as wellas be durable.

Some major materials of construction are considered below :

High grade materials1. Cement

The economics of concrete construction depends on the design of concrete mix,which in turn depends on the correct grade of cement and best combination ofingredients. Considering the relative costs of its constituents, the economic design aims atminimizing the cement content.

In construction of high-rise structures, concrete of high strength is required. Highergrade of concrete can be achieved either by using more quantity of cement in the mix or

by using high strength cement.





High cement content is costly, generates high heat of hydration and leads to morecracking and shrinkage. Hence, high grade cement (G43,G53) are effectively used to

produce high grade concrete.For the same cement content as that of G33, we can produce high strength concretewhich can be used to produce sleek and elegant structures. Alternately, by using lowercement quantity we can produce concrete of same strength. Since there is not muchdifference in the cost of G33 and G43/G53 cements, savings in cement is the directsaving in cost of construction.

Comparative studies carried out on concrete using G33 and higher grades ofcement show that the use of high strength cement results if following savings.

I. In the cost of cement 20-30%II. In the cost of steel 5-10%

III. In the cost of shuttering 5%High grade cements produce more durable(less permeable) concrete. High early

strength enables the shuttering to be removed earlier and thus speeds up construction.

2. ReinforcementIn RCC, reinforcement accounts for 30-40% of the total cost of construction per

m3 of concrete. Use of high grade steel substantially reduces this cost. For eg. In caseof doubly reinforced beam, use of Fe500 results in reinforcement savings of 44-47%

over mild steel (Fe250) and 14-15% over Fe415 in terms of weight and 35-37% overmild steel and 6-8% over Fe415 in terms of cost.

3. Advantages of using high grade materialsI. Sleeker and elegant structures, giving more flexibility in generating the

design concept.II. Earlier hardening and high ear ly strength speeds up the construction process.

Scaffolding can be removed in just 7-10 days instead of the usual 15-21 dayshence centring cost is considerably reduced.

III. Use of high grade cement to produce high grade concrete reduces the sectionand consumption of steel .

IV. Buildings can be designed with smaller sections to meet the same functionand to take the same load. This result in material saving and increase in theuseful carpet area.

V. As result of lesser cement consumption in concrete, G53 grade gives lowheat of hydration, giving crack free mortar and concrete.

VI. Saves cement consumption.Sr.no.

Item CementG43

CementG53

%Saving

%Saving





inMaterial

in Cost

Concrete1 Foundation 1:4:8 1:5:10 28.5 26.02 Footing 1:2:4 1:2.5:4.

513.8 10.8

3 Columns/slabs/beams

1:2:4 1:2.5:4.5

13.8 10.8

4 Water tanks 1:1.5:3 1:2:4 18.75 15.8Mortar1 Flooring

/Tilework

1:4 1:6 25 22

2 Br ickwork 1:6 1:8 33 203 Internal Plaster 1:6 1:8 21 18.54 External Plaster 1:4 1:6 30 275 Ceiling Plaster 1:4 1:6 25 22

Table (1) : Savings for various types of cement

Light Weight Concrete Normal concrete imposes heavy load on the structure, thus creating technical and

economical problems in design of foundations particularly in poor soils.Lightweight concrete reduces overall cost of the structure by considerably reducing thedead load. Saving in structural steel depends on the height of the building. In lightweightconcrete construction, since the dead load is reduced, the earth quake forces are reduced.Hence lightweight concrete buildings are better for earthquake prone zones.Since the dead load is considerably reduced, buildings can be built taller withoutexceeding the SBC of soil. When used in building f loors, it increases the ratio of LL/DLand permits wide spacing of columns, allowing more column free area.Light weight concrete increases thermal insulation and sound proofing. Use oflightweight concrete panels and structural members cuts down the energy consumption

on air conditioning and heating of rooms to an absolute minimum.

FlyashFlyash can be used in the form of ready mixed flash concrete, precast flyash

concrete building units (hollow or solid), clay flyash bricks, cellular concrete, sinteredflyash lightweight aggregate etc.Walling accounts for about 14% of the total cost in building. Hence saving in wall unitsto leads to certain economy. Clay flyash bricks are cheaper than clay burnt bricks, havethe same lifespan and are used for construction in Andhra Pradesh. Aerated lightweight





products lead to apprec iable economy in consumption of cement and steel due to theirlightweight and high strength to weight ratio. Aerated concrete products are ideally suited

for walling blocks.Flyash lightweight aggregate is suitable for use in produation of structural light weightconcrete and precast lightweight concrete buildings units.

1. Calcium silicate bricksProduction of calcium silicate bricks requires 30% less energy as compared to

traditional bricks. They reduce the cost of construction by around 40%. Less mortar isrequired as compared to conventional clay bricks. Lesser wall thickness are obtainedgiving more carpet area.

2. Cellular concrete blocksThey are lighter than clay bricks by around 40-45% and possess technical

advantages such as better strength to weight ratio, low thermal conductivity, better soundinsulation and resistance to fire and water seepage.There are appreciable savings in wall thickness and foundation cost. Plaster can becompletely avoided. From considerations of transportation, w ithin a radius of 40km fromthe plant site, cellular concrete blocks are cheaper by 10-15% are compared to traditional

bricks .Their density is almost one-fourth of concrete and one-third of bricks, leading to

reduced dead load and savings in cement and steel. They are easy to handle, transport andhoist, therefore are suitable in low bearing soils and in seismic zones.

3. Clay flyash aggregate concreteThese are lighter and easy to transport. Clay flyash bricks have low thermal

conductivity therefore have better insulation properties.

4. Sintered flyash aggregate concreteThis lead to a lower bulk density of concrete, resulting in a reduction of dead

weight of buildings by 30-40%. There is a corresponding reduc tion of 20-22% in the costof steel as well as the cost of steel as well as the cost of foundation.This concrete has better thermal and acoustical properties. It is more resistant to fire andearthquake hazards. It gives more living space for the same plinth. Precast units can bespeed up the construction process.

Polymer ConcretePolymer addictives such as powdered emulsions and water soluble polymers

produce a concrete of higher tensile and flexura l strength. It has much higher ductilityand elasticity. Polymer concrete is highly res istant to chemical attack, abrasion and





cavitation. Polymer concrete has good bond strength, low permeability and its hardensrapidly. Polymer impregnated concrete is used for precast wall panels. It enhances

durability of concrete and increases its strength by as much as five times.

FerrocementPrecast units ferrocement produce light and thin structures, resulting in

considerable savings in formwork and costs. Ferrocement encased RCC columns werecast and tested for direct compression ta the Government college of Engineering Pune.These columns carried same load as RCC columns and saved the cost of formwork. Theferrocement casing acted as inbuilt formwork.A ground plus one structure has been constructed using only ferrocement precast chajjas,doors, walling units, staircase are widely used in Pune for various constructions.

Insulating MaterialFibreboards and gypsum plaster boards are light and fire resistant. These are

available in various dimensions. In particular they are used for false ceilings, lightweight partitions and insulation walls. Phenotherm and decofoam are fire resistant insulat ionforms. They have exceptionally low thermal conductivity and low water absorption.

Wonder wood

This precast concrete with wood like grains is used for frames for doors andwindows. It is highly economical compared to wood, steel aluminium, FRP or any othercomparable material used for frames. These high strength and load bearing memberseliminate the need for casting lintel.

