ICI Souvenir

IAStructE

Convention Centre, SCOPE Complex,Lodhi Road, New Delhi - 110003

Innovations in Enabling Works,Formwork & Scaffolding Systems

Workshop on

11-12 September, 2015

Supported by

IAStructE

Ofcial Media Partner Media Partner

Platinum Sponsor

BRIDGECON

Silver Sponsor

Exhibitors

ISG Softwares

Sponsors

Exhibitors

Innovations in Enabling Works, Formwork & Scaffolding Systems

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Table of Contents

• About ICI

• About the Workshop

• Committees

• ICI Governing Council Members

• ICI NDC, Executive Committee Members

• Programme

• Abstracts / Articles

1. Formwork Selection & Economics –The Success Key to Your Construction

2. Allround Scaffold: Ideal for High Rise Industrial Structures

3. MFS Aluminium Formwork System

4. Modern Formwork Systems – An Overview

5. Scaffolding & Formwork – Types, Materials and Usage

06

06

07

08

09

10

11 - 33

12 - 17

18 - 19

20 - 21

22 - 23

24 - 33


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About ICI

About the Workshop

Indian Concrete Institute (ICI) is the premier professional body for concrete technology with above 10,000 members with 31 centres spread across India. It has on its fold the captains of Construction Industry, Building material manufacturers, Leading Consultants & Civil Engineers, Contractors, Academi-cians and Educational Institutions. ICI was founded in 1982 with its headquarter at Chennai. The objec-tives of ICI are to promote growth of concrete construction and its sub-specialisations, to disseminate knowledge and to train personnel, to collaborate with national and International agencies in creating better understanding of concrete construction technology, to identify R&D issues, encourage outstand-ing achievements in concrete construction technology through its institutional awards etc. ICI organises periodical seminars, conferences, workshops and exhibitions on the subject and arrange lecture series on selected topics of relevance to concrete construction.

ICI has collaborations with American Concrete Institute, Asia Concrete Federation, Singapore Concrete Institute, and Concrete Institute of Australia etc. ICI publishes a quarterly Journal containing peer-re-viewed technical papers, technical abstracts from about 40 journals. ICI has also brought out a number of publication and monographs on various related topics.

Enabling works, formwork & scaffolding are essential parts of construction. Not only concrete, even steel construction often requires temporary structures and scaffolding. Elaborate temporary works are involved in the making of precast concrete for buildings and bridges. Precast segmental bridge requires carefully designed launching girder. Specialised pre casting yards are required for precast segmental box girder and precast pretensioned girder bridges. Transportation of precast/prefabricated members necessitates special tools, tackles, and special trailers. Specialised cranes, gantries and launching girders are required to erect these prefabricated elements. Special purpose derricks are used to lift and erect large span structures. Use of resin coated ply has given new dimensions to aesthetics of architectural fair faced concrete. Similarly use of high quality rubber form liner for the precast segments can provide excellent aesthetics. Tunnel form in aluminum is used for construction of prestressed floors in order to further enhance the speed of construction. Tall piers and chimneys employ slip forming / jump forming as an efficient means of construction.

Formwork and scaffolding system contribute to a substantial share of cost in concrete constructions. Speed of erection and ease of stripping contribute immensely towards the speed of construction. Num-ber of reuses influence the cost of construction. A flexible system allows for easy adaptability to handle complicated site requirements in practical applications. It should be safe to make it accident free, at the same time results in aesthetics and desired architectural finishing. Finally a good shuttering system ensures durability of concrete construction.

Considering the requirement of cost effectiveness, speed, safety and durability of the structure, it is essential that right system of enabling works, formworks and scaffolding system are selected for a particular application. With technological advancement and availability of a large no of systems, it is imperative that a practicing engineer should identify project requirements and analyze the formwork options to ensure best results.

With the objective of improving concrete construction in India, Indian Concrete Institute New Delhi Centre (ICI - NDC) is organising a two day Workshop to familiarise and enrich the Stake holders in the construction industry.


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Organising Committee

Technical Committee

Chairman:Abraham, K P, Chairman, ICI-New Delhi Centre

Chairman:Gupta, Vinay, TCPL

Members:

Members:

• Agrawal, Shailesh, BMTPC• Anchuri, S P, ICI• Bhachech H, Virag, Hi-Lite Aluminium Formwork• Byapari, Amitab, Mahindra Real Life Spaces• Chauhan, Kishore Singh, UltraTech Cement Ltd• Das, Supradip, Consultant• Gaggar, Shashi, UltraTech Cement Limited• Ghanti, Rudrabir, Durabuild• Heggade, V N, Gammon India Ltd• Jairam P, Afcons Infrastructure Ltd• Joshi, Mukund, PWD, Delhi• Kataria, Rajan, DMRC• Khandelwal, Pradeep, EDMC• Kumar, Arun, UP Housing Board • Kumar, Mithilesh, Layher Scaffolding Systems • Kumar, Rajeeb, UltraTech RMC• Kurian, Jose, ICI• Lakhani, Raj, PERI India Pvt Ltd• Manjunatha, L R, JSW Cement

• Mehta, Rahul, L&T• Mishra, Santhanu, Pranav Constructions• Mittal, Vikas, Nova Plasmold• Niranjana, P, L&T• Pradeep, K P, Master Builder• Rawal, Mayank, Asian Laboratories• Robinson, Jim, MFE Formwork Technology• Roy, Debashish, Vollert• Sahai, Paramjit Singh, EPA Construction• Saraf, Sunil, Simplex Infrastructure Ltd• Saraswati, S, President, ICI• Sarkar, Amitendra, Doka• Seth, P K, NBCC• Shanmugam, Muralidharan, Lhita Engineering Services Pvt Ltd• Sharma, Rohit, Maini Scaffolds and Formwork System Pvt. Ltd• Singh, D P, DDA

• Bhattacharjee, B, IIT Delhi• Fassler, Andreas, Bridge Lab• Grover, S K, Slipco• Gupta, R K, Bridgecon• Kalgal, M R, UltraTech Cement Ltd.• Krishnamurthy, P, McAlloy• Kumar, Jayesh, PWD, Delhi• Lakshmy, P, CRRI• Mahajan, S L, BM & Associates

• Maiti, S C, UltraTech Cement Ltd.• Manjure, P Y, Freyssinet • Meyer Max, VSL• Miranda, Mario, Studio Miranda• Pal, Kamalika, Hilti India Pvt. Ltd.• Patanker, V L, IAHE• Sharma, A K, CPWD• Tandon, Mahesh, TCPL

Organising Secretary:Bansal, Shishir, DTTDC, Delhi

Co-chairman:Garg, B D, Northern Railway


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ICI Governing Council Members

• Saraswati, S. Dr., President

• Gangopadhyay, Partha Er., Vice-President (E)

• Gupta, Vinay Er., Vice - President (N)

• Kalgal, M.R. Dr., Vice - President (S)

• Tayade, K. C. Er., Vice President (W)

• Radhakrishnan, R. Er., Secretary General

• Chaudhury, Ganesh. P. Er., GC Member

• Chaudhary, Subrato Dr., GC Member

• Jain, S.K. Er., GC Member

• Jain, Ish Er., GC Member

• Jayasankar, K.Er., GC Member

• Kurian, Jose Er., Immediate Past President

• Kulkarni, V.R. Er., Past President

• Manjunatha, L.R. Er., GC Member

• Moorthy, K.G.K. Mr., GC Member

• Naik, Vivek Er., GC Member

• Pofale, A.D. Dr., GC Member

• Pradeep, K.P. Mr., GC Member

• Srinivasan, Prakash. Er., GC. Member


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ICI NDC, Executive Committee Members

• Abraham, K.P. Er., Chairman-NDC, Chief Engineer, CPWD, India

• Chauhan, K.S. Er., Hony. Secretary-NDC, Ultra Tech Cement Ltd., India

• Mehta, Rahul Er., Joint Secretary-NDC, L&T Ltd.

• Bansal, Vivek Er., Hony. Treasurer-NDC, Suptdg. Engineer, DTTDC, India

• Bansal, Shishir Er., Chief Project Manager, DTTDC, Delhi

• Bhattacharjee, B. Prof., Professor, Civil Engeering Department, IIT, Delhi

• Bhowmick, Alok Er., Managing Director, B&S Engg. Consultants Pvt. Ltd.

