Page | 1

RETROFITTING PROCESS OF EXISTING BUILDING WITH

RESPECT TO SEISMIC CONSIDERATION IN BANGLADESH

AYESHA BINTA ALI

MUNSHI MD. RASEL

MD. MOINUL ISLAM

MD. ASIF RAHMAN

DEPARTMENT OF CIVIL ENGINEERING

AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY

APRIL 2013

Page | 2

RETROFITTING PROCESS OF EXISTING BUILDING WITH

RESPECT TO SEISMIC CONSIDERATION IN BANGLADESH

A Thesis

Submitted by

Ayesha Binta Ali Student No.: 10.01.03.033

Munshi Md. Rasel Student No.: 10.01.03.075

Md. Moinul Islam Student No.: 10.01.03.076

Md. Asif Rahman Student No.: 10.01.03.108

In partial fulfillment of the requirements for the degree of

Bachelor of Science in Civil Engineering

Under the supervision of

Dr. Md. Mahmudur Rahman

Professor

Department of Civil Engineering

AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY

April 2013

Page | 3

DECLARATION

We declare that the topics material which is presented in this thesis paper is the outcome

of our hard work. We also declare that neither this paper nor any complete part of it is

being submitted elsewhere for any other purpose to award of any degree. Where other

sources are used, appropriate references are made.

……………………………………. …………………………………

Ayesha Binta Ali Munshi Md. Rasel

(10.01.03.033) (10.01.03.075)

……………………………………. …………………………………

Md. Moinul Islam Md. Asif Rahman

(10.01.03.076) (10.01.03.108)

I do hereby agree to the approach and content of the present exposition.

………………………………….

Dr. Md. Mahmudur Rahman

Professor

Department of Civil Engineering

AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY

April 2013

Page | 4

ACKNOWLEDGEMENT

First of all we would like to express our sincere gratitude to the Almighty Allah for

giving us this opportunity and enabling to complete the task peacefully.

We would like to express our sincere gratitude and indebtedness to our thesis supervisor

Dr. Mahmudur Rahman, Department of Civil Engineering, Ahsanullah University of

Science and Technology, for providing us excellent guidance and continuous assistance

throughout the study. His constant criticism, advice, assertions, appreciation were very

vital and irrevocable. Without his motivation it wouldn’t have been possible for us to

finish our paper. We have received endless support and guidance from him, right from

the development of ideas, methodology of work and this presentation. We are thankful

to him for his encouragement throughout the study.

We would also like to thank all of the faculty members specially A.S.M. Fahad Hossain,

Lecturer and Md. Mashfiqul Islam, Assistant Professor of Civil Engineering

Department, who also have provided us valuable guidance, unstinted support and

endless encouragement in this study. Indeed this page of acknowledgement shall never

be able to touch the horizon of generosity of those who tendered their help to us.

Page | 5

ABSTRACT

There might be many buildings in Bangladesh which do not meet the current seismic

requirement and as a result may suffer much damage during the earthquake. Especially

the older buildings which were constructed without the consideration of proper seismic

forces should be evaluated for seismic load and retrofitted accordingly. If remedial

measures are taken based on seismic evaluation, much damage can be overcome. In this

research study, a typical existing building in Dhaka city constructed before 1990 is

considered for seismic evaluation.

The objective of the research here is to evaluate the existing building for earthquake

performance. For applying earthquake loads, Equivalent Static Force Method is used

according to BNBC 1993. Reinforcement details of our considered building were not

available. For the purpose of study, in the first step an analysis is done applying only

Dead and Live Loads according to BNBC 1993. The building is then designed for Dead

Load and Live Load only without the consideration of seismic or wind load. In the

second step, the building is analyzed for seismic loading in addition to Dead Load and

Live Load with proper load factor. Three dimensional analyses is done using design

software STAAD-Pro. The Demand Capacity Ratio (DCR) is carried out for beams and

columns in order to evaluate the member for seismic loads. DCR is the ratio between

the Demand and Capacity where Demand is the amount of force or deformation

imposed on an element or component and Capacity is the permissible strength or

deformation of a structural member or system. From the Demand obtained from step-2

and Capacity from step-1, DCR is calculated. If Demand is more than Capacity, the

member is considered failed and vice versa. Then retrofitting is carried out for the failed

Page | 6

beams and columns. Steel Plating Retrofitting Method is applied for the beams and

Concrete Jacketing Retrofitting Method is applied for the columns. The comparisons

between Static and Dynamic behavior are also shown in this paper.

It is found that a number of beams and columns failed when seismic load is applied to

the structure. It is recommended that the buildings which were not built with seismic

consideration can be evaluated and retrofitted following the thesis procedure presented

in this study.

Page | 7

CONTENTS

Title Page

Declaration i

Acknowledgement ii

Abstract iii

Contents v

List of Figures ix

List of Tables xii

CHAPTER 1: INTRODUCTION 1

1.1: General 2

1.2: Earthquake in Bangladesh 3

1.2.1: Geometric Position and Tectonic Plates 3

1.2.2: Building Collapse Due to Shoddy Construction in Bangladesh 7

1.3: Objective of the Study 12

1.4: Scope of the Study 13

1.5: Necessity of Seismic Evaluation 14

Page | 8

CHAPTER 2: REVIEW OF LITERATURE 16

CHAPTER 3: METHODOLOGY 26

3.1: General 27

3.2: Seismic Evaluation 28

3.3: Seismic Retrofitting 32

3.3.1: Steel Plating 33

3.3.2: Concrete Jacketing 34

CHAPTER 4: BUILDING GEOMETRY AND MANUAL

STRUCTURAL ANALYSIS 38

4.1: General 39

4.2: Load Analysis and Design without Seismic Load 42

4.2.1: Design of Slab 42

4.2.2: Design of Beam 45

4.2.3: Design of Column 49

4.2.4: One Way Slab Design 55

4.3: Seismic Load Calculation 56

Page | 9

CHAPTER 5: 3D STRUCTURAL SOFTWARE ANALYSIS AND

RETROFITTING 65

5.1: General 66

5.2: Geometric Model and Design Parameters 67

5.3: Loads 70

5.4: Check for Beams 74

5.5: Check for Columns 79

5.6: Retrofitting 84

5.6.1: Retrofitting of Beam by Steel Plating 84

5.6.2: Retrofitting Of Column by Concrete Jacketing 86

5.7: Dynamic Analysis (Time History Analysis) 93

5.7.1: Introduction to EL-CENTRO COMP S90W Ground Motion 93

5.7.2: Structural Models and Their Top Floor Time History Displacement 95

5.7.3: Comparison of Displacements of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 96

5.7.4: Comparison of Story Drifts Of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 98

5.7.5: Comparison of Story Moment of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 100

Page | 10

CHAPTER 6: CONCLUSION AND RECOMMENDATION 102

CHAPTER 7: REFERENCES 105

Page | 11

LIST OF FIGURE

Title Page

Figure 1.2.1: Regional Tectonic Setup of Bangladesh With Respect To Plate

Configuration 4

Figure 1.2.2: Digital Elevation Model (DEM) Of Bangladesh and Surroundings

Showing Geological Faults – Potential Sources of Major Earthquakes in Bangladesh

5

Figure 1.2.3: Seismic Zone of Bangladesh 6

Figure 1.2.4: Building Collapse in Christchurch Earthquake 10

Figure 1.2.5: Building Collapse in Turkey 11

Figure 1.2.6: Building Collapse in Mexico City 12

Figure 3.3.1: Jacketing of RC Columns 36

Figure 4.1.1: Layout of Plan 40

Figure 4.1.2: Layout of Plan with Grid Line 41

Figure 5.2.1: Plan of Building 67

Figure 5.2.2: Side View of Building 67

Figure 5.2.3: Whole Building with Member Properties Applied To All the Members (3-

