Rapid Visual Screening for Seismic Evaluation of...

Rapid Visual Screening for Seismic Evaluation of Existing Buildings

in Himachal Pradesh

by

Pradeep Kumar Ramancharla, Rajaram Chenna, Swajit Singh Goud, Ajay Kumar Sreerama, Gugan Vignesh,Bhargavi Sattar, Narender Bodige, Ravikanth Ch, Pulkit Velani, Raju Sangem, Krishna Babu

Report No: IIIT/TR/2014/-1

Centre for Earthquake EngineeringInternational Institute of Information Technology

Hyderabad - 500 032, INDIAApril 2014

Project Completion Report

Rapid Visual Screening for Seismic Evaluation of Existing Buildings in

Himachal Pradesh

Project Sponsored By

TARU Leading Edge Private Limited, New Delhi

Submitted By

International Institute of Information Technology (IIIT), Hyderabad

Technical Report No. 01-2014

Volume-I

April - 2014

Rapid Visual Screening of Himachal Pradesh

2

Participants

From

International Institute of Information Technology, Hyderabad

Ramancharla Pradeep Kumar

Chenna Rajaram

Swajit Singh Goud

Ajay Kumar Sreerama

Gugan Vignesh Selvaraj

Sattar Bhargavi

Bodige Narender

Ravikanth Chittiprolu

Pulkit Velani Dilip

Raju Sangam

Krishna Babu

From

TARU Leading Edge Private Limited, New Delhi

Shashank Mishra


3

Table of Contents

1. Introduction………………………………………...……………………………….….……6

2. Vulnerability Studies of cities…………….…………………………………….…….……6

2.1 Tehra, Iran…………….…………………………………………………...….…….……6

2.2 Dehradun, India…………….…………..………………………………...….…….……7

2.3 Basel, Switzerland………….…………..………………………………...….….….……7

2.4 Kanpur, India………….………….……..………………………………...….…….……7

2.5 Zeytinburnu, Turkey………….………….……..………...……………...….…….……7

2.6 Gandhidham, India………….…………….……………………………...….…….……7

3. Literature on vulnerability assessment methods………………………………….…..…8

3.1 International Practices in RVS………….………………….……..……...….…….……8

3.2 RVS methods in USA………...………….………………….……..……...….…….……8

3.3 FEMA 154……………………..………….………………….……..……...….…….……8

3.4 RVS in Greece………………...………….………………….……..……...….……...…10

3.5 RVS in Canada...……………...………….………………….……..……...….……...…10

3.6 RVS in Japan..………………...………….………………….……..……...….…….…..10

3.7 RVS in New Zealand………...………….………………….……..……...….……...…11

3.8 RVS in India………...………...………….………………….……..……...….…….…..11

4. Methodology………….…………………………………………………………………….11

4.1 Rapid Visual Screening………….…………………………………………………….11

4.1.1 Brick Masonry buildings...…………………………………………………….17

4.1.2 Hybrid buildings...…………….……………………………………………….17

4.1.3 Rammed earth buildings...…………….…………..………………………….17

4.1.4 Reinforced concrete buildings...…………….…………….... ………………..17

4.1.5 Stone masonry buildings...…………..……….……………... ……………….18

4.2 Preliminary Survey………….…………...…………………………………………….18

5. Conclusions…...…………………………………………………………………………….21

6. References…………………………………………………………………...……………...21


4

List of figures

1. Location of brick masonry buildings through RVS in the districts of Himachal Pradesh…………………………..…………………………………………………..….12

2. Normal distribution curve for brick masonry buildings through RVS ……….....12

3. Location of Hybrid buildings through RVS in the districts of Himachal Pradesh …………………………………………………………………………………13

4. Normal distribution curve for Hybrid buildings through RVS…………………...14

5. Location of Rammed earth buildings through RVS in the districts of Himachal Pradesh ……………………………….……………………………..………………….14

6. Normal distribution curve for Rammed earth buildings through RVS …………15

7. Location of Reinforced concrete buildings through RVS in the districts of Himachal Pradesh ……………………………………………………………..………15

8. Normal distribution curve for Reinforced Concrete buildings through RVS....…16

9. Location of stone masonry buildings through RVS in the districts of Himachal Pradesh…………………………………………………………………………..……...16

10. Normal distribution curve for Stone masonry buildings through RVS ………….17

11. Normal distribution curve typology wise ………………………………......………18

12. Schematic diagram of assessment of building …………………………..………….21


5

List of tables

1. Statistics of surveyed buildings in 6 districts of Himachal Pradesh ….…..……...19

2. Details of surveyed buildings typology wise ………………………………………19


6

Abstract

India faces serious earthquake problems by a rapid growth of urban population. Nearly 60% of landmass in India is under moderate to severe earthquake prone area. During 2001 Bhuj earthquake, massive damage was happened to moderate buildings. Reconnaissance survey reports suggested that the need for seismic evaluation of existing buildings. Different methods for seismic evaluation of existing buildings have developed in various countries. Most of the methods follow three level assessment procedures (or something quite similar to it) namely, (a) rapid visual screening, (b) preliminary assessment, and (c) detailed evaluation.

Rapid Visual Screening (RVS) was conducted on 9099 buildings in Himachal Pradesh state. In this study, five different typologies like Reinforced Concrete, Brick Masonry, Stone Masonry, Hybrid and Rammed Earth buildings were selected. The RVS methodology is referred to as a “sidewalk survey” in which an experienced screener visually examines a building to identify features that affect the seismic performance of the building, such as the building type, seismic zone, soil conditions, horizontal and vertical irregularities, apparent quality in masonry and RC structures and short column etc. This walk survey is carried out based on the checklists provided in a proforma for all five typology of buildings. Other important data regarding the building is also gathered during the screening, including the occupancy of the building and the presence of nonstructural falling hazards. A performance score is calculated for the building based on numerical values on the RVS form corresponding to these features. The performance score is compared to a “cut-off” score to determine whether a building has potential vulnerabilities that should be evaluated further by an experienced engineer. Gaussian distribution is applied for cut off score in this study. An attempt has been made to do rapid visual screening of five varieties of buildings in Himachal Pradesh state. RVS score has calculated for 9099 buildings and plotted normal distribution curves for each typology of building to understand the distribution of buildings in HP state. From the study, it is clearly shown that Kangra district have more buildings in all five different typologies. As per statistics of surveyed buildings by TARU consultants in Himachal Pradesh,

around 17% (1541 out of 9099) of buildings are reinforced concrete, 48% (4363 out of

9099) of buildings are brick masonry, 15% (1341 out of 9099) of buildings are stone

masonry, 5% (518 out of 9099) of buildings are rammed earth and 15% (1318 out of

9099) of buildings are hybrid. However, there are some low RVS score buildings which

are potentially vulnerable to future earthquakes. Also it is suggested that preliminary

analysis needs to be performed on 47 buildings and detailed analysis for 15 buildings

for calibrating RVS scores.