Precast UnitsPrecast units eliminate costly shuttering. Furthermore, since the units are made

under factory conditions, there is greater quality control. Hence, uniform units of highquality and strength can be obtained.

Precast units require less labour and can be erected faster. Therefore, constructioncan be speeded up. Shrinkage cracks are eliminated, which avoids the corrosion ofreinforcement and makes the structure more durable. Precast unit construction isstatically determinate. Therefore standardised sections are used.Hollow blocks are light, economical and easy to handle. They have better appearance,

better insulating properties and require lesser maintenance. The can be made in varioussizes and shapes.

Siporex Blocks







location of the insulation protec ts the primary structure from temperature extremesand moisture-related damage,

exterior insulation, particularly in steel framed buildings, can result in energysavings, and reduced cost of HVAC equipment,

complex surface features are possible in a wide range of finish colours andtextures,

smaller dead loads and reduced structural costs, thinner walls will increase usable area and reduce building footprint, an EIFS can be pre-manufactured in tranferrable panels.

Disadvantages include:

sensitivity to deficiencies in workmanship, particularly at joints penetrations andsealants, susceptibility to mechanical damage.

Consideration should also be given to three key elements of EIFS: Rain Penetration at Joints Interstitial Condensation Cracking of the Lamina

DESI GN CONSIDERATIONSThe most serious and widespread problems associated with EIFS relate to moisturedamage, often to the substrate system or sheathing since EIFS themselves are made up ofessentially moisture tolerant materials.

Rain Penetration at Joints Face sealed joints are not recommended; use 2-s tage seals in joints that provide for

water drainage at the source. A drained subsill under windows is essential in most applications. The EIFS finish should stop at least 8” above grade & a special system is required

below grade. Manufactuers should be consulted for the appropriate details.

Interstitial Condensation Where possible, additional insulation should not be placed in the stud space. This

will maintain the interior side surface temperature of the substrate sheathing abovethe dew point of the interior air. If insulation is required in the stud space adynamic analysis for the prediction of condensation should be carried out prior tofinalizing the design.





A vapour barrier is required in EIFS clad walls. A membrane or trowel appliedvapour barrier can be used between the insulation board and the sheathing.

Alternatively, a separate vapour barrier on the inside of the wall can be provided.

Cracking of the LaminaCracking caused by excessive stresses can occur as a result of inappropriate

location of joints between insulation boards, or insufficient or inappropriate control andmovement joint spacing and location.

EIFS with thin glass-mesh reinforced high polymer content laminas mayexperience durability and performance problems if the mesh is not properly embedded ina base coat of the proper thickness. The base coat provides the primary water penetrationresistance, and when reinforced, the majority of the structural properties of the lamina.

PRESSURE EQUALI ZED RAINSCREEN (PER)

THE ISSUES

Rainscreen walls are assemblies that provide a cavity behind the exterior cladding.The principal function of the cladding is to deflect intruding rainwater without damage to

moisture sensitive materials within the wall assembly. However, water that is present onthe outer face of the cladding, may enter the cavity as a result of a number of forces,including momentum, surface tension, gravity and air pressure differences. The cavityacts as a capillary break to prevent water reaching the remainder of the wall assembly.The cavity also acts as a drainage space to shed moisture to the exterior by means offlashings and vents provided at the bottom of each cavity compartment.

Pressure equalized rainscreen (PER) wall assemblies attempt to reduce water penetration of the wall assembly as a result of pressure differences. Wind forces create inhigher air pressures on the exterior of the wall than within the building or the wallassembly. Air movement in response to this pressure difference can transport moisture

present on the exterior of the cladding into the wall.PER wall systems and assemblies require that they be designed so that the pressure

difference across the exterior cladding is nearly zero at all times. This reduces the drivingforce associated with pressure differences, and prevents moisture from moving throughthe wall assembly. The air barrier, in conjunction with a vented and compartmentedcavity, acts to reduce or eliminate air pressure differences across the cladding.

The control of airflow is inherent in the PER wall systems and assemblies. If theairflow through and within the fabric of the wall is not controlled, the air pressuredifference across the rainscreen (or outer section of the wall) cannot be equalized.





Even with the best design concept andconstruction practices, however, there is always the

possibility that some water will f ind a way inside thewall cavity. Therefore, the wall system also has tocontain features that will drain this water to theoutside. As in a rainscreen assembly, any incidentalwater which may enter the cavity is drained to theoutside by means of the cavity and flashings.

At any time, the air pressure loading on wallsvaries significantly from one location to another. Aswind loads change, positive pressures are created onsome areas of the building envelope and negative

pressures on others. It is necessary to divide, orcompartment, the cavity into smaller areas. In thisway, the range of pressure differences acting on eachcompartment can be significantly reduced.

The design parameters for PER wall systemsare still in development. Considerable researchinformation on this subject, however, is nowavailable from a number of Canadian organizations.Rainscreen walls require certain design features in

order to achieve pressure equalization under dynamicwind conditions. To obtain pressure equalizationacross the rainscreen, the airflow through the wallsystem and the lateral air flow within the wall cavitymust be controlled.

The design of the wall system must include:• Air Barrier Systems• Sealed Compartments• Appropriate Venting• Quality Control

DESIGN CONSIDERATIONS

Air Barrier SystemsThe importance of the air barrier system to effective building envelope

performance has been discussed earlier in this section. Air barriers are particular lyimportant in pressure equalized rainscreen wall assemblies.





The wall system must contain a continuous and durable air barrier that controlsairflow through the wall. The air barrier system must be made of structural elements, or

be supported by structural elements capable of resisting wind loads. The air barriersystem should be rigid to minimize material fatigue, especially at the points of attachmentto the structure.

Sealed CompartmentsAir pressures induced by winds vary over the width and height of the building.

Steep gradients can develop towards the corners and the roof line while pressures can befairly uniform near the centre of the walls. These pressure differentials can induce lateralairflow within the cavity unless interrupted at suitable intervals by sealed compartments.The frequency of these cavity compartments should be such that the air pressure withinany compartment can be nearly instantaneously equalized with the exterior pressure.

The size of the compartments should vary over the face of the wall, with largercompartments located at the centre where pressures gradients are lower, and relativelysmaller compartments located at higher pressure gradients locations near the buildingedges. Cavities must be closed at the corners because wind flowing around the building

produces high pressure differences at these locations. Specific design guidelines include: the cavity depth should be at least 25mm, the cavity should contain sealed compartments at each corner and at 1.2m intervals

for 6m from the corners and the top,

sealed compartments located at the centre of the wall in both directions at every3m to 6m.

VentingSufficient venting is required in the pressure equalized rainscreen to ensure that

cavity air pressure is quickly equalized to the outside pressure. The location and size ofvents must allow air to flow into and out of the cavity, thereby achieving pressureequalization across the rainscreen. The effective area and location of the vents should be

based on the envelope a ir leakage and the cavity volume.





The stiffness of the outer wall layer and air barrier system will affect the volume of the

cavity and must be taken into account whendesigning the venting requirements.

Venting must also be provided at locationsthat will facilitate drainage of the cavity.

Vent holes should be at least 10mm indiameter to prevent blockage.

To obtain pressure equalization of therainscreen, a rule of thumb is the ventingarea should be 25 to 40 times larger thanthe leakage area.

Care must be taken in masonryconstruction to ensure that vents are not

blocked by mortar.