• Das, Supradip Mr., Consultant, Buildtech Product I. Pvt. Ltd

• Ghanti, Rudrabir Er., Management & Engineering Consultant, Dura Build Care Pvt. Ltd

• Gupta, U.K Er., Vice President, Jaiprakash Associates Ltd, Former Dir. (Tech.) SCOPE

• Gupta, Vinay Er., Vice President- North, CEO, TCPL

• Kumar, Rajeeb Er., DGM, Zonal Head - Technical UltraTech Concrete, India

• Kurian, Jose Er., Honorary Member, Immediate Past President,Chief Engineer, DTTDC, Delhi

• Maiti, S.C. Dr., Former Joint Director, NCCBM

• Rawal, Mayank Er., Director (Technical), Asian Laboratory


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Programme

DAY 1: 11th September, 2015 (Friday)

Registration 0845 hrs - 0945 hrs

Inauguration 0945 hrs - 1030 hrsChief Guest: Er. Mangu Singh, MD, DMRCKey Note Address: Jim Robinson

Tea Break : 1030 hrs - 1100 hrs

Session 1: 1100 hrs - 1300 hrs

Chairperson - Dr. A K Mullick Co- Chairperson - Shashi Gaggar

Theme : Modern Formwork Systems

TopicAuthor

Monolithic Formwork Technology Er. Rohitt Sharma

Topic

Author

Most Modern Methods of Construction:Tunnel form Er. Jignasu Mehta / Er Thierry Geoffroy

Topic

Author

Climbing Formwork Systems and Modular ScaffoldingEr. Raj Lakhani / Mr. Anibrata Routh

TopicAuthor

Controlled Permeability Formwork LinerProf. B. Bhattacharjee

Lunch Break : 1300 hrs - 1400 hrs


Chairperson - Er. Raj LakhaniCo-Chairperson - Dr. S. C. Maiti

Theme : Enabling Temporary Works & Architectural Fair Faced Concrete

Topic

Author

Smart Dynamic Concrete for Monolithic Formwork ConstructionEr. Nilotpol Kar / Er. Amol Patil

Topic

Author

Optimising Project Schedule Through Innova-tive Construction Method - A Case StudyEr. P. Niranjana

Topic

Author

Formwork Issues in Multi-storeyed Building- Shoring and Reshoring Dr. Neeraj Jha

TopicAuthor

Industrial Application of Scaffolding Er. Mithilesh Kumar

Topic

Author

Lean Digital Construction Project Manage-ment: The new way of delivering Projects Cheaper, Faster & BetterEr. Subhash Rastogi

Tea Break : 1530 hrs - 1600 hrs


Chairperson - Uday VartakCo-Chairperson - Mayank Rawal

Theme : Lifting, Transportation, Handling andErection & Formwork Materials

TopicAuthor

Issues related to Slipform in Chimneys Er. Ravindra Shah

TopicAuthor

Plastic Formwork SystemEr. Vikas Mittal

Topic

Author

Precasting and Launching of Full Span Pre-cast Pre-tensioned Box GirdersEr. R. K. Gupta

Topic

Author

Slip Forming of Deep Under GroundStructuresEr. S. K. Grover

TopicAuthor

Tunnel Formwork Dr. Rajiv Dua

DAY 2: 12th September, 2015 (Saturday)


Chairperson - A K SharmaCo-Chairperson - Shishir Bansal

Theme : Codal Provisions & Safety

TopicAuthor

Codal Provisions and Importance of DesignEr. Vinay Gupta

Topic

Author

Temporary Works- Basic Approach According to British CodeEr. K. B. Rajoria

TopicAuthor

Enabling Works of Signature BridgeEr. Sanjib Konar

Tea Break : 10.30 hrs - 1100 hrs


Chairperson - Er. Mario De MirandaCo-Chairperson - Rajeeb Kumar

Theme : Scaffolding Systems & Formwork Failures: Case Studies

Topic

Author

Innovative Methods & Equipment in the Con-structions of Cable Stayed Bridges Er. Mario De Miranda

TopicAuthor

Erection & Launching Systems Er. Vinay Gupta

TopicAuthor

Steel Bridges of Jammu- Udhampur Er. B. D. Garg

TopicAuthor

System Formwork & ShoringEr. Suraj Pal Singh

Valedictory Session : 1300 hrs - 1400 hrs

Lunch

ARTICLES


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Appropriate selection of a formwork system is a crucial factor in successfully completing most building projects. However, in practice, selection

of an appropriate formwork system has traditionally depended mainly on the intuitive and subjective opinion of practitioners with limited experience. This article discusses the guidelines on how to choose formwork, factors affecting the selection, economics involved in formwork and the present scenario of formwork in India. This can assist engineers to determine the appropriate formwork system at the inception of future projects.

Introduction

Formwork is a die or a mould, including all supporting structures, used to shape and support fresh concrete until it attains sufficient strength to carry its own weight. It should be capable of carrying all imposed dead and live loads apart from its own weight. A formwork system is defined as “the total system of support for freshly placed concrete including the mould or sheathing which contacts the concrete as well as supporting members, hardware and necessary bracing”. However, “System” implies a fully compatible arrangement of formwork with a minimum of individual components with reusable elements intended to solve each forming task thereby rationalizing the forming work.

Figure 1 - Main cost type in a typical building project

Formwork system is among the key factors determining the success of a construction project in terms of speed, quality, cost and safety of works. Nowadays, most projects are required by the client to complete in the shortest possible time as a means to minimise costs. For high-rise buildings, the most effective way to speed up works is to achieve a very short floor cycle - to have the structure of a typical floor completed in the shortest time. On the other hand, aiming purely at speed often contradicts the achievement of other quality standards. Problems such as

misalignment, misplacement, deflective concrete or holding up other works causing serious interruption can result.

The basic parameters of formwork are:

- Quality: in terms of strength, rigidity, position, and dimensions of the forms

- Safety: of both workers and the concrete structure

- Efficiency: in operation, the ease of handling, erection and dismantling, number of repetitions within the optimal limits

- Economy: the least cost, consistent with quality and safety

Percentage Of Formwork Cost In Total Construction Cost

In a typical multi-storey reinforced concrete building, formwork cost is the largest cost component. Formwork cost accounts for nearly 20-40% of cost of concrete and involves more than 60% cost of time. Overall formwork related cost have significant share i.e., 10% in the total construction cost. A large proportion of the cost of formwork is related to formwork labour cost. Significant cost savings could be achieved by reducing labour cost. An exemplary comparison reveals that the additional concrete use of up to 15% is economical than the handling of angular forming areas, since their assembly is rather time-consuming and the cost per square metre is higher than that for a straight surface.

An Integrated Formwork/Concrete Life Cycle

The process of providing formwork and concrete is highly integrated. In Figure 2, the left circle represents the formwork life cycle, while the right circle represents

Figure 2 - Integrated formwork/concrete lifecycle

“Formwork Selection & Economics –The Success Key to Your Construction”

Sameer S Malvankar, Deputy Manager-Engineering, Gammon India Ltd., Mumbai


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- Wall, Column - Girder form, Frame panel form, climb form or jump form

- Slab - Conventional timber form, Modular slab formwork, primary-and-secondary-beam method, Panel form, Drop head-beam-panel system, table form

- Repeated regular section - tunnel form, modular aluminium form

- Core walls, shells- Climbing formwork, Jump form and slip-form

- Precast structure- steel /aluminium mould forms

Classification according to materials of construction

– Timber : most popular formwork material - low initial cost - high adaptability to complicated shape - labour intensive and environmental unfriendly

– Steel: hot-rolled or cold-formed sections-heavy weight - suitable for large-sized panels

– Aluminium: stiff and light weight - higher material and labour cost - excellent finish

– Plastic: recyclable, tough, light weight

- Sacrificial concrete panels - Left in place formwork

Classification according to nature of operation

– Crane independent-

• Manually handled formwork

• Self-climbing formwork

– Crane-dependent formwork

– Gantry, travelling and tunnel type formwork system

Classification according to brand name of the product

Some companies in the market that are specialised in formwork manufacturing are DOKA, PERI, MEVA RMD, ULMA, TABLA, TITAN, MIVAN, HARSCO etc. Each has a different system for various structures.,

Figure 4 - Parties involved in formwork selection process

the concrete construction life cycle. The two intersection points represent the beginning and the end of concrete construction life cycle. It should be noted that the phases ‘cure concrete’ and ‘stripping of formwork’ are interchangeable depending on the type of structural element. For example, columns and walls are cured after stripping the forms while slabs and beams are cured before and then stripped.