7

1. Introduction

India faces serious earthquake problems by a rapid growth of urban population. Nearly 60% of landmass in India is under moderate to severe earthquake prone area. Bihar-Nepal border (M6.4) in 1988, Uttarkashi, Uttaranchal (M6.6) in 1991, Latur, Maharastra (M6.3) in 1993, Jabalpur, Madhya Pradesh (M6.0) in 1997, Chamoli, Uttaranchal (M6.8) in 1999, Bhuj, Gujarat (Mw7.7) in 2001 and Muzzafarabad, Kashmir (M7.2) in 2005 and Sikkim (M6.8) in 2011. These earthquakes caused around 2 lakh causalities. However, similar high intensity earthquakes in the US, Japan, etc., do not lead to such an enormous loss of lives, as the structures in these countries are earthquake resistant. During 2001 Bhuj earthquake, massive damage was happened to moderate buildings. Reconnaissance survey reports (Jain S. K, 2005) suggested that the need for seismic evaluation of existing buildings. In India as well as worldwide RVS has been done for a maximum of few hundred buildings. It is for the first time that the number like 16000 has done in the state of Gujarat (Srikanth et al, 2010). In this study, an attempt has been made to do RVS for five different typologies like Reinforced Concrete, Brick Masonry, Stone Masonry, Hybrid and Rammed Earth buildings. As per the Indian Standards seismic zonation map, Himachal Pradesh state falls in Zone IV and V. And five districts, namely Chamba, Hamirpur, Kangra, Kullu, Mandi have liable to the severest design intensity of MSK IX or more, the remaining area of these districts are liable to the next severe intensity VIII. Two districts, Bilaspur and Una have also substantial area in MSK IX and rest in MSK VIII. The remaining districts also are liable to intensity VIII. Besides, the earthquake, the people of HP have also affected by several natural hazards like landslides, avalanches, floods, fires etc. Figure 1 shows district names to be surveyed in Himachal Pradesh. Different methods for seismic evaluation of existing buildings have developed in various countries. Most of the methods follow three level assessment procedures (or something quite similar to it namely, (a) Phase-I: Rapid visual screening, (b) Phase-II: Preliminary assessment, and (c) Phase-III: Detailed evaluation.

2. Vulnerability Studies of Cities Vulnerability assessment of cities has been performed in the past based on population loss estimation and estimation of direct and indirect losses due to various disasters (Keya Mitra, 2008). The various methods for the vulnerability assessment of buildings differ in time spent for each building and the degree of analysis that a building is subjected to. Some recent vulnerability assessment studies are discussed in the following sections:


8

Figure 1. Districts considered for RVS in Himachal Pradesh

2.1 Tehra, Iran Seismic vulnerability assessment in the city of Tehran (Keya Mitra, 2008) was done based on database collection and damage estimation for buildings for two earthquake scenarios. A visual survey was carried out to identify the condition of buildings and type of occupancy. Seismic building damage for earthquake scenarios were derived from HAZUS software ranging from slight to complete degree of damage. Most of the buildings in the study area were found to be vulnerable considering the two earthquake scenarios. The recommendation of the study was that to secure lives and property in the study area.

2.2 Dehradun, India The vulnerability assessment in Uttaranchal was done by singh in 2005. This study developed a methodology for loss estimation based on building and population loss. A GIS based tool was developed for primarily population loss estimation. The research was broadly concluded that in a predominantly residential area, population distribution and census sources.

2.3 Basel, Switzerland The evaluation of seismic vulnerability of existing residential building in the city of Basel, Switzerland (Keya Mitra, 2008) was undertaken to improve the assessment of seismic hazard, to investigate the vulnerability of the built environment. Since no major damaging earthquake has occurred in Switzerland in recent years, vulnerability functions from observed damage patterns were not


9

available. A simple evaluation method based on engineering models of the building structures suitable for the evaluation of a larger number of buildings was therefore proposed. The study concluded that it was not feasible to evaluate each individual building in a large area, even though large number of buildings could be evaluated in the study. Hence a classification of buildings was proposed to allow the extrapolation of the results for the use of earthquake scenario.

2.4 Kanpur, India Preliminary evaluation based on IITK-GSDMA guidelines were carried out on 30 representative multistoried RC buildings. The study revealed that large openings, horizontal and vertical projections, presence of soft and weak storeys and short column effects are major weaknesses in the buildings at Kanpur from seismic safety point of view. This study concluded that strict enforcement mechanisms for implementation of IS codes.

2.5 Zeytinburnu, Turkey This study is an implementation of the earthquake master plan for Istanbul metropolitan area in the Zeytinburnu district with a population of 240,000 and more than 16,000 buildings (Keya Mitra, 2008). As a part of seismic vulnerability of existing building, a multi stage seismic safety assessment was performed.

2.6 Gandhidham, India Rapid Visual Screening (RVS) was conducted around 20,000 buildings in Gandhidham and Adipur cities (Srikanth et.al, 2010). Though, construction practices are varied, about 26% of buildings were predominantly RCC type and 74% of masonry structure were found. RVS score of these structures reveal that in general buildings are of low quality and further evaluation and strengthening of buildings is recommended. The procedure adopted in this study is three tier method, i.e., rapid visual screening, preliminary assessment and detailed assessment.

3. Literature on Vulnerability Assessment Methods Most of the methods for seismic evaluation of building follow three levels of assessment. RVS methods vary from those requiring 15-30 minutes on site for each building to more detailed ones involving some basic calculations. Preliminary assessment techniques are employed to analyze the building performance when a more reliable assessment is required. This requires detailed information regarding the structural components, material properties and site conditions. The in-depth evaluation through sophisticated structural analysis falls within the third category of vulnerability assessment. The worldwide practices are as follows:


10

3.1 International Practices in RVS RVS can be very valuable to prioritize the buildings to be further studied so that technical and other resources could be most effectively utilized. The procedure involves side walk survey either without entering the building or doing so for a short duration only (15-45 minutes). RVS is useful when the number of buildings to be evaluated is large, since even non-engineers may collect data and assign scores. However, uncertainty and non availability of the details can result in widely differing interpretations of the criteria by different individuals leading to inconsistent results.

3.2 RVS Methodologies in the USA A number of guidelines were developed by the federal emergency management agency (FEMA) in the USA for seismic risk assessment and rehabilitation of buildings. These includes FEMA 178(1992) published in 1989 and revised in 1992, FEMA 310(1998) developed as revised version of FEMA 178, FEMA 154(2002) for rapid visual screening of buildings. The RVS method was originally developed by the applied technology council (ATC) in the late 1980s and published in 1988 in the FEMA 154 Report. FEMA 310 includes a process for seismic evaluation of existing buildings, with the introduction of an analysis procedure for screening, preliminary evaluation and detailed evaluation.

