Post-Earthquake Rapid Visual Damage Assessment of · PDF file · 2017-03-28initiated research study to contribute towards informed ... 3Analysis of public buildings and high-rise

Tribhuvan University

Institute of Engineering

South Asia Urban Knowledge Hub – Nepal

ADB Project Number: 46465

Regional - Capacity Development Technical Assistance (R-CDTA)

Urban Knowledge Hub Knowledge Products No. 1 and 2 (Single Report)

Post-Earthquake Rapid Visual Damage Assessment of Public and High-Rise Buildings in Kathmandu Valley, Nepal

Documentation, Analysis, and Policy Implication

June 2016

Post-Earthquake Damage Assessment of Public and High-Rise Buildings in Kathmandu Valley, Nepal: Documentation, Analysis, and Policy Implications

South Asia Urban Knowledge Hub – Nepal, Institute of Engineering ii

STUDY TEAM

Sudha Shrestha, Prof., PhD Team Coordinator

Kirti Kusum Joshi, PhD Urban Specialist

Iswar Man Amatya, Assoc. Prof. Infrastructure Specialist

Ashim Bajracharya GIS Specialist

Luna Bajracharya Nisha Shrestha Research Assistants

Rakesh Maharjan Research Student Assistant

Roshan Thapa Magar Gaurav Nepal Kiran KC Roshan Pradhan Interns

Tribhuvan University

Institute of Engineering South Asia Urban Knowledge Hub Nepal

Acknowledgements. Prof. Dr. Tri Ratna Bajracharya (Dean, Institute of Engineering), Padma K. Mainalee (Under-Secretary, Ministry of Urban Development), Keiichi Tamaki (Senior Urban Development Specialist, ADB), Vivian Castro-Wooldridge (Urban Development Specialist, ADB Nepal Resident Mission), and Michelle Laurie (Knowledge Management Specialist/ ADB Consultant).

Established in 2014, the South Asia Urban Knowledge Hub ("the K-Hub") is a regional initiative aimed at improving policy making in urban sector based on evidence-based research. The K-Hub initiative is supported by the Asian Development Bank (ADB) and the respective governments of India, Bangladesh,

Nepal, and Sri Lanka. The initiative is also being supported by the Bill and Melinda Gates Foundation (BMGF) particularly for innovative on-site sanitation as part of the Sanitation Financing Partnership Trust Fund created by ADB and BMGF. Each participating country has a national center endorsed by the respective government: National Institute of Urban Affairs (NIUA) in India, International Training Network Centre – Bangladesh University of Engineering and Technology (ITN-BUET) in Bangladesh, Tribhuvan University – Institute of Engineering in Nepal, and University of Moratuwa in Sri Lanka. The regional center of the K-Hub is based at the NIUA in India. http://khub.niua.org/

Cover Photo (K. K. Joshi): A high-rise residential building with post-earthquake damage in Lalitpur district

http://khub.niua.org/


South Asia Urban Knowledge Hub – Nepal, Institute of Engineering iii

CONTENTS

ACRONYMS & ABBREVIATIONS ..................................................................................................... v I. BACKGROUND ......................................................................................................................... 1 II. RAPID VISUAL DAMAGE ASSESSMENT: TECHNIQUE AND APPLICATION ....................... 2 2.1 Technique .................................................................................................................................. 2 2.2 Application of RVDA Results: A Literature Review.................................................................... 4 III. METHODOLOGY OF THE STUDY ........................................................................................... 5 3.1 Data Collection .......................................................................................................................... 5 3.2 Technique for Analysis .............................................................................................................. 6 3.3 Dissemination of Preliminary Results ........................................................................................ 7 3.4 Scope and Limitation of the Study ............................................................................................. 7 IV. Results and Discussions .......................................................................................................... 11 4.1 Owner-Built Residential Buildings ........................................................................................... 11 4.2 Government Office Buildings ................................................................................................... 20 4.3 Public Hospital Buildings ......................................................................................................... 24 4.4 Public Academic Buildings ....................................................................................................... 26 4.5 High-Rise Apartment Buildings ................................................................................................ 30 V. POLICY IMPLICATIONS ......................................................................................................... 33 VI. CONCLUSION ......................................................................................................................... 37 REFERENCES ................................................................................................................................ 38 ANNEX Map 1: Location of all buildings assessed ......................................................................................... 9 Map 2: Catchment area and population of all select buildings assessed ........................................ 10 Map 3: Damage rating of government office buildings assessed .................................................... 22 Map 4: Damage rating of hospital buildings assessed .................................................................... 25 Map 5: Damage rating of academic buildings assessed ................................................................. 27 Map 6: Damage rating of high-rise buildings assessed ................................................................... 32 Figure 1: Standard damage assessment placards ............................................................................ 3 Figure 2: Mechanism of soil liquefaction ............................................................................................ 7 Figure 3: Pounding during an earthquake between buildings of unequal heights (left); buildings separated by sufficient gap (right) ................................................................................................... 16 Figure 4: Typical process of incremental building construction (top), and corresponding hypothetical fragility curves (bottom) ............................................................................................... 18 Figure 5: Damage rating vs. liquefaction potential for government office buildings ........................ 20 Figure 6: Catchment population of select government office buildings assessed ........................... 23 Figure 7: Damage rating vs. liquefaction potential for hospital buildings ........................................ 24 Figure 8: Catchment population of select hospital buildings assessed ........................................... 26 Figure 9: Damage rating vs. liquefaction potential for government office buildings ........................ 28 Figure 10: Catchment population of select academic buildings assessed ...................................... 28 Figure 11: Cumulative count of select academic buildings versus damage rating .......................... 30 Figure 12: Damage rating vs. liquefaction potential for government office buildings ...................... 31 Figure 13: The way forward ............................................................................................................. 33 Table 1: Posting Classification ........................................................................................................... 2 Table 2: Deficiencies and associated damages in URM buildings .................................................. 11 Table 3: Deficiencies and associated damages in RCC buildings .................................................. 13 Table 4: Deficiencies and associated damages common in both UBM and RCC buildings ........... 16 Table 5: Damage rating vs. liquefaction potential for government office buildings ......................... 20 Table 6: Damage rating vs. liquefaction potential for public hospital buildings ............................... 24 Table 7: Damage rating vs. liquefaction potential for public academic buildings ............................ 26 Table 8: Damage rating vs. age of select public academic buildings .............................................. 29 Table 9: Damage rating vs. liquefaction potential for high-rise residential buildings ....................... 30 Table 10: Key issues, concerns, and recommended actions .......................................................... 34


South Asia Urban Knowledge Hub – Nepal, Institute of Engineering iv

Plate 1: Red and green placards (non-standard) placed on school buildings in Kavre ..................... 3 Plate 2: Presentation by the study team at a seminar organized by NAST ....................................... 7 Plate 3: Typical construction- and structural deficiencies observed in the URM buildings in the 2015 earthquakes ............................................................................................................................ 12 Plate 4: Typical construction- and structural deficiencies observed in the RCC buildings in the 2015 earthquakes ..................................................................................................................................... 15 Plate 5: Typical construction- and structural deficiencies observed in both URM and RCC buildings in the 2015 earthquakes .................................................................................................................. 18 Plate 6: Park View Apartment in Dhapasi, Kathmandu after the earthquake .................................. 31