Various Formwork Systems

Formwork can be classified according to a variety of categories as follows:

Figure 3 - Categories of formwork classification

Classification according to size

– Small-sized formwork

• Operation by workers manually

• Wooden and aluminium formwork

– Large-sized formwork

• Crane facilities are required in the operation

• Reduce the number of joints and to minimize the number of lifts

• Stiffening components -studs and soldiers

Classification according to location of use

Various elements in the structure have specific design and performance requirements in the use of formwork. Some systems are more adaptive for specific location of use, such as

- Irregular frame structure - Conventional traditional timber form


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Evaluation/Selection Criteria For Formwork System

Earlier formwork was once built in-place, used once, and subsequently wrecked. The trend today, however, is towards increasing prefabrication, assembly in large units, erection

by mechanical means, and repetitive use of forms. These developments are in tune with the increasing mechanisation of production in construction sites and other fields.

Formwork planning includes detailed layouts, cycle plans, calculation of optimum amount of material for the site, observance of fixed schedules and selection of the most appropriate and the most economic formwork system to be used at the construction site.

Formwork Selection Criteria

Internal Layout

Some buildings may have very simple layouts with a few in-situ walls and floor plates framed with regularly spaced columns, as seen in many commercial and office buildings. However, some developments feature very complicated load-bearing internal walls that can make the casting process difficult.

Structural Forms

Like internal layout, the structural form of buildings also affects the formwork options. For example, buildings with a structural core in the form of a vertical shaft limit the use of formwork systems other than those of a self-climbing nature. Buildings in flat slab design make table forms or flying forms the most obvious choice. For buildings with regularly arranged shear wall designs, the best selection is large-panel type steel forms or other types of gang forms.

Consistency In Building Dimensions

Some buildings may have non-standardised dimensions due to the architectural design and layout or to fulfill other structural requirements. These include the reduction of sizes for beams, columns and walls in high-rise buildings as the structure ascends. Formwork systems like the climb-

form or steel form, may be quite difficult to use in such situations; frequent adjustments of the form to meet the changes in dimensions may eventually result in incurring extra cost and time.

Headroom

Higher headroom increases the amount (height) of staging required and can also create accessibility and safety problems. It can also make the erection of formwork, ensuring formwork stability and the placing of concrete more difficult.

Building Span

Large building spans also create problems similar to those with high headroom situations. In addition, long-span structures generally have larger beam sections, heavier reinforcement provisions, or accompany post-tension works. This will further complicate the formwork’s design and erection process.

Repetitive Nature

High-rise block-shaped structures usually require highly repetitive cycles and this is favourable to the use of formwork. However, the degree of repetition in building with very large construction area like a podium or underground structures such as basements is limited and the use of formwork, as an expensive resource, becomes very critical.

Project Planning/Speed Of Work

The over-all construction sequence must be planned to use formwork in efficient manner and to permit the optimum investment in formwork to meet schedule requirements. Contractor should plan formwork and job sequence at the time of making a bid. Project planning such as the phasing or sectioning arrangement, integration

Figure 5 - Process cycle for formwork selection


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of the structure, site layout and set-up arrangements or hoisting provisions and concrete placing facilities are influencing factors when considering formwork selection and application.

When working with buildings with large construction areas and horizontal spread, projects can be expedited by the introduction of additional sets of formwork, to create more independent work fronts. This will, of course, increase the cost of construction. For high-rise buildings, increasing the number of formwork used cannot always expedite the project, for the critical path still depends on the floor cycle. However, a properly selected, designed and arranged formwork system will increase work efficacy for each typical cycle. In some cases, adding half or a full set of formwork, especially for the floor forms, may help to speed up the cycle as the additional set can provide more flexibility when the form is struck at an earlier time.

Construction Process, Methods

For selecting formwork one must know the sequence of construction activities and methods to be followed. Construction method will always give idea about interdependency of the activities, specifications and additional requirements in pour. This will enable us to workout appropriate system which fulfills the construction needs.

Site Logistics

Exceptionally small or very large sites, sloped or very crowded sites, proximity to sensitive structures, sites where other major activities are underway, or sites with many physical or contractual restrictions will increase the difficulty of working with formwork. There is no specific solution to improve the situation in general and problems are tackled according to individual circumstances.

Accessibility to work during the course of construction is also important. Accessibility problems may be created through segregation, temporary discontinuation, or blocking of the layout by the partially completed building, or, in cases of constructing a shaft-type core wall, the shaft may stand independently for a long period of time before it is connected to the horizontal elements. Proper access to all components should be considered while planning a site layout.

Climate Condition

Formwork systems are sensitive to weather conditions. Typically, in vertical forming systems, the newly placed concrete is supported by the wall already cast below it. The lower wall section must get sufficient strength to support the fresh concrete above. The rate of strength gain of lower wall is influenced by the ambient temperature, moisture content, and the freezing and thawing cycles.

Another factor that affects the economy of the selected system is the effect of stopping formwork activity and concreting because of extreme weather conditions. In the case of a slip-form, the work is usually continuous, round the clock. If the slip-form stops because of weather conditions, it may impact structure as well as cost.

Labour Efficiency

Considering the availability and qualification of the work force, improving labour cost efficiency is a major factor, especially in markets experiencing a building boom. Here, the qualification of workers tends to be low in relation to ever higher demands posed by construction methods.

Cost of Formwork System

This is a vital factor for deciding formwork system as one must know the capital provision for formwork in the project. It is always beneficial to work out these details at the time of bidding.

Cost is Influenced By Three Components:-

Initial Cost or Make-Up Cost: Includes cost of transportation, materials, assembly and erection

Reuse Cost of Formwork System: The formwork system cost goes on reducing as we increase reuse of the same. A careful balance between cost, speed, performance and the quality of output should be properly considered when making the selection.

Maintenance & Storage Cost: It includes cost of stripping, repair, storage, etc. Formwork materials are a valuable asset of company, If proper care is taken during handling and storage, much return is obtained on the investment. Formwork needs to be handled correctly, maintained, repaired if necessary and finally, cleaned regularly. Avoiding damage reduces costs incurred. Proper storage of formwork materials gives easy reconciliation, faster retrieval of material, better space management and helps avoid unnecessary expenditures, improve safety at work place.


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Availability Of Lifting Devices (Crane time)

These include considerations of whether there will be lifting appliances provided for the erection of formwork; whether these appliances will be able to access the work spot to assist in the operation as the structural works proceed; whether any special equipment will be required for striking the forms; and how the removed formwork panels can be transported to other spot to continue work.

Characteristic to high rise building sites is the confined and congested space availability for working. Crane time and space is regularly limited. In general, reinforcing (rebar) activities are most critical, since lifting the reinforcement to building level is the most crane-time consuming job of all. Thus, the capability of formwork to rely less on or be used independently of crane time is critical in high rise construction.

Simple Logic Of The System

Formwork system ought to be self-explanatory to use, this automatically eases the usage for the engineers/supervisor and also the labourers who are end users of the system.

Working Safety

Formwork should be self-securing with safe access and working platforms. Thus, it is not left to the end user whether they take safety measures or not. Creating a safe work environment for the entire work force involved in the construction process, has become the pivotal issue in emerging construction markets.

Special Requirements On Concrete Surface/Finish

Fair-faced concrete demands very high quality formwork in terms of surface treatment of the panels, tightness of the formwork joints and in dimensional accuracy. Requirements are slightly relaxed where the concrete surface is to be finished at a later stage.

Area or volume of cast per pour

The optimum volume of cast per pour depends on the types of formwork used, the particular elements of structure to be placed, the actual scale of work, and different levels of provisions of plant facilities.

Involvement of other construction techniques

Tensioning and prefabrication activities are often involved in construction. This may create certain impacts on the use of formwork, especially where precast elements are to be incorporated during the casting process. Provision should be made for temporary supports or slot spaces and box out positions in the formwork for the precast elements, or extra working space for placing stressing tendons and onward jacking.

Provision Of Construction Joints In Structures

Many a times a large number of construction joints are inevitable in a large structure because of the subdivision of works into effectively workable sizes. The provision of construction joints can challenge the output and affect the quality of the concrete. Careful selection should be made to ensure a particular formwork system can satisfactorily allow such arrangements.

Inventory - The Fewer, The Better

The most frequent time & cost consuming activity of formwork assembly is the loose and small components/accessories. The lesser inventories will help to reduce risk of losing parts and provide ease in construction.

The Indian Scenario

In the past, India had been lagging behind over the other advanced countries in applying advanced and safe concepts for formwork in reinforced concrete construction resulting in a poor surface quality, wastage and low productivity of the people involved in concrete construction. This unfortunate situation continued for a long time because of availability and use of very cheap unskilled labour and very few skilled personnel who have had professional training for formwork jobs.