Asymmetrical VentingAppropriate sizing and location of vents

can provide an additional means of improvingrain penetration resistance. The asymmetricalventing concept is based on concentrating ventsin places where the wind pressure on the face ofcompartment is greatest. This has the effect ofraising cavity pressure so that most of thecompartment experiences an outward pressure.The raised cavity pressure forces water out ofleakage paths rather than in. Asymmetrical

venting is achieved by concentrating the requiredvent area on the side of the compartment closestto the centre of the façade.

Quality ContolThe quality control and commissioning process has been discussed previously in

the Air Barriers section. A similar process should be applied to other envelope systemsincluding pressure equalized rainscreens.

The commissioning of a rainscreen wall will verify building performanceobjectives before completion of construction. This is accomplished through performance





engineering and field or laboratory testing. To assist with performance engineering,CMHC has developed a computer program (RAIN) that simulates the pressure

equalization (P.E.) performance of any design.The quality control process for pressure equalized rainscreen walls should include: determining that facade areas and windows to be designed as pressure equalized

rainscreens, locating vertical and horizontal compartments and determining the number of

rainscreen cavities, developing basic design of wall or window system to include an air barrier

system, compartment seals, and cladding system with vents/drains,

determining physical attributes to each rainscreen cavity i.e. volume, vent area,leakage area, and stiffness of cladding and air barrier systems, simulating the performance of each rainscreen cavity using CMHC’s “RAIN”

Rainscreen 2.1 and iterate the design until performance attributes are attained (90% pressure equalizat ion),

constructing a mock-up to test the P.E. performance of a design at pre-construction,

assessing the complete design of envelope and preparing constructiondocumentation,

preparing a tender package requ iring on-s ite mock-up test to verify field performance and workmanship quality,

complete testing of rainscreen wall and window system, correct problems asrequired, and report results,

ensuring rainscreen P.E. performance complies with design objectives andcertifying that workmanship as complies with drawing and specifications,

providing design informat ion necessary for proper maintenance of wallssystems

RETROFI T OPPORTUNI TYPERs should be used in all high-rise retrofit or recladding projects. In addition to

providing an appropriate level of water management performance, rainscreen assembliesalso include an effective air barrier and offer an opportunity to add additional insulationto the exterior of the building. Changing from face-sealed walls to raiscreen assembliesmay result in additional wall thickness. Careful detailing will be required at interfaceswith components such as windows and other penetrations. In many older buildingsreplacing windows at the same time as recladding will allow for correct detailing of







despite the reduction in scale. For this reason, these studies can only be carried out byhighly specialized test institutes.

5.5.1.1 CONSTRUCTION LIC ENSI NG PROCEDURE

The construction licensing procedure is normally specified in theconstruction laws of the country concerned. As a rule, the principal will file anapplication with all the requis ite documents (description, plans, analyses, etc .) to therelevant construction supervisory authority. The involvement of specialists is obligatoryin the case of larger and more complicated projects, such as those involving high rise

buildings. Such specialists include experts from the municipal f ire brigade, waterauthorities, trade supervisory offices, environment protection agencies or similar officesin other specific fields. These specialists review the applications for a constructionlicence and specify any additional requirements to be met. The licence is then sent to the

principal together with the requirements specified by the specialists; responsibility forcomplying with these requirements rests with the principal or owner of the building.

5.5.1.2 OTHER CONSTRAINTS

Even in our high-tech era, the planning and construction of a high-rise building are not dictated only by naked fac tual constraints. Tradition, religion and eventhe belief in spirits and demons still play a not insignificant part in many countries.Take, for example, the Hong Kong and Shanghai Bank building in Hong Kong: duringthe planning phase, a geomancer or expert on “fung shui” (i.e. “wind and water“)repositioned the escalators and moved executive offices and conference rooms to theother side of the building on the bas is of astrological investigations and measurements inorder to guarantee an optimum sense of well-being for clients and employees. However,it must be said that such intervention is limited by technical and structural requirements.In western countries, too, the owners are guided by similar considerations when the 13thfloor is omitted from the planning or the technical installations are deliberately located onthis floor in order to avoid the unlucky number 13.

5.5.1.3 CONSTRUCTION PRACTICE







phase, but also during the subsequent construction phase, errors may possibly not bediscovered until the work has reached a fairly advanced stage.

This leads to time-consuming and costly changes and corrections, usually atthe expense of the professional indemnity insurance prescribed for architects in manycountries. The most commonly occurring design errors can be subdivided into twogroups: failure to observe building and planning codes on the one hand, and errors in thechoice of materials and wrong or inadequate construction details on the other.

5.5.1.5 FAILURE TO OBSERVE BUILDI NG AND PLANNING CODES

It may be assumed that, in the majority of countries, when a buildingexceeds a certain size – and this will certainly apply to high-rise buildings –corresponding plans must be submitted to the construction licensing and supervisoryauthorities for inspection. The inspection and approval procedure not only encompassesaspects under the building code, such as compliance with specified distances and thespecified height and size of a building or its type of use, but also the safety of the peopleinside the building. Such aspects include compliance with fire protection requirements inthe building, the position and number of escape routes and the number, location andexecution of stairwells and traffic areas. Even such seemingly less important aspects ascompliance with acc ident prevention regulations are reviewed, for instance as regards the

height of railings or the distance between bars in railings and grids.In many cases, however, the design is changed at short notice during theconstruction phase, with the result that the plans submitted for inspection no longerreflect the actual situation. If errors are made by the designer at this stage in violation of

building and planning codes, they will only be discovered (if at all) during f inalinspection of the building by the construction supervisory authority as specified in manycountries. Such changes frequently cannot be undone, and this forces both sides to acceptcompromises possibly at the expense of the building’s safety.

Despite the numerous statutory instruments and court rulings in test cases,the complex legal relationship between principal and architect makes it necessary for thecourts to decide who is to bear the costs incurred as a result of such errors. In most cases,

both the architect’s legal protection insurer and his professional indemnity insurer will beinvolved. If the errors are not discovered and the building is taken into service, however,this may not only increase the probability of a loss occurring, but also pose an acute riskto life and limb for its users. Particularly grave defects only become evident when theloss actually occurs, for instance when a fire occurs.

Fire insurers, personal accident, health and life insurers, and occupationaldisability insurers and once again the liability insurers may all be called upon to bear thecosts once the courts have settled the question of blame. If a guilty party can be





identified, that party can face considerable penalties for any shortcomings ascertained. Itis irrelevant in this context whether this party was actually aware of these shortcomings

or merely must have been aware of them. For this reason, all insurers – and particularlyfire insurers – are well advised to ascertain whether all of the safety requirements have been met before they conclude a policy for buildings entailing high risk potential.

4.4.3.13. MATERIALS A ND CONSTRUCTION DETAILS

Not only the legal re lationship between principal and architect isexceedingly complex; just as complicatedis that between architect and (sub)contractors and particularly among the(sub) contractors themselves. Although thearchitect or specialist engineer specifieswhich materials are to be used or installed,the (sub) contractor must check whether

these materials are indeed suitable for suchuse. Modern and unconventionalconstruction practices frequently make itdifficult or even impossible for (sub)contractors to determine whether thespecified materials or the executionintended by the designer are indeed

suitable and correct.Unsuitable materials and connections in sanitary installations, for instance,

can rapidly result in water damage due to burst pipes. Unsuitable insulating materials cangive off toxic gases or acids in the event of a fire; incorrectly dimensioned fixtures forsuspended ceilings or facade elements can cause bodily injury or property damage if theyfall down. In extremely simplified terms, it could be said that most of the damageincurred in or on a building is ultimately attributable to design errors.