South Asia Urban Knowledge Hub – Nepal, Institute of Engineering v

ACRONYMS & ABBREVIATIONS

ADB Asian Development Bank

ATC Applied Technology Council

DMG Department of Mines and Geology

DUDBC Department of Urban Development and Building Construction

GDP Gross domestic product

GSDMA Gujarat State Disaster Management Authority

IOE Institute of Engineering

K-Hub Knowledge Hub

KVDA Kathmandu Valley Development Authority

MOFALD Ministry of Federal Affairs and Local Development

MOHA Ministry of Home Affairs

MOUD Ministry of Urban Development

MW Moment magnitude

NAST Nepal Academy of Science and Technology

NBC National Building Code

NEA Nepal Engineers‟ Association

NEC Nepal Engineering College

NRA Nepal Reconstruction Authority

NPC National Planning Commission

NSET Nepal Society for Earthquake Technology

PDNA Post-Disaster Needs Assessment

RCC Reinforced cement concrete

RVDA Rapid visual damage assessment

SLTDC Shelter and Local Technology Development Center

SONA Society of Nepalese Architects

TU Tribhuvan University

URM Unreinforced masonry


South Asia Urban Knowledge Hub – Nepal, Institute of Engineering 1

I. BACKGROUND

The April-May 2015 earthquakes caused huge loss of lives and properties in Nepal, 1 resulting into about 9,000 casualties and 22,300 injuries. About 8 million people (one-third of the national population) were directly affected. Over half a million houses collapsed. The gross domestic product (GDP) dropped by over 1.5 percentage points (NPC, 2015). Although the most affected regions were rural areas outside the Kathmandu Valley, the latter also witnessed about 1,700 casualties, 13,000 injuries, and over 0.7 million collapsed houses.2

In light of the destruction caused by the earthquakes, the Urban Knowledge Hub (K-Hub) initiative in Nepal – based at the Institute of Engineering (IOE) and supported by the Asian Development Bank (ADB) and the Ministry of Urban Development (MOUD) – initiated research study to contribute towards informed policymaking on risk-resilient urban development through the development and promotion of knowledge products.

Urban resilience is a city‟s ability to withstand and recover from unexpected shocks associated with natural hazards such as earthquakes (ADB, 2013). Building urban resilience begins with the collection, management, and dissemination of information on damage and prevailing risks. This is the focus of the first K-Hub objective as stated below:

Objective: Improve urban development policies to mitigate prevailing earthquake risks in Kathmandu Valley by engaging decision makers with credible information and analysis on building-sector damage in the Valley due to the April-May 2015 earthquakes.

Soon after the April 25, 2015 Earthquake, the Institute of Engineering (IOE) trained engineers on the rapid visual damage assessment (RVDA) technique. Nepal Engineers‟ Association (NEA) expanded upon this at a larger scale, and mobilized hundreds of volunteer engineers for the fieldwork targeting residential buildings as per the request of homeowners, focusing primarily in the Kathmandu Valley urban areas.

The MOUD and its policy unit Department of Urban Development and Building Construction (DUDBC) assessed government buildings, high-rise apartments, and organized housing colonies. Likewise, different other agencies and groups conducted RVDAs of buildings of their interest. For instance, the IOE assessed buildings of public academic institutions. The Department of Education evaluated safety of school buildings.

The objective of RVDA is to evaluate damage sustained by buildings, and thereby to ascertain safety level for the continued use of the buildings. By creating public awareness to avoid risky buildings, the RVDAs are thought to have saved many lives in the Kathmandu Valley when the second powerful earthquake hit the country on May 12, 2015.

Under the first K-Hub objective, this report presents results of post-earthquake RVDA of buildings in Kathmandu Valley with documentation and analysis (Knowledge Product 1), and identification of prevailing risks and policy implications (Knowledge Product 2).3

1The country was hit by 7.8 MW earthquake on April 25, 2015 and by 7.3 MW earthquake on May 12, 2015.

2Preliminary report prepared by the Ministry of Home Affairs (MOHA) available at http://drrportal.gov.np/

uploads/document/175.pdf. 3Analysis of public buildings and high-rise buildings are based on primary data in case of residential buildings,

secondary information is referred to.



II. RAPID VISUAL DAMAGE ASSESSMENT: TECHNIQUE AND APPLICATION

2.1 Technique

The post-earthquake rapid evaluation procedure assumes that a competent engineer can assess damages, at least partially, through visual inspection augmented by investigative tests, structural analysis, and knowledge of the building construction (MOUD, 2011). By determining how the structural damage has changed structural properties, it is feasible to develop performance restoration measures that, if implemented, would restore the damaged building to a condition such that its future earthquake performance would be essentially equivalent to that of the building in its pre-event condition.

The RVDA procedure is based on ATC-20 (Post-Earthquake Safety Evaluation of Buildings), prepared by Applied Technology Council (ATC),4 which explains procedures for evaluating earthquake-damaged buildings, and assessing the overall risk from the damage, recommending which of the three placards – green, yellow, or red – should be posted on the building. The RVDA involves ranking buildings as INSPECTED (apparently safe, green placard), LIMITED ENTRY (yellow placard), or UNSAFE (red placard) (see Figure 1) with the following implications (see also Table 1):

INSPECTED: Observed damage, if any, does not appear to pose a safety risk; vertical or lateral capacity not significantly decreased; repairs may be required; lawful entry, occupancy and use permitted

LIMITED ENTRY: Some risk from damage in all or part of building; restriction in terms of duration of occupancy and/or areas of occupancy and/or usage

UNSAFE: Falling, collapse, or other hazard; does not necessarily indicate that demolition is required; owner must mitigate hazards to satisfaction of jurisdiction to gain entry.

Table 1: Posting Classification

Posting Classification

Color Description

INSPECTED Green

No apparent hazard found, although repairs may be required. Original lateral load capacity not significantly decreased. No restriction on use or occupancy

LIMITED ENTRY

Yellow

Dangerous condition believed to be present. Entry by owner permitted only for emergency purposes and only at own risk. No usage on continuous basis. Entry by public not permitted. Possible major aftershock hazard.

UNSAFE

Red

Extreme hazard, may collapse. Imminent danger of collapse from an aftershock. Unsafe for occupancy or entry, except by authorities.

Source: Adapted from MOUD (2011).

The rapid evaluation is carried out just after the earthquake for the purpose of safety evaluation of the buildings so that people can decide whether or not to occupy the buildings following an earthquake. The results from RVDA are not intended to be used for demolition as many buildings assigned as UNSAFE might be possible to restore and retrofit.

4https://www.atcouncil.org.



Although an RVDA has its own limitations due to short inspection time (30 minutes or less), it provides quick information on „what-went-wrong‟ side of urban planning and development. The RVDA method is also useful in identifying and mitigating persistent risks, which, if left unaddressed, may prove to be costly in the event of future earthquakes.

Figure 1: Standard damage assessment placards

Source: https://www.atcouncil.org/products/downloadable-products/placards (with color added)

For rapid evaluation following the 2015 Earthquakes, standard ATC-approved placards could not be used widely. Instead color stickers were used along with the government approved form presented in Annex A.

Plate 1: Red and green placards (non-standard) placed on school buildings in Kavre



Photo credit: M. Thapa

2.2 Application of RVDA Results: A Literature Review

RVDA provides quick results on the vulnerability of buildings in the aftermath of a large earthquake. Seismic vulnerability is the probability of a building to suffer a certain level of damage when subjected to a seismic event of defined intensity (Lang & Bachmann, 2003). In other words, vulnerability is a measure of reduction in the building's structural efficiency due to seismic shocks, and thereby an indication of the building's residual ability to ensure expected use under normal post-earthquake conditions (Vicente, Parodi, Lagomarsino, Varum, & Silva, 2011). Observation of past damages following earthquakes is often the sole way to predict the likely performance of buildings in future earthquakes (Karababa & Pomonis, 2011).