With increasing demand and competition and reducing project completion times, there have been significant developments in the construction industry in terms of experience and mastering of the required managerial, construction or engineering skills for handling very large


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and complex projects. At the same time, the motivating factors highlighted above have created an eagerness and readiness within the industry to advance. From the building construction point of view, the use of better formwork systems is no doubt a very direct way for introducing innovative methods in the construction of buildings.

- Formwork labour cost is so immense that any innovative system resulting in a labour cost reduction is highly lucrative.

- Fulfilment of fast track construction schedule provides fewer choices, one of which is to adopt more innovative formwork systems.

- Traditional systems can hardly satisfy the tight quality standard that is required nowadays.

- Similarly, traditional systems can hardly satisfy current safety and environmental standards.

- The accumulation of experienced crews makes the application of more sophisticated formwork systems more reliable and economical.

- Many developers view the application of innovative technology in the construction process as a positive image-building factor. Major systems dominate today’s state-of-the-art formwork approach in high rise construction.

- Slab edge protection by screens, providing a safe working environment on the construction levels

- Modular slab formwork, operated independently of the crane time, adapted flexibly to different building geometries and floor layouts

- Undisturbed shoring for slab with drop beam systems

- Frame formwork for columns and walls

- Crane dependent climbing formwork for shear walls/mega columns

- Crane independent climbing formwork for core

Conclusions

1. Selection of formwork system is highly dependent on individual site/project environment

2. Economy of formwork can be achieved with seamless collaboration between owner, architect, designer teams and contractor. And it can aid in the effective use of advanced formwork systems

3. The structural form of the building is one of the critical factors to determine the choice of formwork

4. System products contribute much in the success of formwork application

References

1. ACI 347-04, “Guide to formwork for concrete”, American concrete institute, 2005

2. Hanna A. S. & Sanvido V.E. , “ An interactive knowledge based on formwork selection system for building”, Computer integrated construction, 1989

3. Hurd M. K., “Formwork for concrete”, American concrete institute, 1915, 6th edition

4. Raymond W. W. M. , “Application of formwork for high rise and complex building structures- Hong Kong cases”, Division of building science & technology, city university of Hong Kong.


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Allround Scaffold: Ideal for High RiseIndustrial Structures

Mithilesh Kumar, Director, Layher Scaffolding Systems Pvt Ltd

Layher, the German Company, produces high-quality scaffolding systems in Germany. Layher has world-wide presence with more than 40 sales subsidiaries.

The products are being used by industries like Construc-tion, Cement Plant, chemical plants, power plants, at ship-yards and offshore.

More Possibilities - Layher Products and Services

Layher’s present product characteristics and services help customers achieve long-term success and increase the profitability of their companies. The Layher Allround Scaffolding has been established as a synonym for modular scaffolds on the market. The Allround Scaffolding offers unsurpassed versatility to be used in construction sites, chemical industry, power plants, aircraft, shipyards, event sector, theatres and arenas.

Application of Layher Allround Scaffold in Cement Industries

Cement silos are either part of the production process in integrated cement plants or they can also be the key part of distribution terminals. For the cement industry

these storage silos are very important because this allows a continuous production, while the cement dispatch can be discontinuous. Largest cement storage silos in

the cement industry are built with diameters up to 30 m while typical silos for the storage of 20000 t cement are typically 4 to 30 m in diameter and 20 to 72 m in height. It is clear that such silos require an efficient and trouble-free emptying. Accordingly highest requirements are given to overall plant reliability and practically 100% availability. To achieve a high availability flow problems have to be strictly eliminated. From the theory of flow in silos it is well-known, that this can only be achieved with mass-flow. For cement silos, the central cone version has become the predominant design. On the one hand, the central cone has a displacement function for the material in the silo; and on the other hand several designs especially for multi-compartment designs become possible. Multi-compartment silos are used for producing special cements from a number of main and secondary cement components.

Not only has the shape of the building reminded of a crystal, but also the surface of the façade. To attach the Local Scaffolder solved this task technically with the Layher Scaffolding and Technical team: section by section they adapted the scaffold to the slope of the building with various brackets on the inside and then shifted it inwards by one scaffold width. Scaffold was anchored with the help of Layher Anchoring equipment, even the increased wind loads could be transferred without putting unnecessary strain on the structure.

The construction of Scaffolding for maintenance of Silo is a challenging task due to wind pressure. It includes selection of support systems (scaffolding with permanent structure) and avoiding obstructions by bracket or cable tray around the silo. Layher Allround Scaffolding systems provide unique, bolt-less connection technique, the patented Allround joint has replaced the conventional scaffold technique especially in construction of Scaffold for Silo up to 72 metre height. Allround Scaffolding can accommodate all types of high loads and is the ideal system for all kinds of support scaffolding. Allround scaffolding has an efficient solution to deal with all challenges, regardless of whether they involve false work at great height or round inner scaffolding.

It needs to be built in a modular scaffolding system for maintenance of Silo and high rise Industrial structure. Cement Plant situated near the sea shore necessitates to take care of wind force.

Anchoring, essential for the stability of the scaffolding


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must be continually installed as scaffolding assembly progresses. Only provide anchoring on sufficiently can be tested strong components, if necessary, the anchoring surface by pull – out tests. A check can be dispensed with if sufficient load- bearing capacity can be assessed on the basis of professional experience and the service e value of the anchoring force does not exceed 1.5 KN or in the case of reinforced concrete.

Connect Horizontal Ledger with two standard couplers with very wide scaffolding structures, it must be necessary to anchor with the aid of a horizontal ledger. The selection of anchoring configuration depends on the bay width, the load on the scaffolding, live load, wind load and the structural height of the scaffolding. As the load on the scaffold increase, the anchoring configuration must become denser in order to pass the force safely into the anchoring surface. The dense anchoring configuration shall lower the force on the individual wall ties.

Landing Type Aluminium Stair Access up to 72 Metre Height

With Layher Modular stair tower, access possibilities that always fit and that match the system. With the landing type Aluminium stair tower, it is simple to construct a 4-standard stairway tower, either integrated into the scaffolding or as a free-standing access structure

anchored onto the building. There is no hindrance to work on scaffolding by using Aluminium landing type stairway. Furthermore, a distinction is made between independent access structures that are anchored to the silo and access structures that are integrated into the Scaffolding. The maximum permissible load bearing capacity of Aluminium stair tower is 2.5 kN/m2. It is easy to construct up to 72 m height due to light weight components. Attach the necessary anchoring continually in accordance with structural requirements. Unlike external platform stairway access, the platform stair tower has the advantage that work being done inside the scaffolding is not hindered by people ascending or descending.

With allround Scaffolding, thanks to 8 different connections possible at the Allround connector and the variable choice of angles, it is a simple task to erect scaffolding around curved surfaces. Possible connections and variable angle selection, curved surface can be enclosed with scaffolding without any problem. To build economical large-diameter scaffolding, the largest possible bay widths must be planned. In systems solutions using Allround equipment, two variants have proven their worth in practice: in the first variant, only system bays are used, while the second variant uses intermediate bays. In both cases, it is recommended that at least the last bay be selected as an equalizing bay.


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MFS Aluminium Formwork SystemRohitt Sharma, Director, Maini Scaffolds & Formwork Systems Pvt. Ltd

India being the second most populous country in the world with a growing population of 1.28 billion, is facing huge shortage of housing units. Requirement of

housing units due to urbanization is increasing day by day. Different government bodies launch various schemes to ful fil this demand, but due to delay in the delivering of these units, the gap between demand and supply is increasing rapidly. Use of conventional methods of construction consumes more time, which leads to delay in completion of any project. Desired quality is not achieved and safety of workers is compromised. It is therefore obligatory to work out a method or a scheme, where speed and quality of construction are controlled automatically by a systematic approach.

The Construction Industry in a growing economy like India has reached a stage where mechanization is essential for survival. The shortage of skilled labour and spiralling cost of labour is indeed disturbing. Capital is in short supply and hence expensive. Interest rates for construction industry is one of the highest in the world, which means the period for which capital is deployed is very critical. Therefore, it is imperative that our esteemed customers choose right service partner and systems, which will eventually lead to financial and business viability.

“MFS Aluminium Formwork” is a unique system, which ensures monolithic concreting that eliminates one stage of concreting. Entire forms for Vertical (Shear Walls / Columns) and Horizontals (Beams and Slab) including staircases, balconies, window hoods, storage lofts etc. are set at one stage for single pour, resulting in accurate finish with consistent quality.