3.3 FEMA 154 The basis of FEMA 154 is the ATC 13 report (ATC: 13-1988) on earthquake damage evaluation data for facilities in California which includes background information, detailed description of methodology used to develop the required earthquake damage/loss estimates, inventory information and damage probability matrices for different facility types and estimates as well as the time required to restore damaged facilities to their pre-earthquake usability. These were developed by a project engineering panel composed of senior level specialists in earthquake engineering. a. FEMA: 154 -1988 (First edition) In developing a handbook on rapid visual screening of seismically hazardous buildings, ATC evaluated procedures, recommended a rapid screening procedure and developed supplementary information on heavy debris removal and urban rescue. The basic structural hazard scores in the first edition of FEMA 154 were calculated using (1) expert-opinion damage probability matrices from the ATC-13 report, earthquake damage evaluation data for California (ATC,1985) modified for use in regions outside of California and (2) ground motion maps provided with the NEHRP recommended provisions for the development of seismic regulations for new buildings (BSSC,1985), which specified effective peak acceleration ground motion having a 10% probability of being exceeded in 50 years. FEMA: 155-2002, performance modification factors (PMF) developed in the first edition were related to significant deviations from the normal structural practice or conditions, or had to do with the effects of soil amplification on the expected ground motion.


11

Deviations from the normal structural practice are varied and numbers are quite large for different building types. Many of these cannot be detected from the street on the basis of a rapid visual inspection. On account of this, and based on querying of experts and checklists from ATC 14, a limited number of most significant factors were identified. These factors were limited to those having an especially severe impact on seismic performance. Those that could not be readily observed from the street were eliminated. The PMFs were assigned values, based on judgment, such that when applied to the basic structural hazard scores, the resulting modified score would approximate the probability of major damage given the presence of that factor. As discussed in FEMA: 155-2002, the PMFs in the first edition were based on engineering judgment, lacked analytically basis. b. FEMA: 154 -2002 (Second edition) Several significant changes and enhancements were incorporated in the second edition of the FEMA 154 handbook as follows: An updated scoring system, formatted as in the scoring system in the first edition and consisting of

a. New Basic structural hazard scores based on (1) the HAZUS methodology and fragility curves (NIBS,1999) for low rise buildings and assuming soil type B and (2) new maximum considered earthquake seismic design spectral acceleration response values (developed by the USGS and building seismic safety council), which are based on ground motion having a 2% probability of being exceeded in 50 years, adjusted to incorporated the 2/3 reduction factor specified in the FEMA 319 handbook for the seismic evaluation of buildings-A pre standard (ASCE,1998); and

b. Performance modification factors were renamed as score modifiers

c. New scores modifiers were proposed for mid rise building, high rise buildings, plan irregularity, vertical irregularity, pre-code buildings, post-benchmark buildings, soil type C, soil type D, soil type E. One of these modifiers was based on calculations to reflect the HAZUS fragility curves and methodology. The vertical irregularity was left to judgment. A comparison between the performances score modifiers of FEMA and the earthquake engineering building characteristics listed in ATC 13 (1985) reveals the rationale for the judgment of practicing engineers that led to the performance modification factors in FEMA 154 first edition and retained in the second edition (2002) with changes in the numerical values of the same. These have been summarized in table 5.1. An important change was in the score modifier in FEMA 1st Edition were less than zero implying penalties. This was indicative of judgment of that time that the vulnerability of high rise buildings to earthquakes was higher that low rise buildings. Hence, score modifiers for


12

the mid rise and high rise buildings is generally positive in the second edition indicating advantages given for the better design and construction that these buildings are likely to posses.

3.4 RVS in Greece A fuzzy logic based rapid visual screening procedure was developed in Greece (Demartinos and Dritsos, 2006) for the categorization of buildings into five different damage grades in the event of future earthquake. The method was developed on 102 buildings affected by 1999 Athens earthquake. The above based RVS proposed a probabilistic reasoning method that treats the structural properties of a building in a holistic way and gives a score that represents possible damage in the case of major seismic event, defined as earthquakes that produce ground accelerations equivalent to the values provided by the relevant codes. The evaluation of output variables through the fuzzy inference process involves the evaluation of all fuzzy rules that make up the system. For the sake of simplification, the developers of this method have proposed grouping of input variable to a set of four intermediate variables which are evaluated through fuzzy inference processing of the input variables. The damage score is evaluated through a fuzzy inference system. Higher damage scores indicate greater vulnerability.

3.5 RVS in Canada

The method is based on a seismic priority index which accounts for both structural and non-structural factors including soil conditions, building occupancy, building importance and falling hazards to life safety and a factor based on occupied density and the duration of occupancy.

3.6 RVS in Japan The procedure is based on seismic index for total earthquake resisting capacity of a storey which is estimated as the product of basic seismic index based on strength and ductility indices, an irregularity index and time index. The evaluation is based on very few parameters and lacks clarity regarding ranking of buildings based on a scoring or rating system.

3.7 RVS in New Zealand The New Zealand code recommends a two stage seismic performance evaluation of buildings. The initial evaluation procedure involves making an initial assessment of performance of existing buildings against the standard required for a new building. A percentage new building standard of 33 or less means that the building is assessed as “potentially earthquake prone” in terms of the building act and a more detailed evaluation of it will typically be required. The process requires the expertise of earthquake engineers to yield quality results.

3.8 RVS in India


13

There have been some efforts in India towards developing RVS methods. Sinha and Goyal have proposed a methodology for RVS of 10 different types of buildings. The procedure requires identification of the primary structural load carrying system and building attributes that are expected to modify the expected seismic performance for the lateral load resisting system under consideration. Building types have grouped into six vulnerable classes based on European Macro seismic scale (EMS) recommendations. Likely damage to structures have been categorized in different grades depending on their impact on the seismic strength of buildings and the damage levels used have been sourced from EMS.

4. Methodology A schematic diagram of assessing of any building is shown in figure 2. The evaluation is based on a few parameters of buildings. The parameters of the buildings are building height, frame action, pounding effect, structural irregularity, short columns, heavy overhang, soil conditions, falling hazard, apparent building quality, diaphragm action etc. On the basis of above mentioned parameters, performance score of the buildings has been calculated. The formula of the performance score is given as

PS= (BS) + ∑[(VSM) x (VS)] Where VSM represents the Vulnerability Score Modifiers and VS represents the Vulnerability Score that is multiplied with VSM to obtain the actual modifier to be applied to the BS or Basic Score. The data analysis of the existing buildings in the region is scrutinized on the basis of Gaussian (Normal) distribution. This distribution is commonly used for statistical analysis of large data. A normal distribution in a variate X with mean µ and variance σ is a statistical distribution with probability density function: Generally a cumulative probability refers to the probability that the value of a random variable falls within a specified range. Frequently, cumulative probabilities refer to the probability that a random variable is less than or equal to a specified value. The cumulative Distribution function, which gives the probability that a variate will assume a value ≤x, is then

2

2

x

e2

1)x(f

dxe2

1dx)x(P)x(D

x2

x2)x(

http://mathworld.wolfram.com/Variate.html

http://mathworld.wolfram.com/Mean.html

http://mathworld.wolfram.com/Variance.html

http://mathworld.wolfram.com/ProbabilityDensityFunction.html


14

From these two it is very convenient to represent the probability that the performance score is less than or equal to some specified values under the curve. Based on the scores of RVS, some percentage of structures will be selected for preliminary evaluation and further for detailed evaluation. RVS is useful when the number of buildings to be evaluated is large. In this survey, even non-engineers may collect data and assign scores. Finally correlation between three phases will be standardized for further application of seismic evaluation in other cities falling in zone IV and V of seismic zoning map of India. Based upon this complete evaluation we can develop strategies for both short-term and long-term mitigation and plans to reduce risk in different areas.