D View) 68

Page | 12

Figure 5.3.1: Dead Load on Building 71

Figure 5.3.2: Dead Load on First Floor (Load of Walls on Beam + Self-Wt.) 72

Figure 5.3.3: Dead Load on First Floor (Floor Finish + Self-Wt.) 72

Figure 5.3.4: Live Load on Building 73

Figure 5.3.5: Live Load on first Floor 74

Figure 5.4.1: Concrete Design of Beam in STAAD Pro 75

Figure 5.4.2: Beam of First Floor Eligible for Steel Plating 79

Figure 5.5.1: Concrete Design of Column in STAAD Pro 81

Figure 5.5.2: Column Eligible for Concrete Jacketing 84

Figure 5.6.1: Concrete Jacketing of Exterior Column A2 87

Figure 5.6.2: Concrete Jacketing of Interior Column B3 88

Figure 5.6.3: Concrete Jacketing of Corner Column A1 90

Figure 5.6.4: Concrete Jacketing of Corner Column A1 91

Figure 5.7.1: EL-CENTRO COMP S90W Ground Motion with PGA Scaled To 0.21g

and Duration Equal to 47.56 Seconds 94

Figure 5.7.2: Time History Displacement of the Highlighted Node of Structure 95

Figure 5.7.3: Comparison of Displacements along Z-Direction between Dynamic and

Static Earthquake Analysis 97

Page | 13

Figure 5.7.4: Comparison of Story Drift along Z-Direction between Dynamic and

Static Earthquake Analysis 99

Figure 5.7.5: Comparison of Story Moment along Z-Direction between Dynamic and

Static Earthquake Analysis (A4 column) 101

Page | 14

LIST OF TABLE

Title Page

Table 1.2.1: Seismic Zoning of Bangladesh 6

Table 4.1: Column Dimensions 39

Table 4.2.1: Slab Load Calculation 43

Table 4.2.2: Moment Calculation of Slabs 44

Table 4.2.3: Beam Load Calculation 47

Table 4.2.4: Column Load Calculation 54

Table 4.3.1: Seismic Load Calculation for Each Grid 58

Table 4.3.2: Total Seismic Load Calculation 62

Table 5.2.1: Column Dimensions 69

Table 5.4.1: Level 01 Beam Check with Seismic Loads 77

Table 5.4.2: Level 01 Beam Check without Seismic Loads 78

Table 5.5.1: Parameters for Column Check 80

Table 5.5.2: Column Check 82

Table 5.6: Concrete Jacketing 92

Table 5.7.1: Comparison of Displacements of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 96

Page | 15

Table 5.7.2: Comparison of Story Drifts of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 98

Table 5.7.3: Comparison of Story Moment of Different Floors of Structure between

Dynamic and Static Earthquake Analysis 100

Page | 16

CHAPTER 1

INTRODUCTION

Page | 17

1.1: General

An earthquake (also known as a quake, tremor or temblor) is the result of a sudden

release of energy in the Earth’s crust that creates seismic waves. The seismicity or

seismic activity of an area refers to the frequency, type and size of earthquakes

experienced over a period of time. In most general sense, the word earthquake is used

to describe any seismic event — whether natural or caused by humans — that generates

seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also

by other events such as volcanic activity, landslides, mine blasts, and nuclear tests.

Earthquakes are measured using observations from seismometers. The moment

magnitude is the most common scale on which earthquakes larger than approximately

5 are reported for the entire globe. The more numerous earthquakes smaller than

magnitude 5 reported by national seismological observatories are measured mostly on

the local magnitude scale, also referred to as the Richter scale.

The buildings which do not fulfill the requirements of seismic design, may suffer

extensive damage or collapse if shaken by a severe ground motion. Seismic Evaluation

and Retrofit of existing buildings describes deficiency-based and systematic procedures

that use performance-based principles to evaluate and retrofit existing buildings to

withstand the effects of earthquakes.

In this research an existing building is evaluated for earthquake performance. For

applying earthquake loads, Equivalent Static Force Method is used according to BNBC

1993. Reinforcement details of our considered building were not available. For the

purpose of study, in the first step an analysis is done applying only Dead and Live Loads

Page | 18

according to BNBC 1993. The building is then designed for Dead Load and Live Load

only without the consideration of seismic or wind load. In the second step, the building

is analyzed for seismic loading in addition to Dead Load and Live Load with proper

load factor. Three dimensional analyses is done using design software STAAD-Pro.

The Demand Capacity Ratio (DCR) is carried out for beams and columns in order to

evaluate the member for seismic loads. DCR is the ratio between the Demand and

Capacity where Demand is the amount of force or deformation imposed on an element

or component and Capacity is the permissible strength or deformation of a structural

member or system. From the Demand obtained from step-2 and Capacity from step-1,

DCR is calculated. If Demand is more than Capacity, the member is considered failed

and vice versa. Then retrofitting is carried out for the failed beams and columns. Steel

Plating Retrofitting Method is applied for the beams and Concrete Jacketing

Retrofitting Method is applied for the columns. The comparisons between Static and

Dynamic behavior are also shown in this paper.

1.2: Earthquake in Bangladesh

1.2.1: Geometric Position and Tectonic Plates

Bangladesh, a densely populated country in South Asia, is located in the northeastern

part of the Indian sub-continent at the head of the Bay of Bengal. Tectonically,

Bangladesh lies in the northeastern Indian plate near the edge of the Indian carton and

at the junction of three tectonic plates – the Indian plate, the Eurasian plate and the

Burmese micro plate. These form two boundaries where plates converge– the India-

Eurasia plate boundary to the north forming the Himalaya Arc and the India-Burma

plate boundary to the east forming the Burma Arc.

Page | 19

Figure 1.2.1: Regional Tectonic Setup of Bangladesh With Respect To Plate

Configuration.

Bangladesh is surrounded by the regions of high seismicity which include the

Himalayan Arc and SHILLONG PLATEAU in the north, the Burmese Arc, Arakan Yoma

anticlinorium in the east and complex Naga-Disang-Jaflong thrust zones in the

northeast. It is also the site of the Dauki Fault system along with numerous subsurface

active faults and a flexure zone called Hinge Zone. These weak regions are believed to

provide the necessary zones for movements within the basin area.

Page | 20

Figure 1.2.2: Digital Elevation Model (DEM) Of Bangladesh and Surroundings

Showing Geological Faults – Potential Sources of Major Earthquakes in Bangladesh.

The 1993 Bangladesh National Building Code provides guidelines for earthquake

resistant design. On the basis of distribution of earthquake epicenters and morph

tectonic behavior of different tectonic blocks Bangladesh has been divided into three

generalized seismic zones. The northeastern folded regions of Bangladesh are the most

active zones and belong to the zone-I. The seismic coefficient of this zone is 0.075. The

zone II consists of the regions of recent uplifted Pleistocene blocks of the Barind and

Madhupur and the western extension of the folded belt and the coefficient for this zone

Page | 21

is 0.15. The southwest Bangladesh is seismically quiet zone and represented by zone

III with coefficient 0.25. Ground condition (firm or soft) has not been taken into

consideration during the seismic zonation of Bangladesh. Characteristic features of

seismic zonation of Bangladesh are presented in the Table 1.2.1.

Table 1.2.1: Seismic Zoning of Bangladesh

Zoning Area Mercalli Scale

I North and eastern regions of Bangladesh (Seismically most

active)

II Lalmai, Barind, Madhupur Tracts, Dhaka, Comilla, Noakhali

and western part of Chittagong Folded belt.

III Khulna division S-E Bangladesh (Seismically relatively

quiet)

Figure 1.2.3: Seismic Zone of Bangladesh.

Page | 22

Dhaka is surrounded by the old Brahmaputra floodplain in the north and east, by the

Ganges-Meghna flood plain in the south and by the Jamuna flood plain in the west.

Dhaka is slightly elevated above the surrounding floodplains and represents mostly flat

land with minor undulations. Topographically Dhaka is of low relief with many low

depressions. According to Alam (1988), the Madhupur Tract is structurally controlled.

The Pleistocene sediments of Madhupur Tract have been affected by numerous

episodes of faulting. These faults are probably the branch out surface faults from the

low dipping western extension of Burma Arc detachment fault. Dhaka lies within 50 to

500 km distances from the seism genic faults and sits on the Burma Arc detachment

fault. Dhaka city falls in seismic zone II of the seismic zoning map of Bangladesh.

1.2.2: Building Collapse Due to Shoddy Construction in

Bangladesh

The construction industry of Bangladesh is not quite good. Here workmanship of

worker is low and also many owner and construction contractors are looking for cheap,

low quality work for more savings. Many building of the major cities like Dhaka and

Chittagong were constructed and still constructing disobeying rules of local and

government authority.

Rana plaza incident can be considered here. Officials have blamed the collapse on

shoddy construction methods. The upper four floors of the plaza, for example, were

reportedly constructed illegally without permits, and a crack was seen on the building

exterior a day before the collapse. The building was not built in compliance with the

[safety] rules and regulations. These types of accidents are a common problem in

Page | 23

developing countries, where construction materials can be expensive and building

inspections infrequent.

Uneven Footing

Henri Gavin, a civil and environmental engineer at Duke University, speculated that

the building's foundation was substandard. It could be that one edge of the building was

on much softer soil than the other, so that part of the building settled down a little bit

more. That could easily lead to an instability that would precipitate a collapse.

Another possibility is that weight on the top factory floors—where the crack was

spotted—was unevenly distributed.

When designing a building, engineers are supposed to consider different combinations

of how loads are placed in the structure. The intention is to require the engineer to

consider as many cases as possible. Such modeling is easy to do—if one has the right

computer and software. In developing countries such as Bangladesh, however,

calculating different load distributions can be a time-consuming process, and as a result

might be skipped.

Construction Problems

Poor building design is only one part of the problem, however. The best building design

in the world is for naught if a construction firm doesn't follow the plans precisely. That

may have been the case with Rana Plaza, which appears to have been built largely out

of concrete.

Page | 24

Concrete buildings require large amounts of reinforcing steel, called rebar, to prevent

excessive cracking. Depending on the country, steel can be costly. “In developing

countries, steel is relatively expensive in comparison to the labor and concrete," said

Dan Jansen, a civil engineer at California Polytechnic State University. But in

developing countries, less steel is often used than is recommended because of the cost.