Damage assessment also helps in revealing the level of vulnerability of certain types of buildings or the dominant types of construction vis-à-vis all other building typologies (Karababa & Pomonis, 2011). This helps formulate reconstruction strategies. For instance, most traditional buildings were heavily damaged in the 2015 earthquake. The reason behind the level of destruction witnessed by such buildings needs serious investigation but RVDAs helped initiate discussions on the future of these buildings. 5 Several measures ranging from retrofitting to house-pooling are being discussed.

RVDA can also serve as the pre-stage of the more comprehensive detailed evaluation of damaged buildings – rapid assessment helps in formulating proper short-term post-earthquake strategies in which post-aftershock usability of the existing buildings is the main concern whereas detailed assessment contribute to long term reconstruction strategies (Korkmaz, 2009).

During strong earthquakes, some structural damage is expected to occur in any type of buildings. The primary concern is to prevent fatal damage from earthquakes. Although after each earthquake disaster, seismic design codes may get improved, old buildings would be left unprotected, and thereby remain vulnerable (Otani, 2000). Post-earthquake damage assessment also helps in identifying buildings for gradual removal or retrofitting.

One of the most important applications of a post-earthquake assessment results is the refinement of seismic safety provisions. For instance, the 1968 Tokachi-oki Earthquake in Japan caused severe damage to reinforced concrete buildings, which led the government

5 The K-Hub Nepal has prepared a case study on the traditional buildings in Sankhu. The findings suggest

that traditional building construction techniques follow principles of seismic-resilient design but most of the damaged buildings lacked proper maintenance despite decades (or even over a century) of continued use.



to develop an integrated method to evaluate seismic vulnerability of existing buildings (Otani, 2000). There was a significant change in the seismic code in 1981.6

Even in Nepal, the National Building Code (NBC), 1994 was prepared to improve building design and construction methods, learning lessons from destruction caused by the 1988 Eastern Nepal earthquake that killed about 700 people. The NBC is being revised to incorporate lessons learnt from the 2015 earthquake. It is observed, at least in Kathmandu Valley, that most of the buildings that suffered severe damages did not comply even with the very basic provisions of the NBC.

Because of quick results at low cost, the RVDAs are widely used in several countries. In most cases, the RVDAs are guided by the ATC-20 family of documents as was the case in Nepal. Not all country-specific vernacular buildings as well as cultural and government contexts are addressed in the ATC-20 documents, which is understandable. Rodgers, et al. (2014) provides example of Bhutan on how local contexts can be integrated in the adaptation of ATC-20 guidelines.

Considering local contexts include promoting use of locally available materials and practices, which is very crucial from the perspective of housing affordability. Within 6 months of the devastating 2001 Bhuj earthquake in Kachchh district of Gujarat, India (deaths: over 13,000; damaged buildings: over 1 million), the Gujarat State Disaster Management Authority (GSDMA) released guidelines for earthquake-resistant construction using traditional wall materials followed guidelines for stabilized earthen wall buildings and quality control procedures, targeting the most commonly observed rural and peri-urban construction types in Kachchh (Hausler, 2004).

In the aftermath of the 2015 earthquakes in Nepal, several studies have documented types and causes of building failures (e.g., Surana, 2015; Wijeyewickrema, et al., 2015; Gautam, et al., 2016) using methods which seem to have become ubiquitous in these types of studies around the world (e.g., Jain, et al., 2002; Korkmaz, 2009; Karababa & Pomonis, 2011). As most of the building types, particularly in urban areas, are becoming more similar in terms of materials and construction technology, the types and causes of post-earthquake building damages documented in these studies are also comparable, and so are the lessons learnt.

III. METHODOLOGY OF THE STUDY

3.1 Data Collection

The study analyzes and summarizes results of the post-earthquake damage assessment of owner-built residential buildings, high-rise buildings and public academic and hospital buildings. In case of owner-built residential buildings, which dominate the housing stock in the Kathmandu Valley, the study uses secondary sources (e.g., Surana, 2015; Wijeyewickrema, et al., 2015; Gautam, et al., 2016) in the case of such buildings. Following four other types of buildings are analyzed using primary (raw) data: (1) government office buildings, (2) public academic buildings, (3) public hospital buildings, and (4) high-rise residential buildings. All of these are buildings of public interest.

The first three types of buildings are associated with public services, and are also buildings where large number of people gather. The last type of buildings considered is

6 Damage statistics show that in the 1995 Kobe earthquake, compared to pre-1981 construction, operational

damage in newer buildings was higher at 94.0% (79.4%) but heavy damage and collapse were respectively 4.0%(10.0%) and 2.1% (10.6%) where figures in the parenthesis correspond to pre-1981 construction (Otani, 2000).



different in terms of ownership; however, high-rise residential buildings are unique in the sense that these buildings consume huge resources for construction and are built to accommodate a large number of people. So the public welfare and concern are at stake.

The RVDA of government buildings, hospital buildings, and high-rise buildings was performed by the government agencies whereas evaluation teams mobilized by the IOE assessed public academic buildings (see Annex B for the list of buildings assessed).

3.2 Technique for Analysis

For analysis, buildings with RVDA data were located on vector layers in GIS platform using base maps sourced from OpenStreetMap (OSM)7 and Google Earth Image, with field visits conducted as needed in order to verify building locations. As aforementioned, analysis of residential buildings is based on previous studies.

The 2015 earthquakes provided opportunity for the practical implementation of the guidelines on post-disaster RVDA of buildings prepared, among others, by MOUD (2011). However, previous relevant studies including MOUD (2011) focus on the structural aspects of individual buildings, often neglecting site conditions. In this study, the following four parameters of analysis are considered in the case of buildings with primary data (the first two parameters are considered for the residential buildings with secondary data):

1. Structural factors: The main structural damages and causes are summarized.

2. Soil condition: Poor soil conditions predominant in the Kathmandu Valley continue to pose threat to the structures‟ performance and robustness against seismic shocks. In this study, liquefaction susceptibility of a location is considered as a proxy of weak soil condition (see Box 1). The location of assessed buildings overlaid on liquefaction zones is presented in Map 1.

3. Age of buildings: In Nepal, the building age is one of the most neglected factors vis-à-vis structural vulnerability. Once built, buildings are hardly replaced unless they completely collapse or owners decide to replace them. In this study, the age and damage rating of buildings are correlated to see the effect of ageing on buildings‟ performance in the 2015 earthquakes.

4. Catchment population: In case of strong earthquakes, it is common for people to gather in the nearby open spaces. However, because of increasing population density and haphazard urban growth in the Valley, open spaces are increasingly getting rarer with every passing year. In this study, public buildings with sizeable open spaces are identified, and their catchment areas are determined, assuming a walking distance of 1 km (or less in case of overlap with the catchment areas of other buildings) (Map 2; see also Table C5 in Annex C). In case of overlapped catchment areas, Thessian polygons are used to determine catchment area. The population (estimated for 2015 on the basis of 2011 data) within the Thessian polygon is treated as the catchment population for the building considered. The population for 2015 is estimated using annual exponential growth rate of 4.76% for Kathmandu district, 3.23% for Lalitpur district and 2.96% for Bhaktapur District.

Box 1: Soil liquefaction

Soil liquefaction is a phenomenon whereby saturated or partially saturated soil substantially

7 http://www.openstreetmap.org



loses strength and stiffness in response to earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid (Figure 2).