4.4.3.14 PRECAUTIONS DURING CONSTRUCTION





The loss potential during construction is an aspect which cannot beneglected. Although the stability of the building during the various construction phases is

documented by corresponding structural analyses, such equipment items as facadeelements or temporary structures are usually not taken into account, or only inadequately.Addit ional precautions must therefore be taken during the construction work, particularlyif the contractor is given sufficient advance warning of an impending windstorm. A lossof more than DM 5m was incurred during construction of a 90-storey high-rise buildingin the Far East. Subcontractors had temporarily stored such electrical installation materialas control cabinets and relays on the upper floors of the building shell, but delivery

bottlenecks led to a delay in assembly of the facade elements on these floors. Aconsiderable proportion of the electrical material stored on these floors was soaked byTyphoon Herb as it passed over in 1996 and consequently exposed to the risk ofcorrosion. Since the damage w as foreseeable and precautionary measures were not taken,the insurer was only obliged to indemnify part of the loss under the policy.

4.4.3.15 Other Risks

For the sake of completeness, mention must also be made of a few otherrisks which, although closely associated with high-rise buildings, either occur very rarely,such as terrorism, are unavoidable, such as wear, or are often underestimated, such as theconsequential costs due to physical damage.

High-rise buildings with their characteristic silhouette in a city’s skyline notonly represent a magnet for tenants, customers and guests, but unfortunately also becomea popular, sometimes inadvertent, target for terrorist attacks, as the 1998 bombing attacksin Nairobi and Dares Salaam show. A skyscraper’s famous name is enough to assure theterrorists of the desired media attention following an attack. In many cases, however, thedominant presence of a high rise building will suffice to obstruct the devastating shockwaves of an explosion somewhere else.

4.5 CULTURAL RESPONSE

The skyscrapers are built for only two reasons:” to make money, respondingto existing demand, or to advertise and flaunt the money one already has” Said Philip

Nobel11. Nowadays we can rarely tell the location of a h igh rise structure due to theirsimilar style. Some architects even feel proud that their work can be located anywhere inthe world. Obviously, tall building is not a typology to fix in with its context. It prefers tosoar above, and dominate its surroundings. But that does not mean it cannot become a

positive element in the urban composition. It can and should relate to its surroundingsand respond to the history cultural context. Antony Wood in his “New Paradigms in High





Rise Design” (2004) introduced several approaches to design help cities in their quest foran appropriate high rise expression.

4.6 ENVIRONMENTAL ASPECTS

Concerns for the susceptibility of our environment are increasing. Thedeterioration of the ozone layer and air quality in urban areas, the depletion of fresh watersupplies and the degradation of water courses, and the loss of natural habitats allrepresent societal problems that need to be addressed. Residential development has amajor impact on the environment at both local and global scales.

A new building can destroy local natural ecosystems, and can impact negatively onadjacent development. Both the construction and operation of residential buildingsconsume vast quantities of energy, materials, water, and land. The waste emissions and

pollution associated with buildings are also significant. In order to sustain the quality ofthe environment and healthy lifestyles, it is crucial that residential development useresources more effectively and more efficiently, while preserving the integrity of thelocal ecosystem.

In response to these needs, the design and construction industry has begun to make

advances. In most cases, environmentally responsive design will not significantlyincrease design or construction costs. For example, orienting a building to optimise solargains, or specifying low flow water fixtures, can result in operating cost savings. At thesame time, there are many precedents of residential developments where anenvironmentally responsive design approach resulted in greatly reduced infrastructurecosts. Indeed, when a lifecycle assessment approach is used, the benefits of ‘green’design far outweigh the costs.

The following section provides an overview of possible approaches for enhancing theenvironmental performance of high-rise buildings. It discusses this issue from the pointof view of local ecological impacts, resource use and attendant waste emissions, andindoor occupant health.

The primary design concern for many tall buildings is their operational efficiencyrather than their environmental impact. A new balance needs to be struck between thesetwo factors.

4.6.1 Site Selection and Clearing







The site plan should be premised upon preserving, protecting, and enhancing suchnatural features as site contours, stream channels, hydrological flows, existing vegetation,

scenic views, and wildlife habitats. These features all play integral roles in the properfunctioning of the ecosystem as a whole, and can contribute significantly to proper building functioning. Restrictions on development of environmentally sensitive orimportant productive lands are crucial. Agricultural, forest renewal and hazardous lands,or lands that might result in extensive environmental damage, should have limiteddevelopment. For example, steep slopes and hillsides, flood plains, and wetlands are allexamples of areas where development should be restricted and / or regulated.

Building Location and FootprintThe construction of high-rise buildings can affect the local microclimate,

modifying wind and sun patterns in the area, and shading other buildings and ecosystems.The building should be s ited to create des irable summer and winter microclimates at the

pedestrian level. The location of a building on a site can result in posit ive or negativeenvironmental impacts. Consideration should be given to the impact of the building onviews, how much of the site will be disturbed both during construction and operation, soilcapabilities, linkages to transportation networks, existing buildings on site, changes to themicroclimate caused by altering the contours of the land, and so on.

In order to minimise site disturbance for construction, buildings and access roads

can be aligned to follow the length of existing contours. The building’s impact upon localsolar access is an important consideration. Buildings should be located to minimise theloss of solar access to surrounding buildings and publicly accessible, open space areas.This is an important consideration for colder climates in particular.

Ideally, high-density development should have good access to services andamenities, maximising the potential for pedestrian travel and minimising the need for theautomobile. Easy access to public transit, stores, health services, schools, and recreationalfacilities all provide for a more sustainable approach to development. Opportunities formixed uses at the lower levels of the building can reduce infrastructure costs and providefor a livelier community aspect in the building. Examples of mixed uses include daycarespace for children and the elderly, as well as the more typical small-scale retail,

professional and commercial facilit ies.

Design of site features such as outdoor sitting areas, playgrounds and allotment gardens provide an opportunity for building residents to enjoy the outdoors and socialise around acommon interest.

There are many other opportunities to enhance the relationship of the building tothe neighbourhood. These include orienting the building to pedestrian traffic, massing





and siting the building to relate to the scale of surrounding structures, providing anentrance design that is pedestrian friendly, and minimising the use of large quantities of

pavement.

Building OrientationA building’s orientation has enormous impacts

on the ability to optimize all opportunities forenvironmentally-responsive design strategies. Forexample, natural daylighting, heating, and ventilationstrategies are all linked to the building’s properorientation. A site’s latitude determines the sun’sazimuth at any given time of day and year. Simplecalculations will determine the path of the sun and a

building’s orientat ion should be determined to takeadvantage of this information. The effectiveness of

pass ive and active solar systems w ill be enhanced withappropriate building orientation and maximum accessto sunlight (SSE to SSW 5% to 15%).