Figure 2. Schematic diagram of assessment of building


15

4.1 Phase-I: Rapid visual screening

In this project, an attempt has been made to survey 9099 building in Himachal Pradesh. The above buildings include five varieties of buildings namely, brick masonry, reinforced concrete, hybrid, stone masonry and rammed earth buildings. As a part of this project, RVS forms are generated for stone, hybrid and rammed earth buildings. RVS scores have calculated for the above buildings. A proforma of RVS sheet for all five buildings are shown in figure 3 to 7.


16

Figure 3 (a). Proforma for Brick Masonry Buildings (First page)

Figure 3 (b). Proforma for Brick Masonry Buildings (Second page)


17

Figure 4 (a). Proforma for Hybrid Buildings (First page)


18

Figure 4 (b). Proforma for Hybrid Buildings (Second page)


19

Figure 5 (a). Proforma for Reinforced Concrete Buildings (First page)


20

Figure 5 (b). Proforma for Reinforced Concrete Buildings (Second page)


21

Figure 6 (a). Proforma for Rammed Earth Buildings (First page)


22

Figure 6 (b). Proforma for Rammed Earth Buildings (Second page)


23

Figure 7 (a). Proforma for Stone Masonry Buildings (First page)


24

Figure 7 (b). Proforma for Stone Masonry Buildings (Second page)

This performance score mainly depends on soil type, building condition, architectural and earthquake resistance features. Other important data regarding the building is also gathered during the screening, including the occupancy of the building and the


25

presence of nonstructural falling hazards. In this, nonstructural interior components are not evaluated. The performance score is compared to a “cut-off” score to determine whether a building has potential vulnerabilities that should be evaluated further by an experienced engineer. From these scores, we can come to a conclusion on whether the building strength is adequate for earthquake forces likely to occur at the site. Many different types of damage can occur in buildings. Damage can be divided into two categories: structural and nonstructural, both of which can be hazardous to building occupants. Structural damage means degradation of building’s structural support systems (i.e. vertical and lateral force resisting systems), such as the building frames and walls. Nonstructural damage refers to any damage that does not affect the integrity of the structural support systems. Examples of nonstructural damage are chimneys collapsing, windows breaking, or ceilings falling. The type of damage to be exposed is a complex issue that depends on the structural type and age of the building, its configuration, construction materials, the site conditions, the proximity of the building to neighboring buildings, and the type of non structural elements. Structural parameters that have to be observed during the field surveys and the value given to each parameter by the observer are briefly given below.

4.1.1 Brick Masonry Buildings The basic components of masonry buildings are roofs, floor slabs, walls and foundations (spread wall footings). The walls and footings are mainly made of bricks or stones, laid in horizontal courses, with mortar filling up the gaps and providing the required bond between the units. Figure 8 shows typical view of brick masonry building.

Figure 8. Typical view of brick masonry building


26

4.1.2 Reinforced Concrete Structures In a framed building, the basic skeleton (frames) comprises of beams, columns and footings (fig. 9). The framework resists both vertical and lateral loads. Reinforced concrete is comprised of two basic materials, steel and concrete. The two materials work in a synergistic fashion when constructed properly to provide composite components which have very strong structural characteristics. Reinforced concrete is commonly used in structures designed for heavy use and long life, such as governmental and institutional buildings and public works structures. Concrete has a great capacity to support compressive loads. Steel has a great capacity to carry both compressive and tensile loads. Beams are horizontal structural components that support floors, ceilings, roofs, or decks (i.e., bridge and parking decks). The loads carried by a beam are primarily perpendicular to the longitudinal axis of the beam. A typical reinforced concrete beam is designed to allow the compressive forces to be carried by the concrete material and the tensile forces to be carried by the steel. Columns are vertical structural components that support beams and other structural elements. The compressive loads carried by columns are primarily parallel to the vertical or longitudinal axis of the column.

Figure 9. Typical view of RC building

4.1.3 Year of Construction In India, reinforced concrete structures are designed and detailed as per the Indian Code IS:456-2000. It was revised in year 2000 and IS:1893 code is revised in year 2002. Most of the buildings satisfy gravity and serviceability loads only. However, structures located in high seismic regions require ductile design and detailing. Provisions for the ductile detailing of monolithic reinforced concrete frame and shear wall structures are specified in IS:13920-1993. After the 2001 Bhuj earthquake, this code has been made mandatory for all structures in zones III, IV and V. Newer buildings generally sustain less damage than older buildings designed to earlier codes.


27

4.1.4 Number of Floors

This is the total number of floors above the ground level. The buildings were generally residential, although some were commercial and some mixed use involving residential accommodation above ground floor commercial premises.

4.1.5 Structural Irregularities Properly distributed lateral load resisting elements within the building lead to a regular structural configuration and better seismic performance. The structural walls should be uniformly distributed in both orthogonal directions of the building. They should be sufficient in number and strong enough to resist the expected seismic loads. In masonry buildings, horizontal vibrations can be most damaging, especially in situations where adequate walls are not present in both the orthogonal directions, or when the walls are not properly joined to adjacent walls. In low income residential areas, having small and narrow plots the houses may have two parallel walls in one direction only, with fewer walls in the perpendicular direction. In deep plots located in commercial areas, with comparatively narrow frontages, it is quite common in India to find buildings with walls only at the two ends along the long directions and no walls in the other direction, to accommodate clear floor space for display or storage. Such buildings are clearly very vulnerable. Figure 10 shows presence of structural irregularities in the building.

Figure 10. Structural irregularities are present in the building at Kangra district

4.1.6 Heavy Overhangs

Heavy overhangs are formed when projections of the actual habitable spaces, from the first floor upwards, are made to increase the available floor area in the upper floor


28

tenements. Buildings having such large and heavy cantilever projections have been observed to sustain heavy damage in earthquake events. Heavy balconies and overhanging floors in multistory reinforced concrete buildings shift the mass center upwards; accordingly give rise to increased seismic lateral forces and overturning moments during earthquakes. Heavy balconies and overhanging floors in reinforced concrete buildings shift the mass center upwards; accordingly increase seismic lateral forces and overturning moments during earthquakes. Buildings having balconies with large overhanging cantilever spans enclosed with heavy concrete parapets sustained heavier damages during the earthquakes compared to regular buildings in elevation. Since this building feature can easily be observed during a walk-down survey, it is included in the parameter set. Large cantilevers (projections supported only on one side) especially at upper floors are undesirable. Figure 11 shows presence of heavy overhangs on the top of building.