8 Liquefaction and related

phenomena have resulted into tremendous amounts of damage in earthquakes around the world including in the Kathmandu Valley. The geology of the Valley is characterized by unconsolidated and semi-consolidated sediments, making soil liquefaction a major risk during large earthquakes. In the 2015 earthquake, liquefaction was observed in different places in the Kathmandu Valley, causing a number of structures to settle and fail.

Figure 2: Mechanism of soil liquefaction

Source: http://www.cti.co.jp

3.3 Dissemination of Preliminary Results

The preliminary results of the study were presented at a seminar on Post-Earthquake Settlement Planning and Housing organized on March 24, 2016 by Nepal Academy of Science and Technology (NAST) in collaboration with Shelter and Local Technology Development Center (SLTDC). The program was organized to discuss on post-earthquake planning endeavors in the settlement and housing sector.

The presentation by the study team was followed by an interactive discussion with constructive feedback received from the participants which included, among others, officials from NAST, SLTDC, Department of Urban Development and Building Construction (DUDBC), Nepal Reconstruction Authority (NRA), Society of Nepalese Architects (SONA), UN- Habitat, Good Earth Nepal, and National Society for Earthquake Technology (NSET).

Plate 2: Presentation by the study team at a seminar organized by NAST

3.4 Scope and Limitation of the Study

The findings on owner-built residential buildings presented in this building are based on secondary information from previous studies. The information is mostly descriptive with photographic evidence as it is based on rapid visual assessment. On the other hand, the data on high-rise buildings and public hospital buildings has been provided by the

8 https://en.wikipedia.org/wiki/Soil_liquefaction.

http://www.cti.co.jp/



DUDBC whereas the data on public academic buildings has been collected by the field teams mobilized earlier by the IOE. Both datasets hitherto had not been analyzed to the extent done in this study.

The scope of this study is to add value to the existing knowledge by incorporating urban planning perspectives into the analysis of post-earthquake damage assessment of buildings within the limitation inherent in the secondary sources or raw datasets used in this study. For instance, this study does not provide information on the share of certain types of building failures vis-à-vis all other cases. Likewise, the study analyses available data on public buildings which were recorded; there were other such buildings which were not recorded at all. It is, therefore, important to note that the study of public buildings is based on a sample size.

One of the most significant types of buildings in the Kathmandu Valley is the traditional buildings which deserve separate study because of the unique construction technique used. This study does not address such buildings.9

9 A companion study on traditional buildings in Sankhu has been conducted by Nepal K-Hub.



Map 1: Location of all buildings assessed



Map 2: Catchment area and population of all select buildings assessed



IV. Results and Discussions

4.1 Owner-Built Residential Buildings

The 2015 earthquakes resulted into about 1,700 casualties, 13,000 injuries, and over 0.7 million collapsed houses in the Kathmandu Valley. Most of the damages happened due to the failure of owner-built residential buildings. The most common type of buildings in the Kathmandu Valley is the moment resisting frame structure with monolithic slab cast in beams and columns, resting on isolated footings, also called reinforced cement concrete (RCC) frame structure. However, until few decades ago, unreinforced masonry (URM) buildings – buildings with load-bearing wall made of sun-burnt or fired clay bricks – were more prevalent, and many such buildings still exist.

Because the Nepal National Building Code (NBC) was made mandatory only a decade ago – in 2005 – and that also in municipalities,10 the structural safety of many existing buildings in urban or urbanizing areas is of great concern. The extent and nature of damages sustained in the 2015 earthquake by many buildings reveal extremely poor construction technique and workmanship. The construction- and structural deficiencies and associated damages in (a) URM buildings, (b) RCC frame structure, and (c) both types are summarized in Table 2 and 3 respectively.

Table 2: Deficiencies and associated damages in URM buildings

Deficiencies Description 1. Structural integrity

Lack of any bands at various levels such as sill, lintel or gable

Out-of-plane collapse due to lack of proper bonding in the load bearing walls and due to lack of integration within the structural components

2. Binding materials Detachment of mud mortar used for binding brick units leading to delamination of wythes (observed in historic settlements)

3. Load path discontinuity

Incompatible addition (e.g., RCC elements on upper stories)

Reentrant corners and diaphragm discontinuities

Number of stories even up to six

Lack of struts to transfer loads from cantilevers and roofs to walls

4. Connections Poor connection between walls, walls and floor, and wall and roof, often leading to out-of-plane failures (on the other hand, use of timber structural elements functioned well against out-of-plane collapse of external walls)

Disregard to the traditional practices of tying up building elements using wooden pegs and bands

Sharing of walls, or sometimes no own wall, on one or both sides in row houses in traditional settlements

5. Age of buildings

Buildings up to or over 100 years in age (used by at least three generations) implying vulnerability even before the earthquake

Lack of proper repair, strengthening or retrofit despite years of continued use (although the same buildings survived past large earthquakes)

6. Foundation problem Foundation not constructed on levelled base

7. Heavy roofs

Use of roofing tiles with thick layers of mud mortar

Construction of RRC slab on ageing buildings

Roofing elements not properly tied or anchored with other structural members

Construction of gable portion with thick brick wall

8. Pounding and progressive failure

Row or attached masonry buildings with different heights and building components, causing walls to bulge out and fail during earthquakes

Source: Based on Gautam, et al. (2016); see also Surana (2015), and Wijeyewickrema et al., (2015). See Plate 1 for photographic evidence.

10

The Nepal NBC was first drafted in 1994 following the loss of 700 people in the 1988 M6.8 Eastern Nepal earthquake. Approved in 2003, the NBC became a legally binding document in all municipalities since 2005.



Plate 3: Typical construction- and structural deficiencies observed in the URM buildings in the 2015 earthquakes

(a) Out-of-plane collapse of load bearing

masonry wall in mud mortar in Bungamati (The

collapsed building had no proper wall of its

own on sides shared adjacent buildings) (Photo

credit: K K Joshi)

(b) Collapse of corner ends(Photo

credit:L.Bajracharya)

(c) Complete collapse of masonry building with

RCC slab (Gautam, et al., 2016)

(d) Heavy load concentration in the fourth story of

a masonry building (Gautam, et al., 2016)

(e) Collapse of mud mortar (Photo

credit: :L.Bajracharya)

(f) Out-of-plane failure of gable portion (Gautam,

et al., 2016)



g) Collapse of roof structure and masonary h) Collapse of masonary

wall (Photo credit: :L.Bajracharya) walls (Photo credit: :L.Bajracharya)

i) Collapse of corner walls (Photo j) Collapse of entire upper floor credit: :L.Bajracharya)

k) Pounding effect l) Collapse of entire upper floor



Table 3: Deficiencies and associated damages in RCC buildings

Deficiencies Description 1. Soft-story

11 Open floor layout with fewer infill walls for commercial purposes such as

stores and parking lots in majority of roadside RCC buildings, leading to increased displacement in the ground floor due to relative flexibility

Massive beams and smaller columns (‘‘weak column-strong beam’’) also frequently observed

2. Structural detailing

Compromise in the number and size of reinforcement bars, and large spacing between stirrups, leading to column failure

Poor connection between structural components (e.g., welding for connection of vertical reinforcements rather than anchoring, weak beam-column connection, and faulty layout and insufficient development length of reinforcement bars)

Plastic hinge formation along with concrete spall caused due to buckled re-bars on ground floor

Lack of reinforcement in infill walls (except in some apartments)

3. Infill wall deficiency Treatment of infill walls mostly as non-load-bearing partition walls only although during earthquakes, lateral loads can also get transferred to the infill walls because of the stiffness of the brick masonry walls, leading to diagonal cracks from horizontal shear and even to out-of-plane failure of the infill wall system

4. Floating column12

Lateral forces not transferred effectively to the foundation if transfer beams (girders) are not stiff enough, resulting into overturning forces that can cause columns in the ground floor to buckle, leading to severe damage

5. Concrete mixing and placement

Above permissible water cement ratio to achieving workability

Poor mixing and placement of concrete leading to segregation and bleeding

Poor workmanship

Corrosion of reinforcement bars due to insufficient clear cover

Use of round aggregates leading to poor stiffness, weak binding and out-of-plane failure.