Consideration should be given to the minimisation of solar shadows. Thecalculation of site shading can avoid the creation of on-site solar voids and cold-air

drainage dams that collect pools of cold air. The shading of adjacent buildings and lotsshould also be avoided. This is particularly important in temperate and cold climates. The building should be orientated to consider existing airf low patterns and their cooling effectin both summer and winter. Consideration should also be given to the building’s effectupon local wind patterns and snow accumulation, avoiding adverse effects upon adjacent

buildings or public open spaces.A building should also be oriented so as to maximize the safety, ease of access and

protection from the elements of its entranceway. The use of overhead structures nearentranceways, for example, can provide pedestrian protection from cold downdrafts.

RETROFI T OPPORTUNI TI ESWhile there are few changes that can be made to a building’s location or

orientation through retrofits, there do exist some opportunities for improving theenvironmental performance of a building through site alterations.

At the site level, the most readily available and least costly opportunities arethrough modifications to the surrounding microclimate. In many cases, such retrofits canimprove the energy performance of the building at the same time as improving therelationship of the building to its natural context. For example, altering paving materials





(from asphalt to pervious pavers) can lead to reductions in surrounding micro-climatetemperatures that in turn reduce the cooling loads on the building while also addressing

storm water run-off issues.

Another example is to add landscaping interventions that enhance the naturalfeatures of the site while also improving the building’s energy performance. These caninclude such things as adding deciduous plants on the south and west sides of a buildingto allow for summer cooling and winter solar access.

4.6.2 Shadow cast and Wind impact

Tall buildings in an urban context cansuffer from more problems with over shading and rightsto light, can cause or be the cause of glare, and cancreate wind tunnels. However it should be possible toovercome all of these issues through good design. Whilean individual high rise can be ideally suited to capturingthe heat and light energy of the sun, a second or a thirdtower constructed in its shadow would be adverselyaffected. As clusters of tall buildings are contemplated

and solar analys is of these clusters can optimize thelocation and orientation of towers, both of which arecrucial to their sustainable deve lopment.

The wind funnelling effect of clusters of buildings will impact on the planning and arrangement of future developments if they are to be sustainable. Designersand researchers are exploring opportunities for harnessing wind power from tall

buildings. Wind speed increases with height, and new tall buildings have the potential toreduce the consumption of fossil fuels by generating electricity with wind turbines.Funnelling effects from the profile and orientation of a tower or group of towers can beused to gain the optimum electricity generating capacity. As Ken Yeang (2002) indicatedin his book wind can be utilized as a free tool available to the designer and occupantrather than being shut out of the building. Natural air conditioning can be achieved byallowing air in and through the internal spaces of the building, as appropriate. As well as

being energy efficient, fresh air can c reate a healthier interna l environment and ra ise thecomfort level of occupants. Building occupants get the opportunity to regulate fresh aircoming into the building, helping them to adjust the airflow as required.

Standards





Reduce the shading and glare impact on surroundings

MATERIALS SELECTION

THE ISSUESThe materials used for the construction, operation, maintenance and renovation of

buildings represent enormous quantit ies of resources. As well, the extraction,transformation, use and disposal of raw materials cause equally significant impacts on theenvironment. Habitat destruction, resource depletion, air pollution, and solid wasterepresent some of the environmental costs associated with the flow of constructionmaterials. For this reason, design professionals now often inc lude environmentalconsiderations into the materials selection process. In particular, life-cycle assessment /analysis of construction materials and design guidelines that specify the use of ‘green’materials are available.

The key considerations involved in the selection of materials include: Source / quality of materials Embodied energy Quantities of materials Impact on occupant health Impact on natural ecosystems

Materials selection guidelines

DESI GN CONSIDERATIONSSource / Quality of Materials

Many materials come from sources which are considered non-renewable or whichinvolve more severe negative environmental impacts than others. Tropical hardwoods areconsidered a scarce resource, not just because they represent an endangered species, butalso because the acquisition process causes dire ramifications on biodiversity. Theselection of materials should involve consideration of the source in order to ensure that anon-renewable material is not being used. For wood products, third-party forestcertification is the best way to guarantee the suitability of the source.

The source of materials also refers to whether materials are virgin or whether theyare salvaged. Using salvaged materials and materials with recycled content reduces theextraction of raw resources. Assemblies that allow easy extraction of the material forrecycling when the building is eventually replaced also result in reduced environmentalimpact.





It is also necessary to consider the quality of the materials. Lower quality, lessdurable materials will require frequent replacement—meaning that more resources will

be used without adding any value to the building. While lower quality materials may costless at the building’s inception, both the economic and environmental cost will be muchhigher over the lifetime of the building. Durable materials with a long service lifetypically are those that are low-maintenance and that result in lower operation costs. Hardflooring, for example, has several times the service life of vinyl flooring or carpets, andreduces both waste and c leaning requirements.

Em bodied EnergyEmbodied energy is the term used to describe the energy input invested in a

material during extraction, manufacturing, transportation, and installation. Throughchoice of materials, the designer can greatly influence the embodied energy invested inthe building as well as the energy required to operate the facility. The goal is not tominimize embodied energy per se, but to consider its significant contribution to total life-cycle energy associated with the building. As a case in point, processing of recycledaluminium requires only 5% of the energy necessary to produce aluminium from bauxite.Because only 7% to 10% of the embodied energy in buildings is the result of the on-siteconstruction process, it is crucial to expand embodied energy calculations to include theentire life-cycle of the building and its attendant material requirements. For example, ifthe construction of a new building involves the demolition of an existing on-site building,

the initial embodied energy calculations should include materials removed throughdemolition.Reducing the embodied energy of a building can be achieved through:

Increasing the useful life of buildings and their components, Reducing the energy intensity of building materials (such as f ly-ash substitution in

concrete), Reducing the amount of material in a building, Reducing construction waste, Using advanced framing techniques, Increasing the amount of recycled material in a building, Using more durable materials, Using local rather than imported products.

Quantities of MaterialsVery large quantities of materials are used to construct and maintain buildings. The

failure to optimize designs results in an excessive amount of materials being used.Opportunities exist to eliminate oversized and decorative materials and still achieve











In 1998, an estimated 4.6 milliontonnes of solid waste was generated from

construction and demolition sources inCanada. This total represents 157 kilogramsfor each Canadian. The generation of solidwaste results in pressure on landfill space, andthe contamination of soils and water. It canalso indicate that a material object has beenremoved from the productive cycle well

before the end of its useful life.In terms of residential buildings, solid wasteis created during both the construction andoperation of the building. Researchersestimate that for every $1 billion spent onconstruction, 40,000 tonnes of waste are produced. Currently, 16% of the total volume ofCanada’s landfills can be attributed to residential construction waste.

The amount of solid waste generatedfrom day today operations varies, but isequally significant. For these reasons, it iscrucial that the generation of solid waste

during construction and daily operations bereduced. Along with these environmentalissues, rising disposal costs and bans ondisposal of some construction materialsrequire that the construction industryintegrates waste management planning into its

projects.

Key considerations to address with respect to solid waste include: Building construction Building operation Building demolition Waste management plans

DESI GN CONSIDERATIONSBuilding Construction

Construction waste makes up a significant proportion of the total waste stream:residential construction wastes are estimated to represent approximately 16% of wastestaken to landfill.1 As much as 1 1/4 tonnes of new products brought to the site are wasted





in the construction of an average house. Both the economic and environmental costs ofdisposing of this waste are enormous. However, construction waste can be cut by as

much as 85%, and disposal costs significantly reduced by implementing plans which are based on the 4 R’s of waste management.