“MFS Aluminium Formwork System” is an advanced formwork technology highly suitable for mass housing construction, where quality and speed can be maintained at a reasonably high level. Speedy construction, consistency

in architectural dimensions, excellent finish, and less dependency on skilled workers and simplicity in erection and de-shuttering makes “MFS Aluminium Formwork System” more viable and preferred formwork technology for construction of mass housing projects. Following are some unique advantages:

– Shortens construction period (7 - 8 days slab to slab cycle is achieved)

– Reduces construction cost

– Greater strength and durability of structure

– Monolithic crack free structure

– Environment friendly

– Eliminates entire plastering

– Seismic earthquake resistant structure

– Civilized method of construction


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MFS provides end-to-end solutions viz. designing, manufacturing and professional after sales services (consisting of training & education for proper usage of MFS Aluminium Formwork System) ensuring more productivity at economic prices.

Designing of “MFS Aluminium Formwork System” is done with in-built Software. A Rotating 3D Model of entire unit along with individual panels is viewed for accuracy. Any overlaps or clashes are identified and removed at design stage prior to the generation and release of shop drawings, assuring flawless manufacturing drawings based on which entire system is manufactured.

Our competent and experienced team of design engineers ensures maximum repetitions of formwork in particular project for better viability, which ensures economy along with quality and safety.“MFS Aluminium Formwork System” is designed with maximum standard size inventory so that 60 - 65% of inventory can be reused in other projects. However, if floor-to-floor height is controlled, 70 – 75% of inventory can be reused making our system versatile and more economic.

We also provide technical design assistance for optimum usage of “MFS Aluminium Formwork Systems” enabling the customers to re-use maximum number of components in their future projects.

“MFS Aluminium Formwork System” is most suited formwork system for residential projects. Designed and manufactured as per Indian conditions, it ensures faster completion of project at optimum cost while maintaining high quality standards. Unlike the myth that Aluminium formwork can be used for structure with shear walls only, our system is designed for shear wall and column - beam structures as well. We firmly believe that Formwork System should be designed as per the structure and not Vice – Versa.

“MFS Aluminium Formwork System” is the front line product of “MAINI Scaffolds & Formwork Systems Pvt. Ltd. - Faridabad” and is being successfully used by reputed developers / contractors across India.

With annual manufacturing capacity of approximately 6 lakh square metre and implementation of latest and advanced techniques we always endeavour to be at the forefront of advancing formwork technologies and continue to bring our valued customer, the highest quality, best services and unsurpassed value. With the focus of core engineering skills and decades of experience towards taking an innovated approach to continually upgrade the system, we are continually adapting to rapidly changing demands of our valued customer.

Make in India

Make in India is a major national initiative, which focuses on maximum usage of equipment, which are manufactured in India. This comes, as a great opportunity for Indian manufacturers to compete with global agencies but at the same time it also requires quality deliverables as per global standards. We are fully geared to cater to Indian Construction Industry with best quality products, in-time deliveries and best technical services as we have firm belief in our team and its capability to face any challenge with positive attitude. It would be refreshing to see Indian formwork industry to grow to new heights. At “MFS Aluminium Formwork System “ we encourage this great initiative and shall contribute to make it successful.

We are determined for changing the mindset by delivering better quality products than any of the global players.-

“The success of any business is gauged by the capability of an organization to complete the job on time with budgeted resources. Time waits for no one. Aspirations can’t wait and ambition does not know tomorrow. We, at “MFS Aluminium Formwork System” believe that tomorrow is a day too late. We continuously strive to provide value for money to our clients enabling them to achieve the most cost effective solutions for their projects with high safety standards, excellent quality and unparalleled services. With excellent team work, we aim to turn our vision into reality NOT TOMORROW BUT TODAY”

We look forward to take “MFS Aluminium Formwork System”, to the next level with market goodwill of our satisfied customers. We welcome any suggestions from our esteemed readers for betterment of our products and services.


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Modern Formwork Systems – An OverviewKamalika Pal, Assistant Manager - C & A, Hilti India Pvt. Ltd.

The formwork industry has evolved significantly in the past few decades to keep pace with the changing requirements of the construction industry.

Traditionally, a formwork was considered to be good if it was able to withstand the construction load and was rigid enough to retain its shape. With time, this definition has also changed to accommodate aspects like flexibility, ease of use, cost effectiveness, etc. This definition of “good” formwork varies from project to project. In some projects, a light-weight and flexible formwork system capable of delivering a superior surface finish like fabric formwork system may be required and in other a more rigid system may be required. Different aspects like strength, stiffness, water tightness, robustness, ease of removal, standardization and safety may be considered while defining the required formwork system. Some of the common types of formwork for modern concrete construction are:-

Modular Formwork

These systems comprise of modular panels which can be reused on a wide variety of jobs. Steel frame with plywood is commonly used to form the modular panels. The support and fixing required for modular formwork are simple.

Slipforms

Slipform systems comprise of moving formwork. It may be used both for horizontal and vertical construction. For vertical construction, hydraulic jacks may be used to move the form after the concrete has gained adequate stiffness. The rate of slip forming may vary from 300–400 mm per hour for vertical construction and 300–500 m per day for horizontal construction. This type of formwork allows speedy construction with less area of formwork.

Gang Forms

Gang forms comprise of large panels which are moved as a complete unit using cranes. Modular panels are often used for gang forms. This system also allows speedy construction. Though these systems are expensive, the cost of formwork is often offset by multiple re-uses and the time saved. Some types of gang forms are listed below:

- Table Forms: Large sections of soffit form along with propping and bracing elements are fabricated into a single unit. These units are moved using cranes.

- Jump / Climb Forms: These systems are used for casting vertical elements. These systems are not labour intensive. These systems do not require cranes for handling as they comprise of simple mechanical means for handling. After striping the form, it is shifted to a new position and then re-aligned using its own in built jacking system.

Permanent Forms

Permanent forms are left in place to become part of the finished structure. The use of these systems minimizes the need for subsequent finishing operations. These systems sometimes also assist in taking some of the structural load.


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Fabric Formwork

The material used for fabric formwork is usually highly flexible. A variety of shapes can be cast using fabric formwork.

Conclusion

Each system has its own set of advantages and disadvantages. It is very important to select the right formwork system based on the project requirement. But, the desired results depend not only on the selection of the formwork itself but also on the tools used to ensure proper erection, support, aligning and levelling. If the concrete is not levelled properly, it could lead to non-conformance in casting tolerance, improper form operation, and difficulty in stripping, damage to the casting or form components and wastage. For example, the use of a rotating laser like Hilti PR3 when used for erection of modular formwork might result in better quality and cost saving compared to use of traditional levelling tools. Consider a 10 storied residential jobsite of 5000 metre-square area per floor. The deviations during pouring of concrete for casting of slab are generally around 10mm using traditional methods, which results in extra concreting of 50 metre-

cube. This will result in wastage of 350 cement bags for 5000 meter-square area per floor. With the help of PR3 the deviations can be controlled to ±0.75mm. Hence, a contractor can save up to 350 cement bags per floor with an added advantage that only one labour is required to check the levels and cover large areas with a range of 300m (diameter). In summary, formwork should not be considered just as means casting for but as an integral part of concrete construction. All stages from selection of the correct formwork system to execution are equally important.


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Scaffolding & Formwork – Types, Materials and Usage

Dr. R Kuberan, Senior Editor (Technical), Civil Engineering & Construction Review

ScaffoldingScaffolding, also called scaffold or staging, is a temporary

structure used to support a work crew and materials to aid in the construction, maintenance and repair of buildings, bridges and all other man-made structures. Scaffolding is also used in adapted forms for formwork and shoring, grandstand seating, concert stages, access/viewing towers, exhibition stands, ski ramps, half pipes and art projects.

There are four main types of scaffolding used worldwide today. These are Tube and Coupler (fitting) components, prefabricated modular system scaffold components, H-frame / facade modular system scaffolds, and timber scaffolds. Each type is made from several components which often include:

•A base jack or plate which is a load bearing base for the scaffold.

•The standard, which is the upright component with connector joins.

•The ledger (horizontal brace).

•The transom, which is a horizontal cross section load bearing component which holds the batten, board or decking unit.

•Brace diagonal and/or cross section bracing component.

•Batten or board decking component used to make the working platform.

•Coupler a fitting used to join components together.

•Scaffold tie used to tie in the scaffold to structures.

•Brackets used to extend the width of working platforms.

Specialized components used to aid in their use as a temporary structure often include heavy duty load bearing transoms, ladders or stairway units for the ingress and egress of the scaffold, beams ladder/unit types used to span obstacles and rubbish chutes used to remove unwanted materials from the scaffold or construction project.

Evolution

Sockets in the walls around the paleolithic cave paintings at Lascaux, suggest that a scaffold system was used for painting the ceiling, over 17,000 years ago.