Reducing or changing the reinforcing steel without the building official's approval is

never acceptable. But enough rebar was not used in Rana Plaza. So the amount of

reinforcing steel used didn't allow it to transfer the load from one section to another. In

addition to possibly being under-reinforced, the concrete mix may not have had enough

cement. Investigations following this earthquake revealed that the concrete had more

sand and less cement than required by typical design standards.

A Fatal Crack

A crack in a concrete building by itself is not necessarily a cause for alarm. There's a

saying: There are two kinds of concrete, there's cracked concrete and concrete that

hasn't cracked yet. Cracks are not a cause for concern unless you can see it moving over

time or it seems to be excessive.

The number one thing that structural engineers in the U.S. are trying to avoid is sudden,

catastrophic failure. We design structures to fail, but they must fail in a controlled

manner. Concrete structures that include an adequate amount of rebar are more likely

to yield in a ductile behavior, rather than folding like a deck of cards.

If Rana Plaza lacked redundancy because it was built with insufficient rebar, then the

building would have been a disaster waiting to happen.

Page | 25

It also appears as if sections of the plaza were still under construction when the disaster

happened. Some floors lacked walls, for example, and exposed columns with

protruding rebar are visible on the upper levels. It looks like the building was partially

built and used. Occupying a building under construction is just a recipe for disaster.

This building was used as garments factories of several owners with markets and office

spaces for institutions like bank etc. Being commercial building, to have uninterrupted

electricity supply, several generator were used there. BGMEA confirmed that during

collapse 3122 workers were working and a total 5000 workers were employed in

different floors of garments factories.

Figure 1.2.4: Building Collapse in Christchurch Earthquake.

Page | 26

The image above is taken from the collapse in Christchurch earthquake, which

resembles somewhat to Rana plaza. The difference is that there was a release of huge

strain energy due to deformation of plate boundary below South Islands (Australian

plate and Pacific plate). The energy released by this earthquake was 6.3 (in magnitude

scale). In Savar not such agitation was felt. The structure was collapsed due to service

loads, unexpected vibrations and its own weight.

Figure 1.2.5: Building Collapse in Turkey.

This image above is taken from Erics, Turkey; this failure seems more close to Savar

collapse. But this collapse was also associated with an earthquake of magnitude 7.1.

Page | 27

Figure 1.2.6: Building Collapse in Mexico City.

The last figure above is taken from Mexico City. Here we can notice that bottom five

floors were sandwiched. But this was due to one the great earthquake of the world;

Magnitude 8.1 Mexico earthquake. The bottom floors had mass irregularity and

sandwiched.

1.3: Objective of the Study

The main objective of this study is to assess the seismic vulnerability of an existing RC

structure and to provide for retrofit in case the members fail. The comparison between

Static and Dynamic behavior of the structure are also shown in this paper.

Page | 28

The objectives of this research paper are:

To design the structure considering only Dead Load and Live Load

To create the model of the structure using STAAD Pro and applying Seismic

Load

To compute the DCR (Demand to Capacity Ratio)

To provide retrofit for the failed members- Steel Plating for beams and Concrete

Jacketing for columns

To show the comparison between Static and Dynamic behavior for the structure

1.4: Scope of the Study

The building under study in this project is an existing multi-storied residential building

in Dhaka City. Since the reinforcement details of the building were not available, so

that a design is prepared applying only Dead Load and Live Load according to BNBC

1993. In the Equivalent Static procedure of seismic analysis, the Seismic Loads are

applied to the center of mass of the story, but in STAAD Pro it is assumed that the

Seismic Loads to be nodal loads and applied it to nodes dividing the total lateral story

loads in equal proportion per node and not at the exact center of mass of the story. While

considering retrofit measures for the structure, Concrete Jacketing and Steel Plating are

applied. It is assumed that there would be sufficient adhesion between plates and

concrete so that there is no failure due to bonding.

1.5: Necessity of Seismic Evaluation

Page | 29

It is known that damaging earthquakes are very often followed by a series of aftershocks

and sometimes by other main shocks. Past earthquakes have shown that when urban

areas are hit by damaging earthquakes, a significant percentage of structures attain light

to moderate damage. Moreover, it is known that structures that sustained some damages

prior to seismic event may collapse during a succeeding event. Such unfortunate events

have claimed many lives. Therefore, these structures impose a potential risk to human

life, economic assets and the environment. Thus, making decisions regarding the post-

earthquake functionality and repair of the damaged structures is a critical part of the

post-earthquake recovery process. Also, from the effects of significant earthquakes that

has struck the different parts of country, it is concluded that the seismic risks in urban

areas are increasing and are far from socio-economically acceptable levels. Therefore

there is an urgent need to reverse this situation and it is believed that one of the most

effective ways of doing this is through: (1) The seismic evaluation of existing stuck off

structures. (2) The development of more reliable seismic standards and code provisions

than those currently available with their stringent implementation for the complete

engineering of new engineering facilities. Therefore, an accurate estimation of the

performance of structure during an earthquake is crucial for estimating the actual effects

of that earthquake on the existing RC structures.

The vulnerability of the structure can be assessed with a higher accuracy and better

informed decisions can be made on the possible improvement of the seismic resistance

of existing RC structures. For example, the critical components of the structure that are

likely to sustain significant damages during future earthquake ground motions may be

identified. Accordingly, the required immediate structural interventions may be

designed to reduce the deformation demands on these components. Subsequently, the

Page | 30

overall behavior of the structure may be improved to achieve a satisfactory overall

seismic performance during a future earthquake.

CHAPTER 2

Page | 31

REVIEW OF LITERATURE

Prior to the introduction of modern seismic codes in the late 1960s for developed

countries (US, Japan etc.) and late 1970s for many other parts of the world (Turkey,

China etc.),many structures were designed without adequate detailing and

reinforcement for seismic protection. In view of the imminent problem, various

Page | 32

research works has been carried out. State-of-the-art technical guidelines for seismic

assessment, retrofit and rehabilitation have been published around the world - such as

the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s

guidelines

For many older facilities, one mitigation option to protect against seismic hazards is the

seismic rehabilitation of existing structural elements. An example of the benefit of such

mitigation measures can be found through an analysis of the case of North Hall at the

University of California at Santa Barbara. The North Hall facility is a three-story

reinforced concrete structure, designed and built in 1960. It was originally thought that

the building was designed to the 1958 seismic load resistance building code, which did

not prescribe the more modern types of earthquake resistant construction. However, a

1973 engineering investigation discovered that the building was instead designed for

only one-tenth of the 1958 requirements, creating unsafe conditions at the facility.

Fortunately, the construction work to correct the original design errors occurred at about

the same time that the Uniform Building Code was being revised to include substantial

earthquake resistance provisions. The facility was partially rebuilt in 1975 by adding

interior and exterior shear walls to provide additional seismic resistance. The decision

was then made to rebuild the structure according to the provisions of the revised

building code; the upgrade made the North Hall Building the only building on campus

built to that advanced level of seismic standards.

Chandrasekaran and Rao (2002) investigated the design of multi- storied RCC buildings

for seismicity. Reinforced concrete multi-storied buildings are very complex to model

Page | 33

as structural systems for analysis. Usually, they are modeled as two-dimensional or

three-dimensional frame systems using finite beam elements. However, no guidelines

are available for the rational computation of sectional properties incorporating the

effects of reinforcements in concrete members and the analysis is full of

approximations.

Shunsuke Otani (2004) studied earthquake resistant design of RCC Buildings (Past and

Future). This paper briefly reviews the development of earthquake resistant design of

buildings. Measurement of ground acceleration started in 1930’s, and the response

calculation was made possible in 1940’s. Design response spectra were formulated in

the late 1950’s to 1960’s. Non-linear response was introduced in seismic design in

1960’s and the capacity design concept was introduced in 1970’s for collapse safety.

The damage statistics of RCC buildings in 1995 Kobe disaster demonstrated the

improvement of building performance with the development of design methodology.

Buildings designed and constructed using outdated methodology should be upgraded.

Performance basis engineering should be emphasized, especially for the protection of

building functions following frequent earthquakes.

Durgesh C. Rai (2005) gave the guidelines for seismic evaluation and strengthening of

buildings. This document is developed as part of project entitled ―Review of Building

Codes and Preparation of Commentary and Handbooks‖ awarded to Indian Institute

of Technology Kanpur by the Gujarat State Disaster Management Authority (GSDMA),

Gandhinagar through World Bank finances. This document is particularly concerned

Page | 34

with the seismic evaluation and strengthening of existing buildings and it is intended

to be used as a guide.