Figure 11. Heavy overhangs are present on the top of structure at Kangra district

4.1.7 Re-entrant Corners

The re-entrant, lack of continuity or “inside” corner (fig. 10) is the common characteristic of overall building configuration that, in plan, assume the shape of an L, T, H, +, or combination of these shapes. The dimension of the offset and the proportion of the derived wings will determine the vulnerability of a building. Each wing will react to the displacements and the torsional effects produced by ground motions in a different way. Under the action of earthquake forces, each wing will have a different dynamic behavior because of its particular stiffness and position relative to the direction of horizontal forces. The movement of different parts of the building can be very complicated, producing considerable diaphragm deformation, torsional effects and concentration of stress at the vertices of reentrant corners.


29

Figure 10. Re-entrant corners in buildings

4.1.8 Local Soil Conditions The intensity of ground motion at a particular site predominantly depends on the distance the causative fault and local soil conditions. There exists a strong correlation between Peak Ground Velocity (PGV) and the shear wave velocities of local soils. Site amplification is one of the major factors that increase the intensity of ground motions. Although it is difficult to obtain precise data during a street survey, an expert observer could be able to classify the local soils as stiff or soft. The geotechnical data provided by local authorities is a reliable source for classifying the local soil conditions. The risk of building increases, as the softness of soil increases. If the soil is sandy and is saturated with ground water, there is a possibility of liquefaction during earthquakes as the soil loses its firmness and behaves as a jelly.

4.1.9 Pounding Pounding is damage caused by two buildings, or different parts of a building, hitting one another. The number of buildings damaged by pounding is small. Pounding is the result of irregular response of adjacent buildings of different heights and of different dynamic characteristics. In situations where two buildings are located too close to each other, they may collide during strong shaking leading to substantial damage. The pounding effect is more pronounced in taller buildings (fig. 12). When building heights do not match, the roof of the shorter building may pound at the mid-height of the columns in the taller building; this can be quite dangerous, and can lead to story collapse.


30

Figure 12. Possible location of occurrence of pounding

4.1.10 Diaphragm Action

The diaphragm configuration is the shape and arrangement of horizontal resistance elements that transfer forces between vertical resistance elements. Diaphragms perform a crucial role in distributing forces to the vertical seismic resisting elements. The diaphragm acts as a horizontal beam, and its edges act as flanges. Geometrical irregularities are analogous to such irregularities in other building elements, leading to torsion and stress concentration. The horizontal inertia forces generated by the ground motion at different locations of the floor must be transferred to the vertical elements such as walls. For this, the floor must act as a diaphragm. Cast-in-situ reinforced concrete or reinforced brick slabs are quite effective as diaphragms. However, other types of floors such as timber, if not properly connected together, for seismic loading, may not provide the diaphragm action. Discontinuities in the diaphragm due to the presence of large cut outs hinder the ability of the diaphragm to transfer lateral forces to the walls. Diaphragms cannot be determined from building exteriors during rapid visual screening surveys and may be observed only if access to a building is possible. The same is true of cut outs in diaphragms. Considering the importance of proper diaphragm action in the seismic performance of buildings, a penalty modifier of -10 is proposed in situations where absence of proper diaphragm action can be confirmed. No modifiers are proposed for situations where diaphragm action is either present or undeterminable through visual screening alone.

4.1.11 Soft/weak stories A soft or weak storey is created when the lateral stiffness and/or strength of a storey is markedly more flexible than the floors above and below. This often occurs at the


31

ground floor when it is left open for parking, a shop front, or other reasons. Most of the deformation demand from the seismic event is concentrated at this level and results in large rotation demand in columns that have not been designed for ductility. Soft/weak storey collapses have been seen in many past earthquakes. Soft story usually exists in a building when the ground story has less stiffness and strength compared to the upper stories. This situation mostly arises in buildings located along the side of a main street. The ground stories, which have level access from the street, are employed as a street side store or a commercial space whereas residences occupy the upper stories. These upper stories benefit from the additional stiffness and strength provided by many partition walls, but the commercial space at the bottom is mostly left open between the frame members, for customer circulation. Besides, the ground stories may have taller clearances and a different axis system causing irregularity. The compound effect of all these negative features from the earthquake engineering perspective is identified as a soft story. Many buildings with soft stories were observed to collapse due to soft story in the past earthquakes all over the world.

4.1.12 Short Column Failure A short column failure is caused by its relatively high stiffness in comparison to other columns at that floor level. The transverse forces generated at a floor level are distributed in proportion to the member stiffness, therefore a short column will attract a greater proportion of the load and, when compared to a more slender member, will have less ability to withstand the deflections that will occur over their height. Frames with partial infill lead to the formation of short columns which sustain heavy damage since they are not designed for the high shear forces due to shortened heights that will result from a strong earthquake. Semi-in-filled frames, band windows at the semi-buried basements or mid-story beams around stairway shafts lead to the formation of short columns in concrete buildings. These captive columns usually sustain heavy damage during strong earthquakes since they are not originally designed to receive the high shear forces relevant to their shortened lengths. Short columns can be identified from outside because they usually form along the exterior axes.

4.1.13 Frame Action Load transfer means to support the loads acting on the building and to safely carry them down to the soil below. In a framed building, the loads are transferred by 'Frame Action'. First the loads are transferred from slabs to beams. Beams then transfer them to columns immediately below them. These columns transfer the loads to lower columns. While a beam carries the load for that floor only, a column carries the load for all the floors above it. The lowermost columns transfer the loads to the foundation, which, in turn, transfers them to the soil.

4.1.14 Falling Hazards Presence of various non-structural components such as air conditioning units, parapets and advertisement hoardings can cause injury to pedestrians as well as to building


32

occupants and contents during an earthquake, even though these may not have implications for the overall structural safety of the building. These are important because they can and do contribute to earthquake related losses as is evident from instances of chemical spills, breakage to building contents, misalignment of piping, etc. Falling hazards include mechanical and electrical equipment, piping and ducting, unsecured masonry parapets, and eccentrically placed water tanks on top of the building. A slab or a beam supported only on one side and projecting horizontally on the other side is called a 'Cantilever' slab or beam e.g. balconies, lofts and canopies. Figure 13 shows location of falling hazards in a building.

Figure 13. Falling hazards in a building

4.2 Phase-II: Preliminary Evaluation

Preliminary evaluation methodology is applied when in-depth evaluation of buildings

stock is required. In this stage, simplified analysis of the building under investigation is

performed based on a variety of methods.

This phase involves the following tasks:

Collection of drawings and redraw (if possible) in AutoCAD, Identification of the sizes of all columns and beams, Load calculations, Configuration related checks and strength related checks.