The Greek historian Herodotus thus wrote of scaffold: “At first, it (the pyramid) was built with steps, like a staircase. The stones intended for use in constructing the pyramids were lifted by means of a short wooden scaffold. In this way they were raised from the earth to the first step of the staircase; there they were laid on another scaffold, by means of which they were raised to the second step. Lifting devices were provided for each step, in case these devices were not light enough to be easily moved upward from step to step once the stone had been removed from them. I have been told that both methods were used, and so I mention them both here. The finishing-off was begun at the top, and continued downward to the lowest level.”

The Berlin Foundry Cup depicts scaffolding in ancient Greece (early 5th century BC). Egyptians, Nubians and Chinese are also recorded as having used scaffolding-like structures to build tall buildings. Early scaffolding was made of wood and secured with rope knots.

Repair work on Buckingham Palace in 1913, under the scaffolding of

Patent Rapid


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Modern Era

In days gone by scaffolding was erect by individual firms, with wildly varying standards and sizes. Scaffolding was revolutionised by Daniel Palmer Jones and David Henry Jones. Modern day scaffolding standards, practices and processes can be attributed to these men and their companies. With Daniel being the better known and patent applicant and holder for many scaffold components still in use today, he is considered the grandfather of Scaffolding. The history of scaffolding being that of the Jones brothers and there company’s Patent Rapid Scaffold Tie Company Ltd, Tubular Scaffolding Company and Scaffolding Great Britain Ltd (SGB).

David Palmer-Jones patented the “Scaffixer”, a coupling device far more robust than rope, which revolutionised scaffolding construction. In 1913, his company was commissioned for the reconstruction of Buckingham Palace, during which his Scaffixer gained much publicity. Palmer-Jones followed this up with the improved “Universal Coupler” in 1919 - this soon became the industry standard coupling and has remained so to this day.

The advancements in metallurgy throughout the early 20th century saw the introduction of tubular steel water pipes (instead of timber poles) with standardised dimensions, allowing for the industrial interchangeability of parts and improving the structural stability of the scaffold. The use of diagonal bracings also helped to improve stability, especially on tall buildings. The first frame system was brought to market by SGB in 1944 and was used extensively for the post-war reconstruction.

Extensive scaffolding on a building in downtown Cincinnati, Ohio.

This type of scaffolding is called pipe staging

Scaffolding Today

The European Standard, BS EN 12811-1, specifies performance requirements and methods of structural

and general design for access and working scaffolds. Requirements given are for scaffold structures that rely on the adjacent structures for stability. In general, these requirements also apply to other types of working scaffolds.

The purpose of a working scaffold is to provide a safe working platform and access suitable for work crews to carry out their work. The European Standard sets out performance requirements for working scaffolds. These are substantially independent of the materials of which the scaffold is made. The standard is intended to be used as the basis for enquiry and design.

Materials

The basic components of scaffolding are tubes, couplers and boards. The basic lightweight tube scaffolding that became the standard and revolutionised scaffolding, becoming the baseline for decades, was invented and marketed in the mid-1950s. With one basic 24 pound unit a scaffold of various sizes and heights could be assembled easily by a couple of labourers without the nuts or bolts previously needed.

Tubes are usually made either of steel or aluminium, although there is composite scaffolding, which uses filament-wound tubes of glass fibre in a nylon or polyester matrix, because of the high cost of composite tube, it is usually only used when there is a risk from overhead electric cables that cannot be isolated. If steel, they are either ‘black’ or galvanised. The tubes come in a variety of lengths and a standard diameter of 48.3 mm. The chief difference between the two types of metal tubes is the lower weight of aluminium tubes (1.7 kg/m as opposed to 4.4 kg/m). However they are more flexible and have a lower resistance to stress. Tubes are generally bought in 6.3 m lengths and can then be cut down to certain typical sizes. Most large companies will brand their tubes with their name and address in order to deter theft.

Assembly of bamboo scaffolding cantileveredover a Hong Kong

street


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Boards provide a working surface for scaffold users. They are seasoned wood and come in three thicknesses (38 mm (usual), 50 mm and 63 mm) are a standard width (225 mm) and are a maximum of 3.9 m long. The board ends are protected either by metal plates called hoop irons or sometimes nail plates, which often have the company name stamped into them. Timber scaffold boards in the UK should comply with the requirements of BS 2482. Timber, steel or aluminium decking as well as laminate boards are used. In addition to the boards for the working platform, there are sole boards, which are placed beneath the scaffolding if the surface is soft or otherwise suspect, although ordinary boards can also be used. Another solution, called a scaffpad, is made from a rubber base with a base plate moulded inside; these are desirable for use on uneven ground since they adapt, whereas sole boards may split and have to be replaced.

Couplers are the fittings, which hold the tubes together. The most common are called scaffold couplers, and there are three basic types: right-angle couplers, putlog couplers and swivel couplers. To join tubes end-to-end joint pins (also called spigots) or sleeve couplers are used. Only right angle couplers and swivel couplers can be used to fix tube in a ‘load-bearing connection’. Single couplers are not load-bearing couplers and have no design capacity.

Basic scaffold dimensioning terms. No boards, bracing or couplers

shown

Other common scaffolding components include base plates, ladders, ropes, anchor ties, reveal ties, gin wheels, sheeting, etc. Most companies will adopt a specific colour to paint the scaffolding with, in order that quick visual identification can be made in case of theft. All components that are made from metal can be painted but items that are wooden should never be painted as this could hide defects. Despite the metric measurements given, many scaffolders measure tubes and boards in imperial units, with tubes from 21 feet down and boards from 13 ft down.

Bamboo scaffolding is widely used in Hong Kong, with nylon straps tied into knots as couplers. In India, bamboo or other wooden scaffolding is also mostly used, with poles being lashed together using ropes made from coconut hair (coir).

Basic Scaffolding

The key elements of the scaffolding are the standard, ledger and transoms. The standards, also called uprights, are the vertical tubes that transfer the entire mass of the structure to the ground where they rest on a square base plate to spread the load. The base plate has a shank in its centre to hold the tube and is sometimes pinned to a sole board. Ledgers are horizontal tubes, which connect between the standards. Transoms rest upon the ledgers at right angles. Main transoms are placed next to the standards, they hold the standards in place and provide support for boards; intermediate transoms are those placed between the main transoms to provide extra support for boards. In Canada this style is referred to as “English”. “American” has the transoms attached to the standards and is used less but has certain advantages in some situations. Since scaffolding is a physical structure, it is possible to go in and come out of scaffolding.

As well as the tubes at right angles there are cross braces to increase rigidity, these are placed diagonally from ledger to ledger, next to the standards to which they are fitted. If the braces are fitted to the ledgers they are called ledger braces. To limit sway a facade brace is fitted to the face of the scaffold every 30 metres or so at an angle of 35°-55° running right from the base to the top of the scaffold and fixed at every level.

Of the couplers previously mentioned, right-angle couplers join ledgers or transoms to standards, putlog or single couplers join board bearing transoms to ledgers - Non-board bearing transoms should be fixed using a right-angle coupler. Swivel couplers are to connect tubes at any other angle. The actual joints are staggered to avoid occurring at the same level in neighbouring standards.

The spacing of the basic elements in the scaffold are fairly standard. For a general purpose scaffold the maximum bay length is 2.1 m, for heavier work the bay size is reduced to 2m or even 1.8 m while for inspection a bay width of up to 2.7 m is allowed.

The scaffolding width is determined by the width of the boards, the minimum width allowed is 600 mm but a more typical four-board scaffold would be 870 mm wide from standard to standard. More heavy-duty scaffolding can require 5, 6 or even up to 8 board width. Often an inside board is added to reduce the gap between the inner standard and the structure.


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The lift height, the spacing between ledgers, is 2 m, although the base lift can be up to 2.7 m. The diagram above also shows a kicker lift, which is just 150 mm or so above the ground.

Transom spacing is determined by the thickness of the boards supported, 38 mm boards require a transom spacing of no more than 1.2 m while a 50 mm board can stand a transom spacing of 2.6 m and 63 mm boards can have a maximum span of 3.25 m. The minimum overhang for all boards is 50 mm and the maximum overhang is no more than 4x the thickness of the board.

Foundations

Good foundations are essential. Often scaffold frameworks will require more than simple base plates to safely carry and spread the load. Scaffolding can be used without base plates on concrete or similar hard surfaces, although base plates are always recommended. For surfaces like pavements or tarmac base plates are necessary.