Another thesis paper was presented by Prof. Pravin B. Waghmare of Acharya

Shrimannarayan (2005), Polytechnic Pipri (M)- Wardha-Maharashtra entitled “A

Comparative Study of Retrofitting Of R.C. Building Using Steel Bracing And Infill Walls”

.The objective of his study was to identify an efficient retrofitting method for existing

open ground story reinforced concrete frame buildings. Failure of several soft-stored

buildings in the past earthquakes underscores the need to retrofit existing soft-story

buildings. During the Bhuj (Gujarat) earthquake of 6thJanuary 2001 several soft

storied building failed there by confirming the vulnerability of such buildings to

earthquake loading. That underscores the need to retrofit existing soft story buildings

to prevent their total collapse. The existing building structures, which were designed

and constructed according to early coda provisions, do not satisfy requirements of

current seismic code and design practices. A two dimensional R.C. frame designed

with linear elastic dynamic analysis using response spectrum method. The computer

software package STAAD Pro–2005 was used for dynamics analysis technique was

used to assess the performance of a (G + 4) reinforced concrete buildings, of which

the ground story was a parking facility the ground story was 3.5m high while the upper

stories giving a total height of 15.5 m. the building was located in Seismic Zone IV.

Devesh et al. (2006) agreed on the increase in drift demand in the tower portion of

set-back structures and on the increase in seismic demand for buildings with

Page | 35

discontinuous distributions in mass, strength and stiffness. The largest seismic

demand was found for the combined stiffness and strength irregularity.

It was found out that seismic behavior is influenced by the type of model.

Sadjadi et al. (2007) presented an analytical approach for seismic assessment of RC

frames using nonlinear time history analysis and push-over analysis. The analytical

models were validated against available experimental results and used in a study to

evaluate the seismic behavior of these 5-story frames.

It was concluded that both the ductile and the less ductile frames behaved very well

under the earthquake considered, while the seismic performance of the GLD structure

was not satisfactory. The retrofitted GLD frame had improved seismic performance.

Lee and Ko (2007) subjected three 1:12 scale 17-story RC wall building models having

different types of irregularity at the bottom two stories to the same series of simulated

earthquake excitations to observe their seismic response characteristics. The first

model had a symmetrical moment-resisting frame (Model 1), the second had an in

filled shear wall in the central frame (Model 2), and the third had an in filled shear wall

in only one of the exterior frames (Model 3) at the bottom two stories. The total

amounts of energy absorption by damage are similar regardless of the existence and

location of the in filled shear wall. The largest energy absorption was due to

overturning, followed by the shear deformation.

Karavasilis et al. (2008) studied the inelastic seismic response of plane steel moment-

resisting frames with vertical mass irregularity. The analysis of the created response

Page | 36

databank showed that the number of stores, ratio of strength of beam and column

and the location of the heavier mass influence the height-wise distribution and

amplitude of inelastic deformation demands, while the response does not seem to be

affected by the mass ratio.

Athanassiadou (2008) concluded that the effect of the ductility class on the cost of

buildings is negligible, while performance of all irregular frames subjected to

earthquake appears to be equally satisfactory, not inferior to that of the regular ones,

even for twice the design earthquake forces. DCM frames were found to be stronger

and less ductile than the corresponding DCH ones. The over strength of the irregular

frames was found to be similar to that of the regular ones, while DCH frames were

found to dispose higher over strength than DCM ones. Pushover analysis seemed to

underestimate the response quantities in the upper floors of the irregular frames.

Kim and Elnashai (2009) observed that buildings that are seismically designed to

contemporary codes would have survived the earthquake. But, the vertical motion

would have significantly reduced the shear capacity in vertical members.

Abu Lego (2010) studied the Design of earthquake resistant building using Site

Response spectra method. According to the Indian standard for Earthquake resistant

design (IS: 1893), the seismic force depends on the zone factor (Z) and the average

response acceleration coefficient (Sa/g) of the soil types at thirty meter depth with

suitable modification depending upon the depth of foundation. In the present study an

attempt has been made to generate response spectra using site specific soil parameters

Page | 37

for some sites in seismic zone V, i.e. Arunachal Pradesh and Meghalaya and the

generated response spectra is used to analyze some structures using commercial

software STAAD Pro.

Sarkar et al. (2010) proposed a new method of quantifying irregularity in vertically

irregular building frames, accounting for dynamic characteristics (mass and stiffness).

The salient conclusions were as follows:

(1)A measure of vertical irregularity, suitable for stepped buildings, called ‗regularity

index‘, is proposed, accounting for the changes in mass and stiffness along the height

of the building.

(2) An empirical formula is proposed to calculate the fundamental time period of

stepped building, as a function of regularity index.

Saptadip Sarkar (2010) studies the Design of Earthquake resistant multi stories RCC

building on a sloping ground which involves the analysis of simple 2-D frames of

varying floor heights and varying no of bays using a very popular software tool STAAD

Pro. Using the analysis results various graphs were drawn between the maximum axial

force, maximum shear force, maximum bending moment, maximum tensile force and

maximum compressive stress being developed for the frames on plane ground and

sloping ground. The graphs used to drawn comparison between the two cases and the

detailed study of ―Short Column Effect‖ failure was carried up. In addition to that the

detailed study of seismology was undertaken and the feasibility of the software tool to

be used was also checked.

Page | 38

Rajeeva and Tesfamariam (2012) Fragility based seismic vulnerability of structures

with consideration of soft -story (SS) and quality of construction (CQ) was

demonstrated on three, five, and nine story RC building frames designed prior to 1970s.

Probabilistic seismic demand model (PSDM) for those gravity load designed structures

was developed, using non-linear finite element analysis, considering the interactions

between SS and CQ. The response surface method is used to develop a predictive

equation for PSDM parameters as a function of SS and CQ. Result of the analysis shows

the sensitivity of the model parameter to the interaction of SS and CQ.

Mr. Ankur Agrawal (2012) presented a thesis paper entitled ―Seismic evaluation of

institute building” of NIT Rourkela. This project is similar to our project. The objective

was to evaluate the existing building for earthquake performance. Firstly preliminary

evaluation was done and then detailed evaluation was carried out. For applying

earthquake loads, equivalent static lateral force method was used according to IS

1893(Part 1):2002. The Demand Capacity Ratio (DCR) was carried out for beams and

columns in order to evaluate the member for seismic loads. Since the reinforcement

details of the building were not available as it was more than 50 years old, Design-1

was prepared applying only DEAD and LIVE loads according to IS 456:2000. That

helps in estimating the reinforcement present in the building and in assuming that that

much reinforcement is present. In Design-2 seismic loads were applied and from that

demand obtained from design-2 and capacity from design -1, the DCR was calculated.

STAAD-Pro V8i was used for loading and designing the building.

Page | 39

A paper on Prediction of potential damage due to severe earthquakes by Yucemen,

M.S., Ozcebe, G., and Pay, A.C (Department of Civil Engineering, Middle East

Technical University, Ankara 06531, Turkey and Department of Civil Engineering,

Purdue University). Here a statistical model is developed to estimate the seismic

vulnerability of low- to mid-rise reinforced concrete buildings. The model is based on

a novel utilization of the discriminant analysis technique of multivariate statistics.

A thesis on A New Methodology for Seismic Vulnerability Assessment of Existing

Buildings in Turkey by PAY, Ali Cihan, M.S.Thesis Supervisor: Prof. Dr. Güney

ÖZCEBE. In this study, a new methodology is presented to predict the seismic

vulnerability of reinforced concrete structures by statistical analysis based on a number

of structural parameters selected on the basis of engineering judgment and observations.

The available data collected after the 17 August and 12 November 1999 earthquakes in

Bolu, Düzce, and Kaynasli are examined by utilizing “discriminant analysis”.

A thesis on Seismic Retrofit Of Brick In filled R/C Frames With Lap Splice Problem

In Columns By AKGUZEL, Umut M.S. Thesis, Supervisor: Prof. Dr. Turan Ö TURAN.

Recent earthquakes revealed that many existing structures located in seismically active

regions of Turkey have inadequate lateral strength, stiffness or ductility. Lately, a

significant amount of research has been devoted to the study of various strengthening

techniques to enhance the seismic performance of the predominant structural system of

the region, which is reinforced concrete frames with unreinforced masonry infill. In this

context, an alternative strengthening method consists of externally applied carbon fiber

reinforced polymers (CFRP) over the brick in filled reinforced concrete frames has been

proposed and investigated.

Page | 40

Another article, subtitled “Keeping Preservation in the Forefront”, was posted on the

Old House Blog. It describes the unique problems faced when seismically retrofitting

an old home. The case studies concern older homes in Northern California. The authors

are David W. Look, AIA, Terry Wong, PE, and Sylvia Rose Augustus.