33

Phase-II can broadly classified into two categories, (a) configuration-related and (b)

strength related checks. The first tier involves a quick assessment of the earthquake

resistance of the building and its potential deficiencies, with the objective to screen out

the significantly vulnerable structures for the second tier detailed analysis and

evaluation. The first tier evaluation typically consists of assessing the configurationally

induced deficiencies known for unsatisfactory performance along with a few global

level strength checks, whereas the next level of evaluation consists of proper force and

displacement analysis to assess structural performance at both global and/or

component level.

Configuration related checks:

Although a building with an irregular configuration may be designed to meet all code requirements, irregular buildings generally do not perform as well as regular buildings in an earthquake. Typical building configuration deficiencies include an irregular geometry, a weakness in a given story, a concentration of mass, or a discontinuity in the lateral force resisting system. Vertical irregularities are defined in terms of strength, stiffness, geometry and mass. Horizontal irregularities involve the horizontal distribution of lateral forces to the resisting frames or shear walls. Load Path: Inertial forces, induced as a result of the seismic force effects from any horizontal direction, are transferred from the mass to the foundation through the load path. If there is a discontinuity in the load path, the building is unable to resist seismic forces regardless of the strength of the existing elements. Weak Story: The story strength is the total strength of all the lateral force-resisting elements in a given story for the direction under consideration. Weak stories are usually found where vertical discontinuities exist, or where member size or reinforcement has been reduced. The result of a weak story is a concentration of inelastic activity that may result in the partial or total collapse of the story. Soft Story: Soft story condition commonly occurs in buildings with open fronts at ground floor or with particularly tall first stories. Soft stories usually are revealed by an abrupt change in interstory drift. Effective Mass:


34

Mass irregularities can be detected by comparison of the story weights. The effective mass consists of the dead load of the structure tributary to each level, plus the actual weights of partitions and permanent equipment at each floor. Mass irregularities affect the dynamic response of the structure, and may lead to unexpected higher mode effects and concentrations of demand. Torsion: Whenever there is significant torsion in a building, the concern is for additional seismic demands and lateral drifts imposed on the vertical elements by rotation of the diaphragm. Buildings can be designed to meet code forces including torsion, but buildings with severe torsion are less likely to perform well in earthquakes.

Strength Related Checks:

The seismic evaluation documents specify some global level checks to quickly identify the major deficiencies. At the global level, buildings are mainly checked for shear stress and axial stress.

4.3 Phase-III: Detailed Evaluation It requires linear or nonlinear analyses of the building based on as-built dimensions. This phase involves the following tasks:

Calculation of vertical distribution of lateral forces by static method, Eccentricity calculation for additional torsional moment, Component level analysis of calculation of moment of resistance in hogging &

sagging, Check for shear capacity of beam, column flexural capacity, strong column weak

beam considerations, storey drift of the frame. Lastly, correlation will be drawn based on detailed evaluation and RVS score.

5. Seismicity of Himachal Pradesh Himachal Pradesh is located 31.1033° N, 77.1722° E and lies in the Himalayan Mountains, and is part of the Punjab Himalayas. Large earthquakes have occurred in all parts of Himachal Pradesh, the biggest being the Kangra Earthquake of 1905. The Himalayan Frontal Thrust, the Main boundary Thrust, the Krol, the Giri, Jutogh and Nahan thrusts lie in this region. However, it must be stated that proximity to faults does not necessarily translate into a higher hazard as compared to areas located further


35

away, as damage from earthquakes depends on numerous factors such as subsurface geology as well as adherence to the building codes. Chamba, Kullu, Kangra, Una, Hamirpur, Mandi, and Bilaspur Districts lie in Zone V. The remaining districts of Lahual and Spiti, Kinnaur, Shimla, Solan and Sirmaur lie in Zone IV. Since the earthquake database in India is still incomplete, especially with regards to earthquakes prior to the historical period (before 1800 A.D.). The largest instrumented earthquake in Himachal Pradesh was 1905 Kangra earthquake (Mw7.8). The seismicity and faults map of Himachal Pradesh is shown in figure 14.

6. Case study in Himachal Pradesh In this project, an attempt has been made to survey 9099 building in Himachal Pradesh. The above buildings include five varieties of buildings namely, brick masonry, reinforced concrete, hybrid, stone masonry and rammed earth buildings. The location of buildings considered in this analysis shown in figure 15. For each typology, RVS score is calculated from the above relations (Ref. section 4). From total number of buildings, the number of different typologies is as follows:

Reinforced Concrete Buildings: 1541 Brick Masonry Buildings: 4363 Stone Masonry Buildings: 1341 Rammed Earth Buildings: 518 Hybrid Buildings: 1318


36

Figure 14. Seismicity and location of faults in Himachal Pradesh state

Figure 15. Location of buildings considered in the analysis

The number of buildings surveyed in the districts of Bilaspur, Hamirpur, Kinnaur, Kullu, Lahul Spiti, Simla, Solan, Chamba, Kangra, Mandi, Sirmur and Una are 383, 789, 149, 619, 70, 401, 1553, 513, 1929, 692, 585, 637 respectively. The categorization of buildings according to district and status wise are shown in figure 16-31.


37

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Brick MasonryHybrid

Rammed EarthRC Frame

Stone Masonry

0

500

1000

1500

Districts

Types of Construction

Types of Construction

No

of

Bu

ild

ing

s

Figure 16. Statistics of type of construction for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Not UndertakenUndertaken

0

1000

2000

Quality of Maintenance

Districts

Quality of Maintenance

No

of

Bu

ild

ing

s

Figure 17. Statistics of quality of maintenance for 12 districts in HP state


38

UnaBilaspur

ChambaHamirpur

KangraKullu

MandiSimla

SirmurSolan

0-1010-20

20-3030-40

40-50>50

0

200

400

600

Districts

Age of Buildings

Age

No

of

Bu

ild

ing

s

Figure 18. Statistics of age of buildings for 10 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

HardMedium

SoftNot Sure

0

1000

2000

Districts

Soil Types

Soil Types

No

of

Bu

ild

ing

s

Figure 19. Statistics of type of soil conditions for 12 districts in HP state


39

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Does not ExistExists

0

1000

2000

Districts

Presence of Pounding

Presence of Pounding

No

of

Bu

ild

ing

s

Figure 20. Statistics of effect of pounding for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Does not Exist

Exists

Not Sure

0

500

1000

Districts

Corner Openings

Corner Openings

No

of

Bu

ild

ing

s

Figure 21. Statistics of corner openings for 12 districts in HP state


40

UnaBilaspur

ChambaHamirpur

KangraKullu

MandiSimla

SirmurSolan

Does not Exist

Exists

Not Sure

0

500

1000

Districts

Substantial openings

Substantial openings

No

of

Bu

ild

ing

s

Figure 22. Statistics of substantial openings for 10 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Does not ExistExists

0

1000

2000

Diaphragm Openings

Districts

Diaphragm Openings

No

of

Bu

ild

ing

s

Figure 23. Statistics of diaphragm action for 12 districts in HP state


41

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Exists

Does not Exist

Not Sure

0

500

1000

Districts

Horizontal Bands

Horizontal Bands

No

of

Bu

ild

ing

s

Figure 24. Statistics of horizontal bands for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