6. Building asymmetry and slenderness

Asymmetry in terms of plan (layout) and/or elevation, adding vulnerability to earthquakes

Construction of irregularly-shaped buildings (e.g., triangular shaped) dictated by the shape of the lots

Inclination of owners of small plots to build slender buildings to offset space restriction posed by small plinth area, which are highly vulnerable to earthquake shocks, particularly to lateral shifts

Clear violation of building byelaws and NBC visible in case of many slender structures (In theory, the NBC restricts height-to-breadth and length-to-breadth ratio to less than 3)

7. Load accumulation in upper stories

Heavy construction on the upper floors leading to possible pan-cake failure

Reduced column size in upper floors despite higher load concentration

Installation of overhead water tanks and even telecommunication towers on top floor without any structural analysis

Source: Based on Gautam, et al. (2016); see also Surana (2015), and Wijeyewickrema et al., (2015). See Plate 2 1 for photographic evidence.

11

The soft-story phenomenon occurs when a lower level floor of a building is significantly weaker and more flexible than its upper floors

12 A floating column is a vertical element resting on a beam – a horizontal member – which in turn transfers load to other columns below it. Although floating columns are sometimes used as a part of architectural design, the common purpose in Nepal is to make more rooms on the upper floors on cantilevered slabs, i.e. beyond the structural system.



Plate 4: Typical construction- and structural deficiencies observed in the RCC buildings in the 2015 earthquakes

Lower two stories collapsed in this building in

Gongabu, Kathmandu due to soft-story effect

(Wijeyewickrema et al., 2015)

Soft story failure in a RCC frame building in Lubhu

(Surana, 2015)

Column failure due to large gap of stirrups

(Gautam, et al., 2016)

Floating columns and continued construction in

upper stories (Gautam, et al., 2016)

Failure at beam-column joint in Kantipur

Publication office, Kathmandu (Surana, 2015)

Slender structure in Kathmandu

(Photocredit: :L.Bajracharya)



Table 4: Deficiencies and associated damages common in both UBM and RCC buildings

Deficiencies and associated damages

Description

1. Pounding effects13

Construction of buildings without setback from adjacent buildings, leaving sufficient ground for pounding effect during earthquakes, which is particularly vulnerable in case of differences in building heights

2. Foundation design and soil condition

Improperly designed stepped foundation on sloped or terraced lands, leading to possible torsional failure of building

Construction of large buildings on river banks, fertile lands with weak bearing capacity, and liquefaction-prone areas without proper foundation design (The severely damaged areas of Sitapaila and Gongabu within Kathmandu Metropolitan City are high liquefaction-prone areas with soil bearing capacity of 52 and 106 KN/m

2 respectively. As per the NBC, these

sites correspond to weak to soft foundation types.)

3. Incremental construction

Non-monolithic structural system with inherent weakness due to phasewise construction caused by variation in quality of construction and materials

Source: Based on Gautam, et al. (2016); see also Surana (2015), and Wijeyewickrema et al., (2015). See Plate 3 1 for photographic evidence.

Common to both UGM and RCC buildings, the following three deficiencies need special attention:

1. Pounding effect: If buildings are built without sufficient gap and the interaction has not been considered, the buildings may pound each other during an earthquake. Building pounding can alter the dynamic response of both buildings, and impart additional inertial loads on both structures. Buildings that are of the same height and that have matching floors will exhibit similar dynamic behavior. In such case, when the buildings pound, floors will impact other floors, so damage due to pounding usually will be limited to non-structural components. But when the floors of adjacent buildings are at different elevations, floors will impact the columns of the adjacent building, which can cause structural damage.

Figure 3: Pounding during an earthquake between buildings of unequal heights (left); buildings separated by sufficient gap (right)

Source: MOUD (2011)

2. Soil condition and liquefaction: The more localized nature of damage during the 2015 Earthquakes verifies the effect of topographic amplification, ridge effect and local site effects. However, due to the lack of site specific design spectrum and localized design guidelines, construction practices tend to be similar across all locations regardless of the soil conditions.

13



Areas such as Gongabu and Dhapasi, where damages have been massive, were traditionally known as areas to avoid for building construction. For instance, in local (Newari) language, “bu” – as in Gongabu –means “rice field” but after the construction of bus-park, Gongabu became one of the fastest growing urban areas in the Valley.

Besides Gongabu and Balaju areas, liquefaction-induced damages were also observed in Bhaktapur whereby the buildings of Nepal Engineering College and of surrounding areas suffered relative settlements.

Because the Kathmandu valley deposits are composed mainly of saturated sand and clay layers with a shallow ground water table, liquefaction is highly anticipated. In the 2015 earthquakes, no liquefaction-induced damage to structures was found except in the case of the Nepal Engineering College (NEC) where buildings suffered subsidence. However, Okamura, et al. (2015) discovered occurrence of liquefaction in five areas, viz. Jharuwarashi, Bungamati, Imadol, Nepal Engineering College area, and Manamaiju. All these areas are in high or medium liquefaction susceptibility zone with the exception of Jharuwarashi area; fortunately, there were no structures in the liquefied areas except in the NEC case.

3. Incremental construction: Incremental housing is an important housing process practiced in Nepal whereby house owners incrementally add floors to their buildings as per their needs and financial situations. Adding floors to existing buildings in Nepal is a ubiquitous practice, but is seldom accompanied by seismic strengthening.

Vulnerability to seismic hazards tend to increase with additional floors and discontinuous expansions, which can be treated as additional vulnerability indicators in multivariate fragility models represented by earthquake fragility (probability of collapse vs. peak ground acceleration) curves shown in Figure 4 (Lallemant, Wong, Morales, & Kiremidjian, 2014). Lallemant, et al. (2014) predict that the expected number of buildings sustaining heavy damage or nearly collapsing in Kathmandu double every decade, which the authors say, is an underestimate given that vulnerability due to incremental construction has not been directly incorporated in the study.



Figure 4: Typical process of incremental building construction (top), and corresponding hypothetical fragility curves (bottom)

Source: Lallemant, et al., 2014.

Plate 5: Typical construction- and structural deficiencies observed in both URM and RCC buildings in the 2015 earthquakes

(a) Soft story and structural pounding failure

(Gautam, et al., 2016)

(b) Damage to adjacent buildings by collapsed

building (Himal Media, 2015)



(c-i) Eruption of sand due to liquefaction in NEC

area (Okamura et al., 2015)

(c-ii) Relative settlement of 3-6 cm in the NEC

buildings due to liquefaction (Earthquake

Engineering Group, et al., 2015)

(d) Tilted building in Balaju, Kathmandu due to

foundation failure (Wijeyewickrema et al., 2015)



4.2 Government Office Buildings

Out of 281 government office buildings assessed (Map 3, Table C1 in Annex C), 92.2% lie on moderate to high liquefaction zones including 41.3% on high liquefaction zone (Table 2). This suggests that liquefaction susceptibility has not been a major deciding factor for site selection of government buildings.