CHAPTER 3

METHODOLOGY

Page | 41

3.1: General

The purpose of this project is to assess the seismic vulnerability of an existing RC

structure and to provide for retrofit in case the members fail. The building under study

is an existing multi-storied residential building in Bangladesh. For applying earthquake

loads, Equivalent Static Force Method is used according to BNBC 1993. Reinforcement

details of our considered building were not available. For the purpose of study, in the

first step an analysis is done applying only Dead and Live Loads according to BNBC

Page | 42

1993. The building is then designed for Dead Load and Live Load only without the

consideration of seismic or wind load. In the second step, the building is analyzed for

seismic loading in addition to Dead Load and Live Load with proper load factor. Three

dimensional analyses is done using design software STAAD-Pro. The Demand

Capacity Ratio (DCR) is carried out for beams and columns in order to evaluate the

member for seismic loads. DCR is the ratio between the Demand and Capacity where

Demand is the amount of force or deformation imposed on an element or component

and Capacity is the permissible strength or deformation of a structural member or

system. From the Demand obtained from step-2 and Capacity from step-1, DCR is

calculated. If Demand is more than Capacity, the member is considered failed and vice

versa. Then retrofitting is carried out for the failed beams and columns. Steel Plating

Retrofitting Method is applied for the beams and Concrete Jacketing Retrofitting

Method is applied for the columns. The comparisons between Static and Dynamic

behavior are also shown in this paper.

The methodology of this study can be shown by the following flow chart-

Page | 43

3.2: Seismic Evaluation

Seismic Evaluation is a major tool in earthquake engineering which is used to

understand the response of buildings due to seismic excitations in a simpler manner.

In the past the buildings were designed just for gravity loads and seismic analysis is a

recent development. It is a part of structural analysis and a part of structural design

where earthquake is prevalent.

Seismic evaluation methods:

1. Preliminary Investigation

2. Detailed Evaluation

Designing the structure considering only Dead Load and Live Load

Modeling the structure using STAAD Pro and applying Seismic Load

Computing the DCR (Demand to Capacity Ratio)

Providing retrofit for the failed membes-Steel plating for beams and Concrete

jacketing for columns

Showing the comparision between Static and Dynamic behavior for the structure

Page | 44

Preliminary Investigation

The preliminary evaluation is a quick procedure to establish actual structural layout

and assess its characteristics that can affect its seismic vulnerability. It is an

approximate method based on conservative parameters to identify the potential

earthquake risk of a building and can be used for screening of buildings for detailed

evaluation. It also helps the design engineers to get acquainted with the building, its

potential deficiencies and behavior. A site visit is done as a part of preliminary

investigation in order to familiarize with the building and take note of the ground

conditions which are not reported in the drawings.

Detailed Evaluation

There are different types of detailed earthquake analysis methods. Some of them used

in the project are-

I. Equivalent Static Analysis

II. Response Spectrum Analysis

III. Time History Analysis

Equivalent Static Analysis

The Equivalent Static Analysis procedure is essentially an elastic design technique. It

is, however, simple to apply than the multi-model response method, with the absolute

simplifying assumptions being arguably more consistent with other assumptions

absolute elsewhere in the design procedure.

Page | 45

The Equivalent Static Analysis procedure consists of the following steps:

1. Estimate the first mode response period of the building from the design

response spectra.

2. Use the specific design response spectra to determine that the lateral base

shear of the complete building is consistent with the level of post-elastic

(ductility) response assumed.

3. Distribute the base shear between the various lumped mass levels usually

based on an inverted triangular shear distribution of 90% of the base shear

commonly, with 10% of the base shear being imposed at the top level to allow

for higher mode effects.

Response Spectrum Analysis

This approach permits the multiple modes of response of a building to be taken into

account. This is required in many building codes for all except for very simple or very

complex structures. The structural response can be defined as a combination of many

modes. Computer analysis can be used to determine these modes for a structure. For

each mode, a response is obtained from the design spectrum, corresponding to the

modal frequency and the modal mass, and then they are combined to estimate the

total response of the structure. In this the magnitude of forces in all directions is

calculated and then effects on the building are observed.

Following are the types of combination methods:

Page | 46

Absolute - peak values are added together

Square root of the sum of the squares (SRSS)

Complete quadratic combination (CQC) - a method that is an improvement on

SRSS for closely spaced modes

The result of a RSM analysis from the response spectrum of a ground motion is

typically different from that which would be calculated directly from a linear dynamic

analysis using that ground motion directly, because information of the phase is lost in

the process of generating the response spectrum.

In cases of structures with large irregularity, too tall or of significance to a community

in disaster response, the response spectrum approach is no longer appropriate, and

more complex analysis is often required, such as non-linear static or dynamic analysis.

Time History Analysis

Time History Analysis techniques involve the stepwise solution in the time domain of

the multi degree-of-freedom equations of motion which represent the actual

response of a building. It is the most sophisticated analysis method available to a

structural engineer. Its solution is a direct function of the earthquake ground motion

selected as an input parameter for a specific building. This analysis technique is usually

limited to checking the suitability of assumptions made during the design of important

structures rather than a method of assigning lateral forces themselves.

Page | 47

The steps involved in Time History Analysis are as follows:

1. Calculation of Modal matrix

2. Calculation of effective force vector

3. Obtaining of Displacement response in normal coordinate

4. Obtaining of Displacement response in physical coordinate

5. Calculation of effective earthquake response forces at each story

6. Calculation of maximum response

3.3: Seismic Retrofitting

Seismic Retrofitting is a modification of the structural and nonstructural components in

a building that aims to improve a building’s performance in future earthquakes.

Seismic strengthening or retrofitting is generally carried out in the following ways.

Structure Level or Global Retrofit Methods

Member Level or Local Retrofit Methods

Structure Level or Global Retrofit Methods

In structure level or global retrofit methods two approaches are used for structure level

retrofitting.

i) Conventional methods based on increasing the seismic resistance of existing

structure.

ii) Nonconventional methods based on reduction of seismic demands.

Page | 48

Conventional methods of retrofitting or strengthening are used to enhance the seismic

resistance of existing structures by eliminating or reducing the adverse effects of design

or construction. The methods include the options like adding of shear wall, infill walls

or steel braces.

In case of non-conventional methods, seismic base isolation and addition of

supplemented device techniques are the most popular. These techniques proceed with

quite different philosophy in the sense that it is fundamentally conceived to reduce the

horizontal seismic forces.

Member Level or Local Retrofit Methods

The member level retrofit or local retrofit of strengthening approach is to upgrade the

strength of the members, which are seismically deficient. This approach is more cost

effective as compared to the structure level retrofit. The most common method of

enhancing the individual member strength is jacketing. It includes the addition of

concrete, steel or fiber reinforced polymer (FRP) jackets for use in confining reinforced

concrete columns, beams, joints and foundations.

3.3.1: Steel Plating

In the present study, a series of experiments were conducted attempting to retrofit deep

reinforced concrete coupling beams using a bolted steel plate. In addition to the control

specimen, the other specimens were bolted with a steel plate on the side face to improve

the shear strength and inelastic behavior. A mechanical device was added to two

specimens to restrain plate buckling. Moreover, the plate buckling-restrained specimen

with a sufficient number of bolts in the anchor regions had a more stable response and

Page | 49

better inelastic performance under reversed cyclic loads. These findings can help

designers to a better understanding of this type of composite coupling beam.

In steel plating, steel plates are glued to beams to improve their flexural and shear

capacities. It increases the strength and stiffness of the beams and reduces the crack

width.

Advantages of Steel Plating:

Addition of steel plates is simple and can be rapidly applied

Does not reduce the story clear height significantly

Can be applied while the building is still in use

Relatively small increase in size of the existing section

3.3.2: Concrete Jacketing

Jacketing is the most popularly used method for strengthening of building columns. The

most common types of jackets are steel jacket, reinforced concrete jacket, fiber

reinforced polymer composite jacket, jacket with high tension materials like carbon

fiber, glass fiber etc.

Reinforced concrete jacketing can be employed as are pair or strengthening scheme.

Damaged regions of the existing members should be repaired prior to their jacketing.

There are two main purposes of jacketing of columns:

i) Increase in the shear capacity of columns in order to accomplish a strong

column-weak beam design and

Page | 50

ii) To improve the column's flexural strength by the longitudinal steel of the

jacket made continuous through the slab system are anchored with the

foundation.

Details for Reinforced Concrete Jacketing

Properties of Jackets:

Match with the concrete of the existing structure.

Compressive strength greater than that of the existing structures by

5 N/mm2 or at least equal to that of the existing structure.

Minimum Width of Jacket:

10 cm for concrete cast-in-place and 4 cm for shot Crete.

If possible, four-sided jacket should be used.

A monolithic behavior of the composite column should be assured.

Narrow gap should be provided to prevent any possible increase in

flexural capacity.

Minimum Area of Longitudinal Reinforcement:

3Afy, where, A is the area of contact in cm2 and fy is in kg/cm2.

Spacing should not exceed six times of the width of the new elements

(the jacket in the case) up to the limit of 60 cm.

Percentage of steel in the jacket with respect to the jacket area should be

limited between 0.015and 0.04.

At least, 12 mm bar should be used at every corner for a four sided

jacket.

Minimum Area of Transverse Reinforcement:

Page | 51

Designed and spaced as per earthquake design practice.

Minimum bar diameter used for ties is not less than 10 mm or 1/3 of the

diameter of the biggest longitudinal bar.

The ties should have 135-degree hooks with 10bar diameter anchorage.

Due to the difficulty of manufacturing 135-degree hooks on the field,

ties made up of multiple pieces, can be used.

Connectors:

Connectors should be anchored in both the concrete such that it may

develop at least80% of their yielding stress.