ExistsDoes not Exist

0

1000

2000

Soft Storey

Districts

Soft Storey

No

of

Bu

ild

ing

s

Figure 25. Statistics of soft storeys for 12 districts in HP state


42

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna


0

1000

2000

Heavy Overhangs

Districts

Heavy Overhangs

No

of

Bu

ild

ing

s

Figure 26. Statistics of heavy overhangs for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna


0

1000

2000

Short Column

Districts

Short Column

No

of

Bu

ild

ing

s

Figure 27. Statistics of short columns for 12 districts in HP state


43

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

Flat to MildMedium

SteepNot Sure

0

1000

2000

Districts

Slope

Slope

No

of

Bu

ild

ing

s

Figure 28. Statistics of buildings on slopes for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

ExistDoes not Exist

0

1000

2000

Staircase

Districts

Staircase

No

of

Bu

ild

ing

s

Figure 29. Statistics of existance of staircase in buildings for 12 districts in HP state


44

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUna

GoodModerate

Poor

0

500

1000

Districts

Quality of Construction

Quality of Construction

No

of

Bu

ild

ing

s

Figure 30. Statistics of construction quality for 12 districts in HP state

BilaspurChamba

HamirpurKangra

KinnaurKullu

LahulMandi

ShimlaSirmur

SolanUnaHorizontal

VerticalDiagonalHorz & Diag

Horz & VertHorz, Vert & Diag

Vert & DiagNo Cracks

0

200

400

600

800

Districts

Types of Cracks

Types of Cracks

No

of

Bu

ild

ing

s

Figure 31. Statistics of different type of cracks for 12 districts in HP state


45

In second stage, normal distribution curves are generated for different typology of buildings. In this project, a total of 9099 buildings are surveyed in Himachal Pradesh. The above buildings include five varieties of buildings namely, brick masonry, reinforced concrete, hybrid, stone masonry and rammed earth buildings. RVS scores have calculated for the above buildings. For brick masonry buildings the score ranges from 40 to 220 for 4141 buildings. For reinforced concrete buildings the score ranges from 50 to 160 for 1466 buildings. For hybrid buildings the score ranges from 60 to 140 for 1180 buildings. For stone masonry buildings the score ranges from 30 to 170 for 1042 buildings. For rammed earth buildings the score ranges from 50 to 150 for 509 buildings. The state Himachal Pradesh contains 12 districts namely, Bilaspur, Chamba, Hamirpur, Kangra, Kullu, Mandi, Simla, Sirmur, Solan, Una, Lahul Spitti, and Kinnaur. From the above data, RVS score is calculated for each district in Himachal Pradesh and plotted in QGIS. Normal distribution curves are generated based on available RVS scores. The normal distribution curves for total buildings as per district wise are shown in figure 32-37. From the above studies, it is clearly shown that all typology of buildings are available in the district of Kangra.

Reinforced concrete buildings:

From the study, the number of RC buildings is more in Kangra district. The normal distribution curves are wider for almost every district. Except Bilaspur district, the number of RC buildings is few in other districts. The mean of RVS score of all districts ranges from 100-110.

Brick Masonry buildings:

From the study, the number of brick masonry buildings is more in Bilaspur, Kangra, Una, Sirmur, Mandi and Hamirpur. The number of buildings present in these districts is more than 100. Few buildings are present in the rest of districts. The mean of RVS score of all districts ranges from 100-130. From the observation, brick masonry buildings are evenly distributed throughout the state.

Stone Masonry buildings: From the study, the number of stone masonry buildings is more in Kangra district. The normal distribution curves are wider for almost every district. Since the state is located in hilly terrain, stone masonry buildings are constructed in every district. The mean of RVS score of all districts ranges from 90-115.

Rammed earth buildings: From the study, the number of rammed earth buildings is more in Kangra district. The normal distribution curves are wider for almost every district. Except Kangra district, the number of rammed earth buildings is few in other districts. The mean of RVS score of all districts ranges from 95-115.


46

Hybrid buildings: From the study, the number of hybrid buildings is more in Kangra district. Since the normal distribution curve is narrow for Kangra district, the RVS score ranges from 60 to 140. Except Kangra, and Una, the distribution curve is wider for rest of districts. The mean of RVS score of all districts ranges from 100-110.

0 50 100 150 200 2500

50

100

150

200

250

300

350

400

450

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kullu

Mandi

Shimla

Sirmur

Solan

Una

Figure 32. Normal distribution curve for brick masonry buildings through RVS


47

40 60 80 100 120 140 1600

50

100

150

200

250

RVS Score

No

. o

f H

yb

rid

Bu

ild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 33. Normal distribution curve for Hybrid buildings through RVS

20 40 60 80 100 120 140 160 1800

50

100

150

200

250

300

RVS Score

No

. o

f R

am

me

d B

uild

ing

s

Chamba

Hamirpur

Kangra

Kullu

Mandi

Sirmur

Solan

Una

Figure 34. Normal distribution curve for Rammed earth buildings through RVS


48

0 50 100 150 2000

50

100

150

200

RVS Score

No

. o

f R

C B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 35. Normal distribution curve for RC buildings through RVS

0 50 100 150 2000

20

40

60

80

100

120

140

RVS Score

No

. o

f S

ton

e B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una


49

Figure 36. Normal distribution curve for Stone Masonry buildings through RVS

40 60 80 100 120 140 160 180 2000

200

400

600

800

1000

1200

1400

1600

1800

RVS Score

No

. o

f B

uild

ing

s

RC

Brick

Stone

Rammed

Hybrid

Figure 37. Normal distribution curve typology wise International Institute of Information Technology with collaboration of Taru consultancy has done survey on 47 buildings in Hamirpur, Kangra, Una, Mandi, Shimla and Sirmur districts of Himachal Pradesh state. For preliminary analysis, around 15 buildings are taken for further analysis. The summary of buildings surveyed is shown in table 1 and 2. The main criteria of selection of buildings are as follows: RVS score: The RVS score for all typology buildings is calculated from RVS forms

specified in appendix A. The buildings are selected based on low, medium and high RVS scores.

No. of storeys: The number of storeys varies from single storey to four storey. Unsymmetry: Building unsymmetry is also one of the factors which are considered

in the analysis. Around 5 asymmetric buildings are taken for analysis.