Table 5: Damage rating vs. liquefaction potential for government office buildings

Liquefaction Zone Damage Rating Total %

Red Yellow Green

High 12 (10.3%) 19 (16.4%) 85 (73.3%) 116 (100%) 41.3

Moderate 11 (7.7%) 27 (18.9%) 105 (73.4%) 143 (100%) 50.9

Low to none 1 (4.5%) 7 (31.8%) 14 (63.6%) 22 (100%) 7.8

Total 24 (8.5%) 53 (18.9%) 204 (72.6%) 281(100%) 100.0

Slightly less than 3/4th (72.6%) of 281 government office buildings assessed survived the 2015 Earthquakes without any significant damage (Figure 2). Although the share of buildings rated „red‟ or unfit for further use is relatively low at 8.5%, the absolute number of such buildings turns out to be 24, which cannot be ignored particularly because huge resources are consumed for the construction of government office buildings. In addition, loss of government buildings also implies interruption of public services until alternative management is in place which requires time and resources.

Figure 5: Damage rating vs. liquefaction potential for government office buildings

It is to be noted that out of 24 „red‟ buildings, half are located on high liquefaction zone. On the other hand, 73.3% of the buildings located on high liquefaction zone survived undamaged with a „green‟ tag. This suggests that although site selection deserves attention, with right construction technology, it is possible to mitigate site-specific adverse effects to some extent.

Figure 3 depicts catchment population of select government office buildings assessed. It shows, albeit in retrospection, the suitability of these building premises (with sizeable open spaces) to provide transitional shelter in case of 2015-like earthquakes. Public access to these open spaces in normal situation is mostly restricted. However, in case of emergency, these open spaces along with buildings can serve as place for temporary shelter as practiced in several countries such as Japan.

12 11 19 27

85 105

0

25

50

75

100

125

150

High Moderate Low tonone

No

. of

bu

ildin

g u

nit

s

Liquefaction Potential

Government Office Buildings (Damage Rating)

Green Yellow Red

12 19

85 11 27

105

1 7

14

0

50

100

150

200

250

Red Yellow Green

No

. of

bu

ildin

g u

nit

s

Damage Rating

Government Office Buildings (Liquefaction Potential)

Low to none Moderate High



Wall cracks in TU (Photo Credit: Prof Dr. Sudha Shrestha)

Wall cracks in IOE A Block (Photo Credit: Prof Dr. Sudha Shrestha)

Damage in Singha Durbar Complex (Photo Credit: Ekantipur

Beam Wall Separation (Photo Credit: Prof Dr. Sudha Shrestha)



Map 3: Damage rating of government office buildings assessed



Figure 6: Catchment population of select government office buildings assessed



4.3 Public Hospital Buildings

Hospital buildings are important infrastructures providing services to a large number of people at any given time, most of whom are patients and medical professionals. Hospitals are also the places which need to be functional throughout the day, week or year. Huge investment in terms of medical equipment also make hospital buildings economically more vulnerable to natural hazards. It is, therefore, a matter of relief that very few hospital suffered serious damage in the 2015 Earthquakes.

Out of 82 hospital buildings assessed (Map 4), only 5 buildings (6.1%) were rated as „red‟ (Table 3, Figure 4). Out of 22 buildings on high liquefaction zone, there were 2 „red‟ buildings. About 80% of the hospital buildings survived earthquakes with no damage.

Table 6: Damage rating vs. liquefaction potential for public hospital buildings


Red Yellow Green

High 2 (9.1%) 0 (0.0%) 20 (90.9%) 22 (100.0%) 26.8

Moderate 3 (5.5%) 9 (16.4%) 43 (78.2%) 55 (100.0%) 67.1

Low to none 0 (0.0%) 3 (60.0%) 2 (40.0%) 5 (100.0%) 6.1

Total 5 (6.1%) 12 (14.6%) 65 (79.3%) 82 (100.0%) 100.0

Figure 7: Damage rating vs. liquefaction potential for hospital buildings

Figure 5 depicts catchment population of hospital buildings assessed with sizeable open spaces within their premises (see also Table C5 in Annex C). It shows, albeit in retrospection, the suitability of these building premises (with sizeable open spaces) to provide transitional shelter in case of 2015-like earthquakes, or suitability of buildings themselves to cater to the post-earthquake emergency medical needs given their catchment population, which is large for some hospitals.

2 3 9

3

20

43

2 0

10

20

30

40

50

60

High ModerateLow/none

No

. of

bu

ildin

g u

nit

s


Hospital Buildings (Damage Rating)

Green Yellow

2

20 3 9

43

3

2

0

10

20

30

40

50

60

70

Red Yellow Green

No

. of

bu

ildin

g u

nit

s

Damage Rating

Hospital Buildings (Liquefaction Potential)

Low/none Moderate



Map 4: Damage rating of hospital buildings assessed



Figure 8: Catchment population of select hospital buildings assessed

4.4 Public Academic Buildings

Out of 283 public academic buildings assessed (Map 5), slightly more than half (51.9%) of the buildings are located in high liquefaction zones (Table 4, Figure 6). Only about 3% of the buildings are located in low to no-risk zones. This suggests that liquefaction susceptibility has not been a major deciding factor for site selection of academic buildings.

Slightly more than half (51.6%) of 283 public academic buildings assessed survived the 2015 Earthquakes without any significant damage. However, 73 buildings (25.8% of the total) were found to be unfit for further use. Out of 147 buildings located in high liquefaction zones, 45 buildings (30.6%) were rated „red‟ which is a significant proportion compared to about 19% „red‟ buildings located in the moderate liquefaction zone.

Table 7: Damage rating vs. liquefaction potential for public academic buildings


Red Yellow Green

High 45 (30.6%) 29 (19.7%) 73 (49.7%) 147 (100%) 51.9

Moderate 24 (18.9%) 33 (26.0%) 70 (55.1%) 127 (100%) 44.9

Very low/No 4 (44.4%) 2 (22.2%) 3 (33.3%) 9 (100%) 3.2

Total 73 (25.8%) 64 (22.6%) 146 (51.6%) 283 (100%) 100.0

0

15

30

45

60

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Hospital Buildings (Damage Rating vs. Catchment Population)

Red

Yellow

Green

Catchment Population - Estimated(2015)



Map 5: Damage rating of academic buildings assessed




Figure 7 depicts catchment population of select public academic buildings assessed (see also Table C5 in Annex C). It shows, albeit in retrospection, the suitability of these building premises (with sizeable open spaces) to provide transitional shelter in case of 2015-like earthquakes. Premises of IOE and Tribhuvan University (TU) in Kirtipur were, in fact, used by earthquake-affected locals for many days. TU had several „red‟ buildings but its large open space accommodated many temporary shelter seekers.

Figure 10: Catchment population of select academic buildings assessed

The availability of information on age of 52 public academic buildings assessed by the IOE teams allows analysis of the effect of ageing on buildings‟ performance against the 2015 Earthquakes (Table 5). As is evident, older buildings were mostly rated „red‟.