Distributed uniformly around the interface, avoiding concentration in

specific locations.

It is better to use reinforced bars (rebar) anchored with epoxy resins of

grouts.

Page | 52

Figure 3.3.1: Jacketing of RC Columns.

Limitations:

There are some disadvantages associated with the column jacketing techniques. They

are as follows:

In some cases the presence of beams may require majority of new longitudinal

bars to be bundled into the corners of the jacket;

With the presence of the existing column it is difficult to provide cross ties for

new longitudinal bars which are not at the corners of the jackets;

Jacketing is based mostly on engineering judgment as there is a dearth of

guidelines.

Page | 53

CHAPTER 4

BUILDING GEOMETRY AND

MANUAL STRUCTURAL ANALYSIS

Page | 54

4.1: General

A 9 story residential building is considered in this research study. The building has two

units. For simplification of work one unit is taken here. In Figure 4.1.1 the Layout of

Plan is shown and in Figure 4.1.2 the Layout of Plan with Grid Line is shown. Beam

size is same at all story. But there is difference in column sizes. In total six types of

column sizes are used in the building. The Column Dimensions are shown in the

following Table 4.1.

Table 4.1: Column Dimensions

Location Level 01 to 05 Level 06 to 09

Interior 23”*23” 15”*15”

Exterior 20”*20” 13”*13”

Page | 55

Corner 17”*17” 11”*11”

Dimension of beam: 12”*22” and 12”*18”.

Page | 56

Figure 4.1.1: Layout of Plan.

Page | 57

Figure 4.1.2: Layout of Plan with Grid Line.

Dimension of beam: 12”*22” and 12”*18”.

Dimension of column: Exterior column- 20”*20”, Interior column- 23”*23”, Corner column- 17”*17” for G to 4th floor and

Exterior column- 13”*13”, Interior column- 15”*15”, Corner column- 11”*11” for 5th to 8th floor.

Page | 58

4.2: Load Analysis and Design without Seismic Load

4.2.1: Design of Slab

Slab AB34 is taken for showing the detailed calculation. After calculating Dead Load

and Live Load for slab AB34 total load is found 0.271 ksf. In Table 4.2.1 total load for

all slabs are calculated. Then using ACI moment coefficient method, moment of slab

AB34 is calculated. In Table 4.2.2 moment calculation for all slabs are shown.

Given,

fc’ = 3 ksi, fy= 50 ksi

Live Load = 40 psf (BNBC 93, Table 6.2.3)

Floor Finish = 30 psf

Partition Wall = 40 psf (BNBC 93, Table 6.2.2)

Brick Wall Load = 0.5 kip/ft

Slab ID = AB34

Thickness =Perimeter

180 =

2(20+25)

180*12 = 6 inch

Load Calculation:

Dead Load, DL = (6

12*150+30+40)*1.4 = 203 psf

Live Load, LL = (40*1.7) = 68 psf

Total Load, w = 271 psf

= 0.271 ksf

Page | 59

Table 4.2.1: Slab Load Calculation

m= 𝐴

𝐵 =

20

25 = 0.8 (Case 4)

+MA(Pos) = CA DLWDL A2 + CA LLWLL A2

= (0.039*203

1000 *202) + (0.048 *

68

1000 *202)

= 4.4724 k-ft/ft

+MB(Pos) = CB DLWDL B2 + CB LLWLL B2

= (0.016*203

1000 *252) + (0.020 *

68

1000 *252)

= 2.88 k-ft/ft

Similarly,

- MA(Neg) = -0.071*271

1000 *202 = -7.6964 k-ft/ft

- MB(Neg) = -0.029*271

1000 *252 = -4.912 k-ft/ft

No

Slab

ID

La

(short)

ft

Lb

(long)

ft

m

t

(eqv.)

ft

Wself

k/ft2

FF

(eqv.)

k/ft2

DL

(ult)

k/ft2

LL

k/ft2

LL

(ult)

k/ft2

Wu

(total)

k/ft2

1 12AB 20.00 25.00 0.80 0.50 0.075 0.07 0.203 0.04 0.068 0.271

2 BC12 15.00 20.00 0.75 0.50 0.075 0.07 0.203 0.04 0.068 0.271

3 DC12 15.00 20.00 0.75 0.50 0.075 0.07 0.203 0.04 0.068 0.271

4 23AB 10.00 25.00 0.40 0.50 0.075 0.07 0.203 0.04 0.068 0.271

5 23BC 10.00 15.00 0.67 0.50 0.075 0.07 0.203 0.04 0.068 0.271

6 23CD 10.00 15.00 0.67 0.50 0.075 0.07 0.203 0.04 0.068 0.271

7 34AB 20.00 25.00 0.80 0.50 0.075 0.07 0.203 0.04 0.068 0.271

8 BC34 15.00 20.00 0.75 0.50 0.075 0.07 0.203 0.04 0.068 0.271

9 CD34 15.00 20.00 0.75 0.50 0.075 0.07 0.203 0.04 0.068 0.271

Page | 60

Table 4.2.2: Moment Calculations of Slabs

No

Slab

I.D.

La

ft

Lb

ft

case

Ca

(neg)

Cb

(neg)

Ca

(pos)

DL

Cb

(pos)

DL

Ca

(pos)

LL

Cb

(pos)

LL

DL(ult)

k/ft2

LL(ult)

k/ft2

Ma

(neg)

k-ft/ft

Ma

(pos)

k-ft/ft

Mb

(neg)

k-ft/ft

Mb

(pos)

k-ft/ft

1 1,2,A,B 19 24 4 0.071 0.029 0.039 0.016 0.048 0.020 0.203 0.068 6.95 4.04 4.53 2.65

2 B,C,1,2 14 19 9 0.078 0.014 0.031 0.007 0.046 0.013 0.203 0.068 4.14 1.85 1.37 0.83

3 D,C,1,2 14 19 4 0.076 0.024 0.043 0.013 0.052 0.016 0.203 0.068 4.04 2.40 2.35 1.35

4 2,3,B,C 9 14 2 0.076 0.015 0.031 0.006 0.052 0.011 0.203 0.068 1.67 0.80 0.80 0.39

5 2,3,C,D 9 14 9 0.082 0.009 0.034 0.005 0.053 0.010 0.203 0.068 1.81 0.84 0.48 0.34

6 3,4,A,B 19 24 4 0.071 0.029 0.039 0.016 0.048 0.020 0.203 0.068 6.95 4.04 4.53 2.65

7 B,C,3,4 14 19 6 0.088 0.000 0.048 0.012 0.055 0.016 0.203 0.068 4.67 2.64 0.00 1.27

8 C,D,3,4 14 19 4 0.076 0.024 0.043 0.013 0.052 0.016 0.203 0.068 4.04 2.40 2.35 1.35

Page | 61

d- Check:

ρ = 0.85ß fc’

fy

Ɛu

Ɛu+Ɛt

= 0.85*0.85*3

50*

0.003

0.003+0.004

= 0.0186

Now, d = √Mmax

Øρfyb(1−0.59ρfy/fc’)

= √7.6964∗12

0.9∗0.0186∗50∗12∗(1−0.59∗0.0186∗50

3)

= 3.35 inch <dmin= (6-1) = 5 inch

So, OK

So, Thickness = 6 inch

4.2.2: Design of Beam

A detailed calculation for beam A3B3 is shown here as a sample calculation. For

beam A3B3 load on beam is calculated. Then in Table 4.2.3 load calculation for all

beams has been done. Finally by using ACI coefficient method beam size is

calculated.

Beam ID = A3B3

Slab Area = (5*25) + 1

2(5+25)*10

= 275 ft2

Page | 62

Slab Load, w = 0.271 ksf

So, Load on Slab = (0.271*275) k = 74.525 k

Let the size of the Beam is 12" * 22"

Beam Load = Load for self-weight + Wall load

= {(12∗22

144 *25*

150

1000 ) + (

5

12 *10*

120

1000∗ 25)}1.4

= 27.125 k

So, Load on Beam = Load from Slab + Beam load

= 74.525+27.125

= 101.65 k/25ft

= 4.1 k/ft

Page | 63

Table 4.2.3: Beam Load Calculation

Beam

ID

Slab-1 Slab-2 Wall Beam

wdlu

k/ft

wllu

k/ft

wtu

k/ft No.

Side

wdlu

k/ft

wllu

k/ft

No.