Building OperationThe solid waste that is generated during the operation of res idential buildings is

typically comprised of consumer products and organic waste from food preparation andlandscaping. About half of the solid waste stream from residences consists of packagingmaterials; approximately 30% of organic materials, and the remaining 20% is made up ofother paper products, textiles and small amounts of old appliances and householdhazardous products. Through recycling and composting strategies, up to 80% of thiswaste stream could be reduced.

If appropriate dedicated facilities for composting and for recycling storage /handling / pickup are integrated into a building’s design, residents will have theopportunity to achieve such reductions.

Building DemolitionThe waste caused by demolition represents one of the largest contributors to the

waste stream. The economic costs associated with disposing of this waste are alsosignificant. It is estimated that approximately five to eight percent of the total job costsare allocated to disposal. By managing demolition responsibly, however, significantquantities of demolition waste can be diverted from disposal. Case studies have shownthat up to 90% of waste generated in demolition can be diverted cost-effectively. Throughdismantling rather than demolishing a building, for example, such savings can beachieved from both cost and environmental perspectives.





Waste Management Plans

Establishing waste management plans can reduce the costs associated withdisposal, and can improve demolition and construction practices. Waste management plans are based on reviewing, reducing, reusing and recycling.

Review Perform a waste audit, tracking amount and type of average construction waste, Review conventional practices which contribute to excessive waste generation and

develop a lternative procedures, Identify disposal costs and restrictions.

Reduce Implement purchasing options that minimize packaging and product waste (i.e.

bulk purchase of sealants, reusable packaging containers , no packaging left on site by suppliers, etc.),

Avoid damage and deterioration of construction materials by proper on-sitehandling practices,

Select equipment and materials which allow for repair of parts and componentsrather than requiring replacement.

Reuse Conduct pre-project waste inventory to optimize re-use opportunities, Retain existing buildings or materials, Reuse materials on site (i.e. crushed masonry for driveway fill, drywall scraps in

interior partitions, etc.), Sell or give away demolition materials.

Recycle Identify markets for recycle materials, Separate materials on site as they are produced for recycling purposes, Use recycled content and recyclable construction materials where possible.

RETROFI T OPPORTUNI TI ESThe focus of retrofit opportunities in terms of solid waste is on ensuring the most

appropriate facilities for collecting, storing and handling waste for recycling andcomposting. Although the best opportunities for providing dedicated waste managementspaces exist during init ial design and construction, the conversion of interior and exterior





spaces to perform waste handling functions is possible. While it is unlikely that a building will be retrofitted with recycling collection chutes or shafts, it is possible that

spaces can be modified to permit the separation, collection and storage of materials forrecycling and / or composting. These spaces should be large enough to accommodate asignificant diversion rate, and should be easily accessible to occupants and to custodialstaff.

WATER

THE ISSUESIncreasing residential demand for water is placing significant pressure on water

supply, delivery, and treatment infrastructure. It is an issue that results not only innegative environmental impact, but that also is significant from health and economic

perspectives. From a resource point of view, the issue is one of declining supplies, asmanifested in lower lake, river, groundwater and aquifer levels. From an ecological pointof view, it is an issue of degraded fish and riparian habitats. From a health point of view,it is an issue of declining water quality. From an economic point of view, it is an issue ofthe need for municipalities to keep pace with the required costs for upgrading andreplacing infrastructure.

The key considerations included in water consumption and conservation includes:

Domestic indoor water uses (toilet flushing, bathing, washing cleaning anddrinking) HVAC components (cooling towers) External water use On-site water treatment Storm water retention

HVAC SystemsThe principal water use associated with HVAC components in a high-rise building

relates to evaporative losses from cooling towers. It should be possible to reduceevaporative losses to less than 5% through better design. Opportunities to reuse w ater formake-up purposes should be explored, rather than using potable supplies.

Exterior Water UseOutdoor water consumption is a major concern to water authorities. Peak monthly

demand for water occurs during late summer when municipal reservoirs are at theirlowest levels. Most municipalities that impose watering restrictions do so during summermonths when outdoor water use substantially increases overall consumption. There are





many conservation practices that can reduce outdoor water consumption. Some of themost common approaches are discussed later in this section, in Landscape Practices.

On-Site Water TreatmentCentralised wastewater treatment is the status quo for most municipalities. These

sewage collection and treatment networks represent extensive infrastructure with largeenergy requirements. Canadian municipalities use substantial amounts of energy in theoperation of water and wastewater treatment facilities. The total amount of energy used isapproximate ly equal to the energy required to operate all munic ipally-ow ned buildingsand facilities.

Of the total energy required for these operations, wastewater treatment plantsaccount for approximately half, or 2200 GWh per year. Municipalities use waterconservation policies to reduce peak water demand, defer the upgrading of facilities andto ensure adequate supplies of water. These also have the additional benefit of reducingenergy consumption at water and wastewater plants.

One strategy to reduce water consumption is to use on-site infrastructure to treatwastewater and reuse it for non-consumptive purposes. On-site treatment systems offeran alternative to the conventional centralised approach. Essentially the on-site systems

provide a modularised and low cost system for treatment in close proximity to the

buildings. The on-site systems can be built incrementally, which reduces the need forlarge capital expenditures. Moreover, since key components of the infrastructure may belocated within each private development, municipal expenditures can be further reduced.

On-site operations provide primary and secondary treatment that produces waterthat is colourless, odourless and suitable for many re-uses within the vicinity. Also, thetreatment facility can be designed for multipurpose use, giving added value to nearbyresidents. For example, a secondary function of a solar aquatic liquid waste treatmentsystem is a greenhouse.

Exterior Water UseFor the typical high-rise lot, rain sensor equipment may cost approximately $150.

Savings from water conservation would be 12-15% or $125 per season (at $1.00/m3).Simple payback would be 1.5 years.

LANDSCAPE PRACTICES

THE ISSUES





Appropriate and well-considered landscape practices offer designers theopportunity to achieve increased levels of occupant comfort as well as cost savings

through reduced resource consumption. Consideration should be given to waterconservation, seasonally appropriate design decisions and storm water management.Across Canada, water use more than doubles in the summer months. Most of this increaseis due to the watering of lawns and gardens, car washing and the filling of swimming

pools. This is typ ical of suburban areas, but highr ise water consumption also contributesto increased summer water use. This is the case for buildings with extensive landscapewatering requirements.

Through water conservation practices in landscape design, this phenomenon can bereduced. Energy consumption in highrise residential buildings can also be reducedthrough thoughtful landscape design practices. Plants provide the most economic meansof modifying microclimate around a building, and represent a small investment for largeenergy savings. Appropriate and well-placed plants will have an effect upon energyconsumption. Other devices such as landscape structures and site grading are alsoavailable to the landscape architect, and when employed correctly, can result in furtherenergy savings.

Storm water management represents a significant cost to municipalities, viainfrastructure required to transport and treat run-off. It also represents a cost to the

environment through non-point source pollution. This is the transfer of pollutants fromroadways and parking lots directly to water bodies via run-off. The landscape architectsas well as the civil engineer are able to offset these costs by using appropriate bestmanagement practices for storm water management. Many on-site devices are availablefor slowing and filtering storm water. Other strategies include minimizing the amount ofrun-off from a site as well as re-using it.

Key issues considered in this section include: Water-efficient landscape practices Energy-efficient landscape prac tices for summer and winter Storm water management practices.