45 24

29

33

73

70

0

25

50

75

100

125

150

High Moderate VeryLow/No

No

. of

bu

ildin

g u

nit

s


Public Academic Buildings (Damage Rating)

Green Yellow Red

45 29

73

24 33

70

4 2

3

0

25

50

75

100

125

150

Red Yellow Green

No

. of

bu

ildin

g u

nit

s

Damage Rating

Public Academic Buildings (Liquefaction Potential)

Very Low/No Moderate High

01020304050607080

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No

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Public Academic Buildings (Damage Rating vs. Catchment Population)

Red Yellow Green Catchment Population - Estimated(2015)



Table 8: Damage rating vs. age of select public academic buildings

S. N. Age (Years)

Rating Liquefaction Zone Cumulative Count

Red Yellow Green

1 5 Yellow High

1 2 5 Yellow High

2

3 9 Yellow High

3 4 9 Yellow High

4

5 12 Green High

1 6 12 Green High

2

7 15 Yellow High

5 8 16 Yellow High

6

9 16 Green High

3 10 17 Yellow High

7

11 17 Green High

4 12 18 Yellow High

8

13 20 Yellow High

9 14 20 Red High 1

15 20 Green High

5 16 22 Green High

6

17 23 Red High 2 18 24 Green High

7

19 25 Green High

8 20 27 Yellow Moderate

10

21 27 Green Moderate

9 22 30 Green High

10

23 31 Green High

11 24 33 Green High

12

25 35 Yellow Moderate

11 26 35 Yellow Moderate

12


13 28 37 Red Moderate 3

29 40 Yellow High

14 30 40 Green High

13


14 32 45 Red High 4


15 34 48 Red High 5


15 36 50 Red High 6

37 50 Green High

16 38 50 Green High

17

39 50 Red Moderate 7 40 50 Green Moderate

18

41 51 Red High 8 42 51 Red High 9 43 51 Yellow Moderate

16

44 52 Red High 10 45 52 Red High 11 46 52 Red Moderate 12 47 52 Red Moderate 13 48 54 Red Moderate 14 49 55 Green Moderate

19

50 59 Red Moderate 15 51 70 Green Moderate

20

52 97 Red Moderate 16

The plot of cumulative count of buildings segregated on the basis of damage rating against the building age suggests a clear effect of ageing on damage (Figure 8). For instance, 11 out 16 „red‟ buildings are aged 50 years or more. In comparison, only 1 out of 16 „yellow‟ buildings and 5 out of 20 „green‟ buildings have reached or crossed the half-century mark. In contrast, only 2 out of 16 „red‟ buildings are aged less than 25 years. As evident from Figure 8, the plot of cumulative count of buildings versus age in the case of



„red‟ buildings produces S-shaped or logistic curves "exhibiting a progression from small beginnings that accelerates and approaches a climax over time".14

Figure 11: Cumulative count of select academic buildings versus damage rating

The age of building is one of the most neglected aspects of building vulnerability assessment. There is no regulation that restricts the use of buildings over certain age. The aforementioned results suggest that there should be a cap on the age of buildings.

4.5 High-Rise Apartment Buildings

Although apartment buildings are private properties, these are built to accommodate large number of households and are, therefore, of great public interest and concern. Because of the 2015 earthquakes, high-rise apartment buildings have been seriously affected not much from the structural safety point of view but from psychological concerns. Many high-rise apartments remain vacant as a result.

Out of 30 high-rise apartments assessed (Map 6, Table C4 in Annex C), 2 buildings (Park View Horizon Apartment in Dhapasi, and Kuleshwor Apartment, Oriental Phase II in Kuleshwor) were rated „red‟, and both buildings were located either in high or moderate liquefaction zone (Table 6, Figure 9). It is to be noted that Dhapasi where Park View Horizon Apartment – the most severely damaged high-rise building – is located is known as high liquefaction prone area.

Table 9: Damage rating vs. liquefaction potential for high-rise residential buildings


Red Yellow Green

High 1 (10.0%) 9 (90.0%) 0 (0.0%) 10 (100.0%) 33.3

Moderate 1 (7.1%) 9 (64.3%) 4 (28.6%) 14 (100.0%) 46.7

Low to none 0(0.0%) 6 (100.0%) 0 (0.0%) 6 (100.0%) 20.0

Total 2 (6.7%) 24 (80.0%) 4 (13.3%) 30 (100.0%) 100.0

More noticeable result, however, is that only 4 buildings managed to acquire „green‟ rating.

14

https://en.wikipedia.org/wiki/Sigmoid_curve.

0

5

10

15

20

25

0 25 50 75 100

Cu

mu

lati

ve C

ou

nt

Building Age (Years)

Cumulative Count of Buildings and Damage Rating

Red Yellow Green




Plate 6: Park View Apartment in Dhapasi, Kathmandu after the earthquake

Source: Wijeyewickrema, et al., 2015.

1 1

9 9

6

4

0

2

4

6

8

10

12

14

16

High Moderate Very lowto none

No

. of

bu

ildin

g u

nit

s


High-rise Apartment Buildings (Damage Rating)

Green Yellow Red

1

9 1

9

4

6

0

5

10

15

20

25

30

Red Yellow Green

No

. of

bu

ildin

g u

nit

s

Damage Rating

High-rise Apartment Buildings (Liquefaction Potential)

Very low to none Moderate High



Map 6: Damage rating of high-rise buildings assessed



V. POLICY IMPLICATIONS

The devastating earthquakes that occurred on April/May 2015 exposed the degree of vulnerability of buildings to seismic shocks. Nevertheless, the events have left valuable lessons for reconstruction, rehabilitation and new construction of buildings and settlements. More than a year after the last earthquakes, many damaged buildings in the Kathmandu Valley have already been re-built or replaced. However, the question is whether the government policy of “building back better” (NPC, 2015) is being addressed or not.

If lessons are not learnt from the devastation, vulnerability of buildings to earthquake risks will persist. It can never be forgot that Nepal was, is and will always remain earthquake-prone area. Through safe reconstruction, rehabilitation, and new construction, vulnerability can be reduced; some residual vulnerability will remain, which could be addressed gradually (Figure 13).

Figure 13: The way forward

Based on the analysis and synthesis of primary and secondary data on the RVDA of different types of buildings, this study puts forth policy measures to reduce seismic vulnerability (Table #).15 The key issues and concerns are categorized as follows: (1) architectural design, (2) structural design, (3) soil conditions (liquefaction and other weak soil conditions), (4) building materials, (5) workmanship, (6) incremental construction, (7) high-rise construction, (8) age of buildings, (9) public buildings as temporary shelters,16 (10) institutional capacity, and (11) pre-disaster vulnerability assessment. Recommended actions are accordingly described.

15

Note that the rapid assessments of building damages were not followed by detailed investigation because of which the RVDA results are the best source of information and reference vis-à-vis the effect of last earthquakes on buildings.

16 Based on discussion with Dr. Jibgar Joshi, regional planner and former planning bureaucrat.



Table 10: Key issues, concerns, and recommended actions

Key Issues and Concerns Actions Responsible Agency

Remarks

1. Architectural design

Key concerns:

- Soft-story

- Load path discontinuity

- Asymmetry in terms of plans or elevations

- Slenderness

- Heavy load accumulation

- Floating column

1.1 Update NBC to address issues brought forth by new building topologies adopted by architects/designers, lessons learnt from the earthquakes and to incorporate new scientific knowledge.

- DUDBC/MOUD - While architects/designers‟ creative interests should be respected, the implication of design on the structural robustness of buildings should also be considered along with the soundness of structural design and quality of workmanship that go into the actual construction of the buildings.

1.2 Develop by all municipalities locally appropriate building byelaws regulating the design of buildings appropriate for the corresponding neighborhoods given the extent of development, existing building typologies, desired density and ambience, and status of accessibility.

- DUDBC/MOUD

- Municipalities/ MOFALD

1.3 Implement NBC and building byelaws effectively and efficiently through:

- Regular consultations with homeowners, landowners, engineers, architects, and developers

- Gradual migration to online system for the compliance of NBC and building byelaws

- Carrot-and-stick policy (i.e., reward good practices and punish defaulters).