Side

wdlu

k/ft

wllu

k/ft

h

ft

w.wall

k/ft

b

ft

h

ft

w.beam

k/ft

A/1-2 10 0 0.00 0.00 1 S 0.74 0.25 10.00 0.56 1.00 1.83 0.38 1.68 0.25 1.93

B/1-2 1 S 0.74 0.25 2 L 1.31 0.44 10.00 0.56 1.00 1.83 0.38 2.99 0.69 3.67

C/1-2 2 L 1.31 0.44 3 L 1.16 0.39 10.00 0.56 1.00 1.83 0.38 3.41 0.83 4.24

D/1-2 3 L 1.16 0.39 10 0 0.00 0.00 10.00 0.56 1.00 1.83 0.38 2.10 0.39 2.49

A/2-3 10 0 0.00 0.00 4 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 0.94 0.00 0.94

B/2-3 4 S 0.00 0.00 5 S 0.25 0.08 10.00 0.56 1.00 1.83 0.38 1.19 0.08 1.28

C/2-3 5 S 0.25 0.08 6 S 0.14 0.05 10.00 0.56 1.00 1.83 0.38 1.33 0.13 1.46

D/2-3 6 S 0.14 0.05 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 1.08 0.05 1.13

A/3-4 10 L 0.00 0.00 2 S 0.28 0.10 10.00 0.56 1.00 1.83 0.38 1.23 0.10 1.32

B/3-4 7 S 0.74 0.25 8 S 0.24 0.08 10.00 0.56 1.00 1.83 0.38 1.92 0.33 2.25

C/3-4 1 L 1.44 0.48 2 S 0.28 0.10 10.00 0.56 1.00 1.83 0.38 2.67 0.58 3.25

D/3-4 9 L 1.16 0.39 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 2.10 0.39 2.49

1/A-B 1 L 1.44 0.48 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 2.39 0.48 2.87

1/B-C 2 S 0.28 0.10 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 1.23 0.10 1.32

1/C-D 3 S 0.49 0.16 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 1.43 0.16 1.59

2/A-B 1 L 1.44 0.48 4 L 1.02 0.34 10.00 0.56 1.00 1.83 0.38 3.40 0.82 4.22

2/B-C 2 S 0.28 0.10 5 L 0.85 0.28 10.00 0.56 1.00 1.83 0.38 2.08 0.38 2.46

2/C-D 3 S 0.49 0.16 6 L 0.92 0.31 10.00 0.56 1.00 1.83 0.38 2.36 0.47 2.83

3/A-B 4 L 1.02 0.34 7 L 1.44 0.48 10.00 0.56 1.00 1.83 0.38 3.40 0.82 4.22

3/B-C 5 L 0.85 0.28 8 S 0.24 0.08 10.00 0.56 1.00 1.83 0.38 2.04 0.37 2.40

3/C-D 6 L 0.92 0.31 9 S 0.49 0.16 10.00 0.56 1.00 1.83 0.38 2.36 0.47 2.83

4/A-B 7 L 1.44 0.48 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 2.39 0.48 2.87

4/B-C 8 S 0.24 0.08 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 1.19 0.08 1.27

4/C-D 9 S 0.49 0.16 10 S 0.00 0.00 10.00 0.56 1.00 1.83 0.38 1.43 0.16 1.59

Page | 64

Now,

+M = 1

14wL2 =

1

14*3.4*252 = 151.79 k-ft

-M = 1

10wL2 =

1

10*3.4*252 = 212.5 k-ft

ρ = 0.85Øfc’

fy

Ɛu

Ɛu+Ɛt

= 0.85*0.85*3

50*

0.003

0.003+0.004

= 0.0186

d = √Mmax

Øρfyb(1−0.59ρfy/fc’)

=√212.5∗12

0.9∗0.0186∗50∗12∗(1−0.59∗0.0186∗50

3)

= 17.62 inch

= (17.62+2.5) inch

= 20.13 inch < 22inch

So, OK

So, Beam size = 12" * 22"

Page | 65

4.2.3: Design of Column

In Table 4.2.4 column load calculations is shown. Manually the column load of B3 is

shown here. After calculating the load a column size is assumed and the total load is

found by including the self-weight. Then the gross area of column is calculated and

suitable column size is selected.

Column Name = B3

Load Calculation on Column from Roof Slab:

Thickness of Slab = 6 inch;

Live Load = 30psf

Lime Concrete = 30psf;

Dead Load, DL= (6

12*150+30)*1.4 = 147 psf

Live Load, LL = (30*1.7) = 51 psf

Total Load on Slab, w = 198 psf

= 0.198 ksf

= 0.2 ksf

Beam A3B3:

Slab Load = {(25*5)+1

2(5+25)10}*0.2 = 55k

Beam Load = (12∗22

144 *25*

150

1000 ) 1.4 = 9.625k

So Load on Beam = 55+9.625

25 = 2.585 k/ft

Page | 66

Beam B2B3:

Slab Load = {(10*12.5)+1

2*10*5}*0.2 = 30k

Beam Load = (12∗22

144 *10*

150

1000 ) 1.4 = 3.85k

So Load on Beam = 30+3.85

10 = 3.385 k/ft

Beam B3B4:

Slab Load = {(1

2 *20*10)+

1

2(20+5)7.5}*0.2 = 38.75k

Beam Load = (12∗22

144 *20*

150

1000 ) 1.4 = 7.68k

So Load on Beam = 38.75+7.68

20 = 2.32 k/ft

Beam B3C3:

Slab Load = {(1

2 *15*7.5)+

1

2(5+15)5}*0.2 = 21.25k

Beam Load = (12∗22

144 *15*

150

1000 ) 1.4 = 5.775k

So Load on Beam = 21.25+5.775

15 = 1.80 k/ft

Now,

Load on Column = 2.585*25

2 +3.385*

10

2 +2.32*

20

2 +1.80*

15

2

= 85.85 k

Page | 67

Load Calculation on Column from Floor Slab:

Total Load on Slab, w = 0.271 ksf

Beam A3B3:

Slab Load = {(25*5)+1

2(5+25)10}*0.271 = 74.525k

Beam Load = (12∗22

144 *25*

150

1000 ) 1.4 = 9.625k

So Load on Beam = 74.525+9.625

25 = 3.366 k/ft

Beam B2B3:

Slab Load = {(10*12.5)+1

2*10*5}*0.271 = 40.65k

Beam Load = (12∗22

144 *10*

150

1000 ) 1.4 = 3.85k

So Load on Beam = 40.65+3.85

10 = 4.45 k/ft

Beam B3B4:

Slab Load = {(1

2 *20*10)+

1

2(20+5)7.5}*0.271 = 52.51k

Beam Load = (12∗22

144 *20*

150

1000 ) 1.4 = 7.68k

So Load on Beam = 52.51+7.68

20 = 3 k/ft

Beam B3C3:

Slab Load = {(1

2 *15*7.5)+

1

2(5+15)5}*0.271 = 28.79k

Beam Load = (12∗22

144 *15*

150

1000 ) 1.4 = 5.775k

Page | 68

So Load on Beam = 28.79+5.775

15 = 2.30 k/ft

Now,

Load on Column = 3.366*25

2 +4.45*

10

2 +3*

20

2 +2.30*

15

2

= 111.575 k

Assuming Column size 12" * 12" from 5th to 8th Floor

Self-Weight of Column = 12∗12

144 *10*

150

1000

= 1.5 k

8th Floor = 85.85 k

7th Floor = 85.85+111.575+1.5 = 198.925

6th Floor = 85.85+(111.575*2)+(1.5*2) = 312.00 k

5th Floor = 85.85+(111.575*3)+(1.5*3) = 425.075 k

Assuming Column size 15" * 15" from GF to 4th Floor

Self-Weight of Column = 15∗15

144 *10*

150

1000

= 2.34 k

Page | 69

4th Floor = 85.85+(111.575*4)+(1.5*3)+2.34 = 538.99 k

3rd Floor = 85.85+(111.575*5)+(1.5*3)+(2.34*2) = 652.905 k

2nd Floor = 85.85+(111.575*6)+(1.5*3)+(2.34*3) = 766.82 k

1st Floor = 85.85+(111.575*7)+(1.5*3)+(2.34*4) = 880.735 k

GF = 85.85+(111.575*8)+(1.5*3)+(2.34*5) = 994.65 k

In Table 4.2.4 axial load for each floor of B3 column has been shown. For manual

calculation it is found that at GF column load is 994.65 kip and from Table 4.2.4 the

load is 977.24 kip at GF. So, it can be said that the design is approximately ok.

Page | 70

Table 4.2.4: Column Load Calculation

Level

Slab-1 Slab-2 Wall-1 Wall-2 Beam Column Accumulated

Load

kip

l1

ft

l2

ft

t

ft

w

kip

l1

ft

l2

ft

t

ft

w

kip

h

ft

l

ft

w

kip

h

ft

l

ft

w

kip

l

ft

w

kip

h

ft

w

kip

Fl. 9 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 2.65 101.07

Fl. 8 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 2.65 207.23

Fl. 7 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 2.65 313.40

Fl. 6 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 2.65 419.56

Fl. 5 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 6.49 531.10

Fl. 4 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 6.49 642.63

Fl. 3 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 6.49 754.17

Fl. 2 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 6.49 865.70

Fl. 1 20 15 0.7 31.5 0 0 0 0.00 10 20 10.00 10 15 7.50 35 9.61 10 6.49 977.24

Page | 71

From 5th to 8th Floor, Pu = 425.075 k

Pu = 0.8Ø[0.85 fc’ (Ag-Ast)+fyAst]

Or, 425.075 = 0.80*0.70*[0.85*3*(Ag-0.015Ag)+50*0.015Ag]

Or, 425.075 = 1.83Ag

Or, Ag = 232.28 in2

So, √232.28 = 15.24 inch

So, Column size = 15" * 15"

From GF to 4th Floor, Pu = 994.65 k

Or, 994.65 = 1.83Ag

Or, Ag = 543.52 in2

So, √543.52 = 23.31 inch

So, Column size = 23" * 23"

4.2.4: One Way Slab Design

There is a one way slab in this building. So, the load and moment for one way slab is

calculated separately.