DESI GN CONSIDERATIONSWater-Efficient Landscape Practices Reducing watering requirements by at least

50% is achievable when specifying a water-efficient landscape. There are many waterconservation practices that can achieve such reductions.





Rainfall Storage and Reuse

Rain diverted through downspouts into storage devices (cisterns, rain-barrels) can be used for irrigat ion. The “Rainfall Capture Potential” table provides an estimate of therainwater volume collectable from typical high-rise buildings across Canada. Storagedevices range in size. The Mountain Equipment Co-op Building in Ottawa has a rainstorage container of 65,000 liters. It is 2.4 m (8 ft) in diameter and 6.0 m (20 ft) high.Considering that high-rise buildings can consume an average of 13,000,000 litresannually1, rain collection for indoor use does not seem significant. However, raincollection would likely meet a high-rise building’s irrigation requirements. Raincollection for irrigation helps to lower water demand during summer months whenconsumption is at its highest.

Locally Hardy PlantsMatch plant species to their local conditions. Locally hardy plant species, such as

native plants, are adapted to their indigenous climate. Under conditions similar to theirnative habitat, they have the ability to survive without human intervention. These speciesare therefore ideally suited to water conservation and are less costly to maintain. Native

plants are also more res istant to disease and infestation, and will benefit local insects and birds

Hydrozone PlantingGroup plants according to their water requirements. This will ensure water is not being wasted on plants whose needs do not warrant the frequency or quantity of adjacent plants with higher watering-demands.

Drought-tolerant PlantsWater-efficient plant specifications should include the use of drought-tolerant

species. Such plants, while not exclusively native species, require less water than plantsof similar size and structure. Drought-tolerant species lists will vary according tohardiness zones. These plants are often used in a type of landscape called a Xeriscape(from the Greek ‘xeros’ meaning dry).

Water-efficient I rrigationDrip irrigation is more water- efficient than sprinkler irrigation. Sprinklers can lose

approximately 25% to 50% of water content to wind and runoff . Drip irrigation reduces





evaporation through the application of water directly into the soil. It also limits irrigationto planted surfaces only, avoiding the unnecessary watering of sidewalks and pavement.

Drip irrigation can save 50% to 75% compared to a sprinkler system. Also, rain sensors prevent overwatering. Small and inexpensive ra in sensors can be installed to preventautomatic watering systems from activating during or after rainfall. Installation costs can

be recouped within two years through water costs savings.

LawnsLawns typically require 25 mm (1 in.) of water per week. This can add up to

750,000 litres annually for a typical high-rise building. In general, groundcovers requireless water because they have a larger root zone from which to draw soil water. High-useareas may be impractical for groundcovers, however. In such cases, droughttolerantturfgrasses are available and should be used (see Appendix 3: Turfgrasses for CanadianLawns in Household Guide to Water Efficiency, CMHC 2000). Also, only fertilize lawnsonce in the spring. Over-fertilized lawns grow beyond their limits and require increasedwatering.

MulchingBesides controlling weeds, mulches retain soil moisture levels and prevent soils

from overheating and drying-out by reducing evaporation. Mulches will also increase the

wetted surface area of soil under the mulch. Over time, organic mulches will also breakdown and improve the structure of soils, improving water infiltration. Propermulching practices will reduce the quantity of water required for irrigation; it can reduceevaporation and run-off by 75% to 90% over unmulched areas5. A mulching depth of 10cm will result in optimum moisture retention. Storm water management represents asignificant cost to municipalities, via infrastructure required to transport and treat run-off.It also represents a cost to the environment through non-point source pollution.

This is the transfer of pollutants from roadways and parking lots directly to water bodies via run-off. The landscape architect as well as the civil engineer is able to offsetthese costs by using appropriate best management prac tices for storm water management.Many on-site devices are available for slowing and filtering storm water. Other strategiesinclude minimizing the amount of run-off from a site as well as re-using it.

Energy-efficient Landscape PracticesA recent study by CMHC looked at the amount of fuel; fertilizer and pesticide use

by a var iety of landscapes and found that low-maintenance lawns required less energy





inputs than conventional lawns. Woodland-type gardens performed the best, however.The low maintenance lawn consists of hardy, drought-tolerant, slow-growing grass and

broad-leafed species, such as clover, that do not require frequent mowing. The woodlandshade garden is composed of native trees, shrubs and groundcovers. Xeriscapes andMeadows were also found to require minimal energy inputs. Xeriscapes consist of plantssuited to local rainfall conditions and require almost no watering. Meadows feature nativegrasses and wildflowers. Graphs at the left illustrate these comparisons.

SummerUse plants and landscape structures to reduce summer heat gain by:

Shading the building from direct solar radiation, Divert ing or channelling air movement away from or towards the building, Creating cooler temperatures near buildings through evaporation and transpiration.

The Heat Island EffectThe heat island effect is the phenomena of higher temperatures occurring in

urbanised areas relative to their suburban and rural surroundings. On warm summer days,the air in a city can be up to 5°C hotter than its surrounding areas. One reason for this isless vegetation in urban areas to intercept solar radiation, and cool the air with thetranspiration process. Transpiration is the process of water loss to the atmosphere throughliving-plant surfaces.

At the microclimate level, vegetation can directly reduce surface temperaturesthrough shading and the interception of solar radiation. Trees can reduce the temperaturein their immediate vicinity by up to 5°C from shading alone. One mature beech forexample, will shade 170m2 of surface area . Air temperatures above vegetated areas can

be up 8 to 14°C lower than over asphalt or concrete areas of equal size. As a result, urbanvegetation can alter the surface energy balance within a localised area and result in lowerambient temperatures.

On a local climate scale, vegetated areas will lower air temperatures through the process of transpiration. A 21-meter canopy tree, for example, can transpire theequivalent of 375 litres of water per day, which has the cooling effect of 5 air-conditioners operating for 20 hours. This cooling effect is the result of evapotranspirationand lowers ambient daytime temperatures.

Tree canopies can also slow the escape of heat from urban surfaces at night.Combined, these effects lower ambient temperatures. More vegetation lowers airtemperature, reducing the need for air-conditioning and lowering energy consumption.





This translates into direct cost savings to residents. It also can reduce global warming(less electrical demand implies less burning of fossil fuels at power generation plants).

Recomm ended Practices Use rooftop plantings to reduce heat absorption into buildings through their roofs

Plant broad-leaf deciduous shade trees to intercept solar radiation near ground level parking areas and other paved surfaces.

Acer platanoides will allow only 10% of solar radiation to penetrate its canopy insummer, while allowing 65% in the winter. Shaded areas can be as much as 10oCcooler than areas in full sun.

Plant self-supporting vines to climb south facing walls to reduce summer solargains. A 16-cm blanket of plants can increase the R-value of a wall by as much as30%5. Less vigorous species will not compromise cladding.

Plant deciduous trees to shade the first 3 to 5 storeys of an apartment building’ssouth and/or west elevations.

Stormwate r Management Practices

Imperviousness

Factors affecting runoff quantity and quality inc lude soil type, land cover, slopeand imperviousness. Imperviousness radically alters the water balance of a site byincreasing runoff volume and peak discharge. This is a major contributor to water

pollution. Urbanisation results in more hard surfaces, soil compaction and lessstormwater absorption. Under forested conditions only about 6% of total rainfall becomesrunoff. Within urban settings, as much as 90% of rainfall can become runoff. There is aninverse relationship between imperviousness and runoff quality. Runoff from urbansources represents a threat to receiving water bodies. It contains high concentrations ofnutrients (phosphorous, nitrogen), suspended solids, organic carbon, bacteria,hydrocarbons, trace metals, chlorides (salt) and debris.