2. Structural design

Key concerns:

- Infill wall damages

- Pounding effects

- Poor connections of structural elements

- Compromise in reinforcement bars

- Lack of structural detailing

2.1 In addition to (1.1) above, address in the revised NBC the effect of brick infill walls on the lateral force resisting system of the RC frame, particularly in the case of important buildings such as the high-rise apartments (e.g., inclusion of measures such as diagonal bracing).

2.2 Prepare guidelines on retrofitting and provide trainings to engineers, builders and workers engaged in the rehabilitation of damaged buildings.

- DUDBC - At present, buildings satisfying both of the following criteria are exempted: (i) plinth area less than 1000 sq. feet, and (ii) number of stories not more than three.

- Structural analysis, design and supervision should be done by qualified structural engineering practitioner (not all engineering graduates have required skills and confidence).

2.3 Make structural analysis, design and supervision mandatory for all types of buildings.

2.4 Mobilize volunteer engineers to assist municipal engineers, particularly to provide services to low-income homebuilders, and gain practical knowledge





Remarks

3. Soil conditions (liquefaction and other weak soil conditions)

Key concerns:

- Foundation failure

- Soil failure (differential settlement)

3.1 Prepare and implement land use zoning depicting housing and non-housing areas depending on the soil conditions taking also reference of Land Use

Policy 2014 (and forthcoming related Act)17

.

3.2 Make soil tests mandatory for all types of buildings in high liquefaction areas).

- MOUD - Geological input in the design of foundations is still rare; structural engineers design the whole building including the foundation (Koirala, 2016).

- Liquefaction remains a constant threat in the Kathmandu Valley in case of future earthquakes (see Okamura, et al., 2015).

- Soil tests are now mandatory in many municipalities for any building taller than 3 stories or larger than 1000 sft in plinth area.

3.3 Prepare detailed soil characteristics map of the Kathmandu Valley for local area planning.

- DMG - The existing geological map of the Kathmandu Valley (scale 1:50,000) is prepared for planning for regional scale and therefore not suitable for local area planning.

4. Building materials

Key concerns:

- Poor quality

- Improper storage

4.1 Disseminate information on selection and storage of construction materials (particularly vital in case of owner-built buildings).

- DUDBC/MOUD - Use of old stocks of cement, corroded reinforcement bars, and/or round-shaped aggregates is commonly observed problems regarding building materials.

5. Workmanship Key concerns:

- Poor structural detailing

- Concrete mixing and placement

5.1 Provide regular trainings to masons and other construction workers leading up to rostering of trained masons and gradually licensed masons.

- DUDBC/MOUD - As in the case of licensed engineers, organizing hitherto informal construction workers into rostered masons (or later licensed masons) will have far fetching positive effects not only on the structural safety of buildings but also on the city economy as well as on the dignity of occupation itself.

6. Incremental construction Key concerns:

- Increased vulnerability with each incremental addition

6.1 Allow extension in the existing buildings only after a thorough structural investigation based on NBC.

6.2 Discourage significant alteration in the extension of extension of buildings from what was approved during building permit issuance.


- Incremental housing is an important housing process in Nepal which is linked with housing affordability.

7. High-rise construction

Key concerns:

7.1 Allocate separate zones for high-rise construction with adequate open spaces and discourage

- DUDBC/MOUD - Although high-rise apartments survived major damage in the 2015 earthquakes, the buildings

17

The policy has divided land into seven categories: agricultural, forest, residential, commercial, public, industrial, and others. The main focus of the policy is to ensure that land is used according to the prescribed category.




Remarks

- Safety of the structure, occupants as well as neighboring buildings

mushrooming of tall structures in established low rise residential areas.

were vacated for weeks out of fear. Owners of the neighboring buildings also went through mental and psychological stress fearing the tall buildings would fall on theirs.

8. Age of buildings

Key concerns:

- Loss of strength over time

- Lack of repair

- Incremental construction on ageing buildings

8.1 Limit age of buildings beyond which no incremental construction would be allowed.

8.2 Limit age of buildings beyond which their continued use would be mandatorily reviewed.

8.3 Generate awareness on the necessity and methods of periodic repairs and retrofitting; also ref. (2.2).

- DUDBC/MOUD - In Nepal, it is common to see even dilapidated houses getting vertical extension. Even many government offices and some prominent public academic institutes are housed in old Rana-era palaces (durbar) which were built completely for different purposes.

9. Public buildings as temporary shelters

Key concerns:

- Safety of buildings and occupants

- Use of open/closed spaces

9.1 Make public buildings and premises ready to be used as temporary shelters in case of large-scale disaster, including the use of rooms, open spaces, and water and sanitation facilities, along with the provision of medical services.

9.2 Ensure safety of public buildings through independent evaluation of construction (see corresponding remark).

- DUDBC/MOUD

- MOHA

- DUDBC‟s remit as a regulator of NBC is compromised because DUDBC also designs and manages construction of selected public buildings (Koirala, 2016).

10. Institutional capacity

Key concerns:

- Lack of sufficient technical capacity and human resources at DUDBC and municipalities

10.1 Provide sufficient technical capacity and human resources to DUDBC and municipalities for ensuring compliance of NBC and building byelaws.

10.2 Recruit volunteer engineers and interns.

10.3 Collaborate with professional organizations and academia for knowledge and technical partnerships.

- Government of Nepal

- The institutional responsibility to ensure safe housing rests on the shoulders of DUDBC and municipalities. More specifically, DUDBC provides technical support to municipalities including on NBC implementation.

11. Pre-disaster vulnerability assessment

Key concerns:

- Prevalent vulnerability

11.1 Conduct pre-disaster vulnerability assessment, and keep GIS-based records of unsafe buildings for retrofitting or gradual removal

- DUDBC/MOUD

- Municipalities

- Pre-disaster vulnerability assessment identifies risky structures for possible intervention to prevent damages in case of future earthquakes.

Acronyms: DMG: Department of Mines and Geology; DUDBC: Department of Urban Development and Building Construction; MOFALD: Ministry of Federal Affairs and Local

Development; MOHA: Ministry of Home Affairs; NBC: National Building Code.



VI. CONCLUSION

Crisis also provides opportunity. The devastation caused by the last earthquakes has generated unprecedented public awareness on the importance of safe building construction and risk-resilient urban development.

This study has made the best use of available data on post-earthquake building assessment. The study utilizes data collected by government agencies on public buildings including offices and hospitals and on high-rise buildings as well as data on public academic buildings collected by the IOE teams. his study has revealed useful information in making meaningful contribution on a systematic research of building damage assessment. Based on the analysis and synthesis of primary and secondary data on the RVDA of different types of buildings, this study puts forth policy measures to reduce seismic vulnerability. The findings will be useful for policymakers, development groups and agencies, and researchers.



REFERENCES

Asian Development Bank (2013). Moving from risk to resilience: sustainable urban development in the Pacific. Mandaluyong City, Philippines: Asian Development Bank.

Earthquake Engineering Group; Ehime University Team; Mori, Shinichiro. (2015). Nepal Gorkha Earthquake, 2015 Preliminary Damage Survey Reporting Seminar of JSCE at University of Tokyo.

Gautam, D., Rodrigues, H., Bhetwal, K. K., Neupane, P., & Sanada, Y. (2016). Common structural and construction deficiencies of Nepalese buildings. Innovative Infrastructure Solutions, 1:1.

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Post-Earthquake Rapid Visual Damage Assessment of · PDF file · 2017-03-28initiated research study to contribute towards informed ... 3Analysis of public buildings and high-rise