50

Table 1. Statistics of surveyed buildings in 6 districts of Himachal Pradesh

S. No District RC BM Hybrid Stone Traditional Total

1 Hamirpur 4 3 1 - - 8

2 Kangra 2 5 1 2 2 12

3 Una 2 3 - - - 5

4 Mandi 3 2 - - - 5

5 Shimla 4 5 1 - 1 11

6 Sirmur 3 2 1 - - 6

7 Total 18 20 4 2 3

Table 2. Details of surveyed buildings typology wise

S. No District Building Type No. of

Storeys RVS

Score

1 Hamirpur

(Seismic zone IV)

Brick Masonry 2 + Steel 113

Brick Masonry 2 110

Brick Masonry 1 83

Reinforced Concrete 2 125




Hybrid 1 118

2 Kangra

(Seismic zone V)

Brick Masonry 1 85

Brick Masonry 1 83

Brick Masonry 2 83

Brick Masonry 1 105

Brick Masonry 1 85



Hybrid 2 95

Stone Masonry 2 90

Stone Masonry 1 112

Rammed Earth 2 85

Rammed Earth 2 95

3 Una

(Seismic zone IV)

Brick Masonry 1 105

Brick Masonry 2 123

Brick Masonry 2 113




51

4 Mandi

(Seismic zone V)

Brick Masonry 3 52

Brick Masonry 1 85




5 Shimla

(Seismic zone IV)

Brick Masonry 2 85

Brick Masonry 4 35

Brick Masonry 1+truss 105

Brick Masonry 2 105

Brick Masonry 2+truss 82



Reinforced Concrete 1+truss 135


Hybrid 2+truss 105

Rammed Earth Truss 120

6 Sirmaur

(Seismic zone IV)

Brick Masonry 3 125

Brick Masonry 2 105


Reinforced Concrete 5+roof 90


Hybrid 4 120

Usually conclusions can be drawn based on the scores and Gaussian Normal

Distribution. It can be said that the buildings with higher performance scores perform better compared to lower performance scores shall get damaged. However the buildings which are in the middle range of performance score is large in number and drawing meaningful conclusion is a difficult task because of non-availability of standard results for the Indian conditions.

To overcome the above difficulty, it is proposed to do the preliminary assessment of selected buildings. For this purpose around 50 buildings falling in the range of mean plus or minus standard deviation are selected. Later detailed analysis is required on selected few buildings to standardize the RVS score. After standardization of the performance scores, the fragility curves will be prepared. The fragility curve is the graph between seismic ground acceleration in ‘g’ and damage. This relationship will estimate loss for different categories of buildings and intensities of earthquakes. The normal distribution curves are drawn for all typology of buildings in the state of Himachal Pradesh. The database of buildings for Himachal Pradesh is provided by TARU Consultants Ltd. The total number of buildings present in the state is as follows:


52

Reinforced Concrete Buildings: 8,426 Brick Masonry Buildings: 4,39,889 Stone Masonry Buildings: 3,29,911 Rammed Earth Buildings: 2,16,916 Hybrid Buildings: 32,646 Total Number of Buildings: 1027788 The normal distribution curves for the state of HP are shown in figure 38-43.

0 50 100 150 2000

100

200

300

400

500

600

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 38. Normal distribution curve for RC buildings


53

0 50 100 150 200 2500

1

2

3

4

5

6

7x 10

4

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 39. Normal distribution curve for Brick buildings

0 50 100 150 2000

1

2

3

4

5

6

7

8

9x 10

4

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 40. Normal distribution curve for Stone buildings


54

20 40 60 80 100 120 140 160 1800

2

4

6

8

10

12x 10

4

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 41. Normal distribution curve for Rammed Earth buildings

40 60 80 100 120 140 1600

2000

4000

6000

8000

10000

RVS Score

No

. o

f B

uild

ing

s

Bilaspur

Chamba

Hamirpur

Kangra

Kinnaur

Kullu

Lahul

Mandi

Shimla

Sirmur

Solan

Una

Figure 42. Normal distribution curve for Hybrid buildings


55

40 60 80 100 120 140 160 180 2000

0.5

1

1.5

2

2.5

3

3.5

4

4.5x 10

5

RVS Score

No

. o

f B

uild

ing

s

RC

Brick

Stone

Rammed

Hybrid

Figure 43. Normal distribution curve typology wise

7. Conclusions An attempt has been made to do rapid visual screening of five varieties of

buildings in Himachal Pradesh state. RVS score has calculated for 9099 buildings and plotted normal distribution curves for each typology of building to understand the distribution of buildings in HP state. From the study, it is clearly shown that Kangra district have more buildings in all five different typologies.

Results of the performance scores reveal that around 17% (1541 out of 9099) of buildings are reinforced concrete, 48% (4363 out of 9099) of buildings are brick masonry, 15% (1341 out of 9099) of buildings are stone masonry, 5% (518 out of 9099) of buildings are rammed earth and 15% (1318 out of 9099) of buildings are hybrid in the whole state of Himachal Pradesh. However, there are some low RVS score buildings which are potentially vulnerable to future earthquakes. Also it is suggested that preliminary analysis needs to be performed on 47 buildings and detailed analysis for 15 buildings for calibrating RVS scores. Finally all the buildings will be categorized in a few performance factors categories. After developing the fragility curves for the region, damage due to different ground acceleration of earthquakes will be estimated.

Recommendations


56

1. Implementation of the building code regulations for rammed earth, hybrid and stone masonry buildings needs to be initiated in our country.

2. Structural detailing particularly near the beam-column junctions must be improved with adequate shear reinforcement being provided.

3. Performance of the low-rise buildings constructed using locally available materials must be improved. This factor could lead to a significant reduction of casualties in future earthquakes.

4. Research is needed to investigate and improve the performance of the above buildings.

Acknowledgment

The authors would like to express their gratitude to the TARU Leading Edge Private Limited, New Delhi.

8. References

1. Jain S.K., (2005), “The Indian Earthquake Problem”, Current Science, Vol.89 (9), pp. 1464-1466.

2. Keya Mitra (2008), “Assessing Urban Fabric Against Natural Disasters: A Case

Study of Seismic Vulnerability of Kolkata”, Ph.D Thesis, Department of Architecture, Town and Regional Planning, Bengal Engineering and Science

University, Shibpur, India.

3. Singh P., (2005), “Population Vulnerability for Earthquake Loss Estimation using

Community Based Approach with GIS: Urban Infrastructure Management”, Master of Science, International Institute for Geo Information Science and Earth

Observation, Netherlands.

4. FEMA 154, 1988. Rapid Visual Screening of Buildings for Potential Seismic

Hazards - A Handbook, Federal Emergency Management Agency, Washington

D.C.

5. FEMA 154/July, 1988. ATC-21, Rapid visual screening of buildings for potential

seismic hazards: A handbook, Applied Technology Council, CA.

6. FEMA 310, 1998. Handbook for the Seismic Evaluation of Buildings -A

Prestandard, Federal Emergency Management Agency, Washington D.C.


57

7. Srikanth Terala and Pradeep Kumar Ramancharla, (2010), “Rapid Visual Survey

of Existing Buildings in Gandhidham and Adipur Cities, Kachchh, Gujarat”,

Proc. of International Symposium on the 2001 Bhuj Earthquake and Advances in

Earthsciences and Engineering, Gujarat, India.

Rapid Visual Screening for Seismic Evaluation of...

Documents

Transcript of Rapid Visual Screening for Seismic Evaluation of...