Scaffolding showing required protection of a working platform with

maximum dimensions. Butt-board not visible. No couplers shown

For softer or more doubtful surfaces sole boards must be used, beneath a single standard a sole board should be at least 1,000 cm² with no dimension less than 220 mm, the thickness must be at least 35 mm. For heavier duty scaffold much more substantial baulks set in concrete can be required. On uneven ground steps must be cut for the base plates, a minimum step size of around 450 mm is recommended. A working platform requires certain other elements to be safe. They must be close-boarded, have double guard rails and toe and stop boards. Safe and secure access must also be provided.

Ties

Scaffolds are only rarely independent structures. To provide stability for a scaffolding framework ties are generally fixed to the adjacent building/fabric/steelwork.

General practice is to attach a tie every 4m on alternate lifts (traditional scaffolding). Prefabricated System scaffolds require structural connections at all frames

- ie.2-3m centres (tie patterns must be provided by the System manufacturer/supplier). The ties are coupled to the scaffold as close to the junction of standard and ledger (node point) as possible. Due to recent regulation changes, scaffolding ties must support +/- loads (tie/butt loads) and lateral (shear) loads.

Due to the different nature of structures there is a variety of different ties to take advantage of the opportunities.

Through ties are put through structure openings such as windows. A vertical inside tube crossing the opening is attached to the scaffold by a transom and a crossing horizontal tube on the outside called a bridle tube. The gaps between the tubes and the structure surfaces are packed or wedged with timber sections to ensure a solid fit.

Box ties are used to attach the scaffold to suitable pillars or comparable features. Two additional transoms are put across from the lift on each side of the feature and are joined on both sides with shorter tubes called tie tubes. When a complete box tie is impossible an l-shaped lip tie can be used to hook the scaffold to the structure, to limit inward movement an additional transom, a butt transom, is place hard against the outside face of the structure.

Sometimes it is possible to use anchor ties (also called bolt ties), these are ties fitted into holes drilled in the structure. A common type is a ring bolt with an expanding wedge which is then tied to a node point.

The least ‘invasive’ tie is a reveal tie. These use an opening in the structure but use a tube wedged horizontally in the opening. The reveal tube is usually held in place by a reveal screw pin (an adjustable threaded bar) and protective packing at either end. A transom tie tube links the reveal tube to the scaffold. Reveal ties are not well regarded, they rely solely on friction and need regular checking so it is not recommended that more than half of all ties be reveal ties.


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If it is not possible to use a safe number of ties rakers can be used. These are single tubes attached to a ledger extending out from the scaffold at an angle of less than 75° and securely founded. A transom at the base then completes a triangle back to the base of the main scaffold.

Specialty Scaffolding

Types of scaffolding covered by the Occupational Health and Safety Administration in the United States include the following categories: Pole; tube and coupler; fabricated frame (tubular welded frame scaffolds); plasterers’, decorators’, and large area scaffolds; bricklayers’ (pipe); horse; form scaffolds and carpenters’ bracket scaffolds; roof brackets; outrigger; pump jacks; ladder jacks; window jacks; crawling boards (chicken ladders); step, platform, and trestle ladder scaffolds; single-point adjustable suspension; two-point adjustable suspension (swing stages); multipoint adjustable suspension; stone setters’ multipoint adjustable suspension scaffolds, and masons’ multipoint adjustable suspension scaffolds; catenary; float (ship); interior hung; needle beam; multilevel suspended; mobile; repair bracket scaffolds; and stilts.

FormworkFormwork is the term given to either temporary or

permanent moulds into which concrete or similar materials are poured. In the context of concrete construction, the false work supports the shuttering moulds.

Formwork and concrete form types

Formwork comes in several types:

- Traditional timber formwork. The formwork is built on site out of timber and plywood or moisture-resistant particleboard. It is easy to produce but time-consuming for larger structures, and the plywood facing has a relatively short lifespan.

Timber formwork for a concrete column

It is still used extensively where the labour costs are lower than the costs for procuring reusable formwork. It is also the most flexible type of formwork, so even where other systems are in use, complicated sections may use it.

- Engineered Formwork System. This formwork is built out of prefabricated modules with a metal frame (usually steel oraluminium) and covered on the application (concrete) side with material having the wanted surface structure (steel, aluminium, timber, etc.). The two major advantages of formwork systems, compared to traditional timber formwork, are speed of construction (modular systems pin, clip, or screw together quickly) and lower life-cycle costs (barring major force, the frame is almost indestructible, while the covering if made of wood; may have to be replaced after a few - or a few dozen - uses, but if the covering is made with steel or aluminium the form can achieve up to two thousand uses depending on care and the applications).

Modular steel frame formwork for a foundation

- Re-usable plastic formwork. These interlocking and modular systems are used to build widely variable, but relatively simple, concrete structures. The panels are lightweight and very robust. They are especially suited for low-cost, mass housing schemes.

Re-usable plastic-formwork for mass housing irs


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- Permanent Insulated Formwork. This formwork is assembled on site, usually out of insulating concrete forms (ICF). The formwork stays in place after the concrete has cured, and may provide advantages in terms of speed, strength, superior thermal and acoustic insulation, space to run utilities within the EPS layer, and integrated furring strip for cladding finishes.

- “Coffor” is a structural stay-in-place formwork system to build constructions in concrete. It is composed of two filtering grids reinforced by vertical stiffeners and linked by articulated connectors that can be folded for transport. A standard panel 1.10 m x 2.70 m (3’ 8 x 9) weighs 32.7 kg and can be carried by hand or by any means of machine. After Coffor is placed, concrete is poured between the grids: excess water of concrete is eliminated by gravity and air is also eliminated. Coffor remains in the construction after concrete is poured and acts as reinforcement. Any type of construction can be built with Coffor: individual houses, multi-story buildings including high-rise buildings, industrial, commercial or administrative buildings. Several types of civil works can be done with Coffor. Coffor is delivered completely assembled from the factory. No assembly is necessary on the construction site.

Sketch of the side view of traditional timber formwork used to form

a flight of stairs

- Stay-In-Place structural formwork systems. This formwork is assembled on site, usually out of prefabricated fibre-reinforced plastic forms.

Placing a formwork component

These are in the shape of hollow tubes, and are usually used for columns and piers. The formwork stays in place after the concrete has cured and acts as axial and shear reinforcement, as well as serving to confine the concrete and prevent against environmental effects, such as corrosion and freeze-thaw cycles.

- Flexible formwork. In contrast to the rigid moulds described above, flexible formwork is a system that uses lightweight, high strength sheets of fabric to take advantage of the fluidity of concrete and create highly optimised, architecturally interesting, building forms. Using flexible formwork it is possible to cast optimised structures that use significantly less concrete than an equivalent strength prismatic section, thereby offering the potential for significant embodied energy savings in new concrete structures.

Slab Formwork (deck formwork)Some of the earliest examples of concrete slabs were

built by Roman engineers. Because concrete is quite strong in resisting compressive loads, but has relatively poor tensile or torsional strength, these early structures consisted of arches, vaults and domes. The most notable concrete structure from this period is the Pantheon in Rome. To mould this structure, temporary scaffolding and formwork or false work was built in the future shape of the structure. These building techniques were not isolated to pouring concrete, but were and are widely used in masonry. Because of the complexity and the limited production capacity of the building material, concrete’s rise as a favoured building material did not occur until the invention of Portland cement (and developments by the Edison Portland Cement Company) and reinforced concrete.

Timber beam slab formwork

Similar to the traditional method, but stringers and joist are replaced with engineered wood beams and supports are replaced with metal props. This makes this method more systematic and reusable.

Pantheon dome


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Traditional slab formwork

Schematic sketch of traditional formwork

On the dawn of the rival of concrete in slab structures, building techniques for the temporary structures were derived again from masonry and carpentry. The traditional slab formwork technique consists of supports out of lumber or young tree trunks that support rows of stringers assembled roughly 3 to 6 feet or 1 to 2 metres apart, depending on thickness of slab. Between these stringers, joists are positioned roughly 30 centimetres apart upon which boards or plywood are placed. The stringers and joists are usually 4 by 4 inch or 4 by 6 inch lumber. The most common imperial plywood thickness is ¾ inch and the most common metric thickness is 18 mm.

Metal beam slab formwork

Similar to the traditional method, but stringers and joist are replaced with aluminium forming systems or steel beams and supports are replaced with metal props. This also makes this method more systematic and reusable. Aluminium beams are fabricated as telescoping units, which allows them to span supports that are located at varying distances apart. Telescoping aluminium beams can be used and reused in the construction of structures of varying size.

Modular slab formwork

These systems consist of prefabricated timber, steel or aluminium beams and formwork modules. Modules are often no larger than 3 to 6 feet or 1 to 2 metres in size. The beams and formwork are typically set by hand and pinned, clipped, or screwed together. The advantages of a modular system are: this does not require a crane to place the formwork, faster construction with unskilled labour, formwork modules can be removed after concrete sets leaving only beams in place prior to achieving design strength.