Runoff also results in increased peak storm discharges causing erosion andsedimentation. Even small increases in impervious cover can effect water bodies. Forexample, stream degradation occurs even when imperviousness increases within a givenwatershed by as little as 3 to 10%. The imperviousness of a high-rise building lot istypically 50-70%, but can be as high as 85% . While the highest proportion of urbanimperviousness is transportation-related (60% to 70%) , decreasing lot imperviousness isstill an important overall strategy.





Best Management Practices for StormwaterBest management practices (BMPs) are accepted methods for reducing runoff

quantity and increasing its quality. In order to decrease the impacts of urbanisation, manycommunities in North America have adopted these practices (Bellevue, WA; Baltimore,MD). Detaining water on-site provides the fundamentals for water quality treatment.Urban phosphorus loads can be reduced when BMPs are used. BMPs include stormwater

ponds, wetlands, filters and inf iltration prac tices. BMPs can reduce phosphorus loads byas much as 40% to 60%6 and offer added amenity.

Runoff DiversionWhere water runs from impervious surfaces onto absorptive surfaces, runoff is

minimised. By us ing curbs and berms to divert stormwater from impervious surfaces andreusing it when possible, urban runoff can be greatly reduced. One method foraccomplishing this is to direct rainwater into swales, infiltration basins and trencheswhere it can infiltrate into the groundwater. One of the more common stormwatermanagement mechanisms is the drywell or ‘french drain’. Manufactured sediments trapsare also available that intercept runoff from drainage areas, and slowly release it whiletrapping sediments.

Land CoverComplex land covers result in less runoff because they tend to intercept more

precipitat ion. The most complex land covers are highly layered plant communities withvast amounts of leaf area that must be wetted before runoff occurs. Urbanisation tends tolead to a simplified land cover, causing an increase in runoff volumes.

Green RoofsGreen roofs offer three important benefits concerning stormwater management.

They retain, filter and slow down stormwater. Green roof systems have been observed toreduce stormwater discharge by as much as 90%. On average, green roofs retain 70%-100% of summer precipitation, and 40-50% of winter precipitation that falls on them. Agreen roof acts as a natural filter for discharge that does occur by filtering out heavymetals and nutrients carried by rainwater. Its absorptive quality (10-15 cm of runoffretained with a 20-40 cm layer of growing medium) also slow downs discharge, reducingthe risk of flooding.

OCCUPANT COMFORT – NOISE

THE ISSUES





Noise emanating from neighbouring apartments, common areas, buildingmechanical and plumbing systems and noise from outdoors can reduce occupant comfort

in high-rise buildings and can also become the source of litigation. Noise reaches building occupants through the airborne transmiss ion of sound, and through thetransmiss ion of vibrations through the structure of the building. The sources of disturbingnoises are many. They include exterior traffic and aircraft noise, and interior noises fromneighbouring suites generated by T Vs, stereos and other appliances. The buildingsystems themselves are also the sources of mechanical, plumbing, fan, diffuser and otherHVAC noises. Recent research for CMHC and IRC has resulted in the development ofrecommended practices which can minimize noise problems in multi-unit apartment

buildings.

STC RatingsSTC (Sound Transmission Class) ratings are used to describe the performance of

assemblies in reducing airborne sound. While higher than current Code requirements, theSTC ratings presented in the chart below will provide enhanced building comfort.

IIC RatingsThe IIC (Impact Insulation Class) rating applies to noise transmission due to

structural impact and vibration through floor and ceiling assemblies. The ratings in theattached graphic illustrate improved design objectives.

DESI GN CONSIDERATIONS Noise control s trategies must be addressed at the design s tage, as retrofit costs to

improve acoustic performance can be very high. Designers must consider the noiseimplications of the architectural, structural, mechanical, and electrical design. Thedesigner must address sound transmission through airborne and structural routes.

VerificationSound levels should be verified by field measurements using the ASTME336

standard, allowing construction defects to be corrected prior to occupancy.





Doors

Noise transmission is a common complaint in h igh-rise buildings w ith pressurizedcorridors. More innovative ventilation strategies (such as compartmentalized suites) mayallow for better sealing of entry door systems. The accompanying chart demonstrates the

potential noise reduction from alternative door assemblies.

WindowsWindows have typically been the weakest acoustical link in exterior walls.

Improvements in windows for thermal comfort purposes (for example multi-pane glazing

and thermally broken frames) have also improved their acoustical performance. Soundtransmission (especially when close to transportation routes) can be reduced byincreasing glass thickness (laminated glass), and increasing the width of the air space

between panes. These two strategies can increase the STC rating by as much as 8 to 10 points. Eliminating rigid mechanical coupling of the window to the frame structure, usingresilient or gasketed mounting, will further enhance performance.

Air-Borne NoiseStrategies to deal with air-borne noise include:

selection of envelope and party wall assemblies with good sound insulationcharacteristics.

Impact NoiseStrategies to reduce noise transmitted through the structure include:

providing an improved f loor design e.g., a floating f loor above the structural floorand/or absorbent materials within the floor cavity,

providing an increase in floor layer mass and resiliently suspended ceilings, reducing the impact at source through the use of resilient materials such as carpet

and underlay (with due consideration to their effect on IAQ),





Avoiding flanking noise transmission through structure by using resilientconnections.

Mechanical Equipment Rooms1 Noise control measures for mechanical equipment rooms adjacent to apartment unitsinclude:

choose equipment designed for low noise emissions, use a floating concrete floor in the mechanical room, use resiliently suspended secondary isolation ceilings in the mechanical room, use cavity wall construction in the mechanical room, use sound absorptive treatment of the mechanical space walls and ceilings, eliminate structural connections to avoid flanking noise transmissions

Plumbing SystemsMeasures for controlling noise resulting from plumbing assemblies include:

maintain water pressures at a maximum of 35 psi, and velocities below 1.8 m/secin branch lines and 3.0 m/sec in main lines,

the use of plastic piping in the supply network will decrease noise transmission3 , supply pipes should be supported by vibration isolation mountings of resilient

material, where pipe ‘cross-overs’ occur in occupied space, pipes should be housed in

double Gypsum board boxes and lined with fibreglass batt insulation.

InstallationWhile good acoustic design is vital, it should be noted that poor installation

techniques can negate good design practices. For example, debris and waste constructionmaterial can create a noise bridge that results in flanking noise transmission despite acorrect overall design. Poorly installed resilient channels are also a common problem(often upside-down or installed into structural elements). Proper onsite training anddemonstrations for workers involved with walls and plumbing equipment would help toreduce poor installation.




5

CONCLUSION

A wide range of Economic, Technology, Socio-cultural, Environmental, andPublic Policy issues, illustrating ways to improve sustainability in high rise structures,and drawing out, where relevant, the opportunities or constraints applicable to them. Thekey to achieving high quality high rise structures is to look at the ideal and work back,rather than our traditional approach of an incremental improvement on the last buildingwe were involved with. Such as the impact on the city planning and the local community,cultural responses and shadows cast and wind impact.

Documents

Thesis Report - Highrise Constrxn.pdf