Table or flying form systems

These systems consist of slab formwork “tables” that are reused on multiple stories of a building without being dismantled. The assembled sections are either lifted per elevator or “flown” by crane from one story to the next. Once in position the gaps between the tables or table and wall are filled with “fillers”. They vary in shape and size as well as their building material. The use of these systems can greatly reduce the time and manual labour involved in setting and striking the formwork. Their advantages are best utilized by large area and simple structures. It is also common for architects and engineers to design building around one of these systems.

Structure: A table is built pretty much the same way as a beam formwork but the single parts of this system are connected together in a way that makes them transportable. The most common sheathing is plywood, but steel and fiberglass are also in use. The joists are either made from timber, wood I-beams, aluminium or steel. The stringers are sometimes made of wood I-beams but usually from steel channels. These are fastened together (screwed, weld or bolted) to become a “deck”. These decks are usually rectangular but can also be other shapes.

Modular formwork with deck for housing project in Chile

Steel and plywood formwork for poured in place concrete

foundation

Traditional timber formwork on a jetty in Bangkok


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Support: All support systems have to be height adjustable to allow the formwork to be placed at the correct height and to be removed after the concrete is cured. Normally adjustable metal props similar to (or the same as) those used by beam slab formwork are used to support these systems. Some systems combine stringers and supports into steel or aluminium trusses. Yet other systems use metal frame shoring towers, which the decks are attached to. Another common method is to attach the formwork decks to previously cast walls or columns, thus eradicating the use of vertical props altogether. In this method, adjustable support shoes are bolted through holes (sometimes tie holes) or attached to cast anchors.

Size: The size of these tables can vary from 70 to 1,500 square feet (6.5 to 139.4 m2). There are two general approaches in this system:

1. Crane Handled: this approach consists of assembling or producing the tables with a large formwork area that can only be moved up a level by crane. Typical widths can be 15, 18 or 20 ft. or 5 to 7 metres but their width can be limited, so that it is possible to transport them assembled, without having to pay for an oversize load. The length might vary and can be up to 100 ft. (or more) depending on the crane capacity. After the concrete is cured, the decks are lowered and moved with rollers or trolleys to the edge of the building. From then on the protruding side of the table is lifted by crane while the rest of the table is rolled out of the building. After the centre of gravity is outside of the building the table is attached to another crane and flown to the next level or position.

Hand setting modular aluminium deck formwork

This technique is fairly common in the United States and East Asian countries. The advantages of this approach are the further reduction of manual labour time and cost per unit area of slab and a simple and systematic building technique. The disadvantages of this approach are the

necessary high lifting capacity of building site cranes, additional expensive crane time, higher material costs and little flexibility.

2. Crane fork or elevator handled: By this approach the tables are limited in size and weight. Typical widths are between 6 and 10 ft or 2 and 3 metres, typical lengths are between 12 and 20 ft or 4 and 7 metres, though table sizes may vary in size and form. The major distinction of this approach is that the tables are lifted either with a crane transport fork or by material platform elevators attached to the side of the building. They are usually transported horizontally to the elevator or crane lifting platform single handedly with shifting trolleys depending on their size and construction. Final positioning adjustments can be made by trolley.

This technique enjoys popularity in the US, Europe and generally in high labour cost countries. The advantages of this approach in comparison to beam formwork or modular formwork is a further reduction of labour time and cost. Smaller tables are generally easier to customize around geometrically complicated buildings, (round or non-rectangular) or to form around columns in comparison to their large counterparts. The disadvantages of this approach are the higher material costs and increased crane time (if lifted with crane fork).

Tunnel FormsTunnel forms are large, room size forms that allows

walls and floors to be cast in a single pour. With multiple forms, the entire floor of a building can be done in a single pour. Tunnel forms require sufficient space exterior to the building for the entire form to be slipped out and hoisted up to the next level. A section of the walls is left uncasted to remove the forms. Typically castings are done with a frequency of 4 days. Tunnel forms are most suited for buildings that have the same or similar cells to allow re-use of the forms within the floor and from one floor to the next, in regions which have high labour prices.

Flexible FormworkThere is an increasing focus on sustainability in design,

backed up by carbon dioxide emissions reduction targets. The low embodied energy of concrete by volume is offset by its rate of consumption which make the manufacture of cement accountable for some 5% of global CO2 emissions.

Concrete is a fluid that offers the opportunity to economically create structures of almost any geometry - we can pour concrete into a mould of almost any shape.


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This fluidity is seldom utilised, with concrete instead being poured into rigid moulds to create high material use structures with large carbon footprints. The ubiquitous use of orthogonal moulds as concrete formwork has resulted in a well-established vocabulary of prismatic forms for concrete structures, yet such rigid formwork systems must resist considerable pressures and consume significant amounts of material. Moreover, the resulting member requires more material and has a greater self-weight than one cast with a variable cross section.

Handset modular aluminium formwork

Simple optimisation methods may be used to design a variable cross section member in which the flexural and shear capacity at any point along the element length reflects the requirements of the loading envelope applied to it.

By replacing conventional moulds with a flexible system composed primarily of low cost fabric sheets, flexible formwork takes advantage of the fluidity of concrete to create highly optimised, architecturally interesting, building forms. Significant material savings can be achieved. The optimised section provides ultimate limit state capacity while reducing embodied carbon, thus improving the life cycle performance of the entire structure.

Control of the flexibly formed beam cross section is key to achieving low-material use design. The basic assumption is that a sheet of flexible, permeable fabric is

held in a system of false work before reinforcement and concrete are added. By varying the geometry of the fabric mould with distance along the beam, the optimised shape is created. Flexible formwork therefore has the potential to facilitate the change in design and construction philosophy that will be required for a move towards a less material intensive, more sustainable, construction industry.

Formwork tables in use at a building site with more complicated

structural features

Climbing FormworkClimbing formwork is a special type of formwork for

vertical concrete structures that rises with the building process. While relatively complicated and costly, it can be an effective solution for buildings that are either very repetitive in form (such as towers or skyscrapers) or that require a seamless wall structure (using gliding formwork, a special type of climbing formwork).

Various types of climbing formwork exist, which are either relocated from time to time, or can even move on their own (usually on hydraulic jacks, required for self-climbing and gliding formworks).

• Climbing formwork (crane-climbing): In this type of climbing formwork, the formwork around the structure is displaced upwards with the help of one or more cranes once the hardening of the concrete has proceeded far enough. This may entail lifting the whole section, or be achieved segmentally.

• Climbing formwork (self-climbing): In this type of formwork, the structure elevates itself with the help of mechanic leverage equipment (usually hydraulic). To do this, it is usually fixed to sacrificial cones or rails emplaced in the previously cast concrete.

Flying formwork tables with aluminiumand timber joists.


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• Gliding formwork: This type of formwork is similar to the self-climbing type above. However, the climbing process is continuous instead of intermittent, and is usually only interrupted for a very short time (for example to fix the mounting mechanisms to new anchoring points). The advantage is that it will produce seamless structures, but it requires a continuous, uninterrupted process throughout, with serious potential quality and stability problems if the pour has to be stopped.

Usage of FormworkFor removable forms, once the concrete has been poured

into formwork and has set (or cured), the formwork is struck or stripped (removed) to expose the finished concrete. The time between pouring and formwork stripping depends on the job specifications, the cure required, and whether the form is supporting any weight, but is usually at least 24 hours after the pour is completed. For example, the California Department of Transportation requires the forms to be in place for 1–7 days after pouring, while the Washington State Department of Transportation requires the forms to stay in place for 3 days with a damp blanket on the outside.

Spectacular accidents have occurred when the forms were either removed too soon or had been under-designed to carry the load imposed by the weight of the uncured concrete. Less critical and much more common (though no less embarrassing and often costly) are those cases in which under-designed formwork bends or breaks during the filling process (especially if filled with a high-pressure concrete pump). This then results in fresh concrete escaping out of the formwork in a form blowout, often in large quantities.

Concrete exerts less pressure against the forms as it hardens, so forms are usually designed to withstand a number of feet per hour of pour rate to give the concrete at the bottom time to firm up. For example, wall or column forms are commonly designed for a pour rate between 4–8 ft/hr. The hardening is an asymptotic process, meaning that most of the final strength will be achieved after a short time, though some further hardening can occur depending on the cement type and admixtures.

Wet concrete also applies hydrostatic pressure to formwork. The pressure at the bottom of the form is therefore greater than at the top.

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