Page | 72

Slab ID = AB23

Load Calculation:

Dead Load, DL = (6

12*150+30+40)*1.4 = 203 psf

Live Load, LL = (40*1.7) = 68 psf

Total Load, w = 271psf = 0.271 ksf

Moment Calculation:

+M(short) = wL2/8 = 0.271*102/8

= 3.39 k-ft/ft

4.3: Seismic Load Calculation

Static Equivalent Earthquake Method is used for seismic load calculation of the

considered building. This building is situated in Zone 2. In Table 4.3.1 and Table 4.3.2

seismic load calculation for each grid of different floors are shown.

We know, V= 𝑍𝐼𝐶

𝑅*w

Where:

Z= 0.15 (Dhaka Seismic Zone 2)

I = 1.0 (Standard Occupancy Structure, Residential Building)

R= 5

Page | 73

Now,

T= Ct (hn)3/4

= 0.049*(87

3.28)3/4

= 0.573

∴ C = 1.25S / T2/3

= (1.25*1.5) / (0.573)2/3

= 2.17

W = Dead load of Column for each Grid

Now, Ft = 0 as T < 0.7

In Table 4.3.1 Seismic Load Calculation for Each Grid are shown.

And then in Table 4.3.2: Total Seismic Load Calculation is presented.

Page | 74

Table 4.3.1: Seismic Load Calculation for Each Grid

Grid A

Floor A1 Colm A2 Colm A3 Colm A4 Colm Colm

Load(k)

Total

Wi(k)

Height,

Hi(ft)

Wihi(k-ft)

Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k)

Fl. 9 33.2 39.4547 43.64 43.64 43.64 43.64 33.2 33.2 153.68 159.9347 87 13914.3

Fl. 8 66.41 33.21 87.28 43.64 87.28 43.64 66.41 33.21 307.38 153.7 77 11834.9

Fl. 7 99.61 33.2 130.92 43.64 130.92 43.64 99.61 33.2 461.06 153.68 67 10296.6

Fl. 6 132.82 33.21 174.56 43.64 174.56 43.64 132.82 33.21 614.76 153.7 57 8760.9

Fl. 5 169.86 37.04 222.03 47.47 222.03 47.47 169.86 37.04 783.78 169.02 47 7943.94

Fl. 4 206.9 37.04 269.51 47.48 269.51 47.48 206.9 37.04 952.82 169.04 37 6254.48

Fl. 3 243.94 37.04 316.99 47.48 316.99 47.48 243.94 37.04 1121.86 169.04 27 4564.08

Fl. 2 280.98 37.04 364.46 47.47 364.46 47.47 280.98 37.04 1290.88 169.02 17 2873.34

Fl. 1 318.02 37.04 411.94 47.48 411.94 47.48 318.02 37.04 1459.92 169.04 7 1183.28

SUM 67625.8

Page | 75

Grid B

Floor B1 Colm B2 Colm B3 Colm B4 Colm Colm

Load(k)

Total

Wi(k)

Height,

Hi(ft)

Wihi(k-ft)

Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k)

Fl. 9 46.89 46.89 61.26 61.26 61.261 61.261 46.89 46.89 216.30095 216.30095 87 18818.2

Fl. 8 93.78 46.89 122.52 61.26 122.522 61.2609 93.78 46.89 432.6018 216.30085 77 16655.2

Fl. 7 140.67 46.89 183.783 61.2627 183.783 61.2609 140.67 46.89 648.9053 216.3035 67 14492.3

Fl. 6 187.55 46.88 245.044 61.2609 245.044 61.2609 187.55 46.88 865.187 216.2817 57 12328.1

Fl. 5 238.28 50.73 310.141 65.0971 310.141 65.0971 238.28 50.73 1096.8412 231.6542 47 10887.7

Fl. 4 289 50.72 375.238 65.0971 375.238 65.0971 289 50.72 1328.4754 231.6342 37 8570.47

Fl. 3 339.73 50.73 440.335 65.0971 440.335 65.0971 339.73 50.73 1560.1296 231.6542 27 6254.66

Fl. 2 390.45 50.72 505.432 65.0971 505.432 65.0971 390.45 50.72 1791.7638 231.6342 17 3937.78

Fl. 1 441.18 50.73 570.529 65.0971 570.529 65.0971 441.18 50.73 2023.418 231.6542 7 1621.58

SUM 93566

Page | 76

Grid C

Floor C1 Colm C2 Colm C3 Colm C4 Colm Colm

Load(k)

Total

Wi(k)

Height,

Hi(ft)

Wihi(k-ft)

Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k)

Fl. 9 37.77 37.77 49.51 49.51 49.51 49.51 37.77 37.77 174.56 174.56 87 15186.7

Fl. 8 75.53 37.76 99.03 49.52 99.03 49.52 75.53 37.76 349.12 174.56 77 13441.1

Fl. 7 113.3 37.77 148.54 49.51 148.54 49.51 113.3 37.77 523.68 174.56 67 11695.5

Fl. 6 151.06 37.76 198.05 49.51 198.05 49.51 151.06 37.76 698.22 174.54 57 9948.78

Fl. 5 192.67 41.61 251.4 53.35 251.4 53.35 192.67 41.61 888.14 189.92 47 8926.24

Fl. 4 234.27 41.6 304.75 53.35 304.75 53.35 234.27 41.6 1078.04 189.9 37 7026.3

Fl. 3 275.87 41.6 358.1 53.35 358.1 53.35 275.87 41.6 1267.94 189.9 27 5127.3

Fl. 2 317.47 41.6 411.45 53.35 411.45 53.35 317.47 41.6 1457.84 189.9 17 3228.3

Fl. 1 359.07 41.6 464.8 53.35 464.8 53.35 359.07 41.6 1647.74 189.9 7 1329.3

SUM 75909.6

Page | 77

Grid D

Floor D1 Colm D2 Colm D3 Colm D4 Colm Colm

Load(k)

Total

Wi(k)

Height,

Hi(ft)

Wihi(k-ft)

Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k) Load(k) Wi(k)

Fl. 9 24.08 24.08 31.89 31.89 31.89 31.89 24.08 24.08 111.94 111.94 87 9738.78

Fl. 8 48.16 24.08 63.78 31.89 63.78 31.89 48.16 24.08 223.88 111.94 77 8619.38

Fl. 7 72.25 24.09 95.68 31.9 95.68 31.9 72.25 24.09 335.86 111.98 67 7502.66

Fl. 6 96.33 24.08 127.57 31.89 127.57 31.89 96.33 24.08 447.8 111.94 57 6380.58

Fl. 5 124.25 27.92 163.3 35.73 163.3 35.73 124.25 27.92 575.1 127.3 47 5983.1

Fl. 4 152.17 27.92 199.09 35.79 199.09 35.79 152.17 27.92 702.52 127.42 37 4714.54

Fl. 3 180.01 27.84 234.75 35.66 234.75 35.66 180.01 27.84 829.52 127 27 3429

Fl. 2 208 27.99 270.48 35.73 270.48 35.73 208 27.99 956.96 127.44 17 2166.48

Fl. 1 235.92 27.92 306.21 35.73 306.21 35.73 235.92 27.92 1084.26 127.3 7 891.1

SUM 49425.6

Page | 78

Table 4.3.2: Total Seismic Load Calculation

Floor

Hx(ft)

Fx (kip)

Grid A Grid B Grid C Grid D Total

8th 87 18.792 26.4915 21.4542 13.9026 161.281

7th 77 16.632 23.4465 18.9882 12.3046 142.743

6th 67 14.472 20.4015 16.5222 10.7066 124.205

5th 57 12.312 17.3565 14.0562 9.1086 105.667

4th 47 11.1625 15.322 12.6101 8.5399 95.269

3rd 37 8.7875 12.062 9.9271 6.7229 74.999

2nd 27 6.4125 8.802 7.2441 4.9059 54.729

1st 17 4.0375 5.542 4.5611 3.0889 34.459

GF 7 1.6625 2.282 1.8781 1.2719 14.189

Grid A:

W = A1 + A2 + A3 +A4

= 318.02+411.94+411.94+318.02

= 1459.92 kip

V = 𝑍𝐼𝐶

𝑅*w

= 0.15∗1.0∗2.17

5 * 1459.92

= 95.04 kip

Fx = (𝑉−𝐹𝑡)𝑊𝑥ℎ𝑥

⅀𝑊𝑖ℎ𝑖

For GF to 4th floor, Fx = (95.04 −0)∗169.04∗ℎx

67625.8 = 0.238hx

For 5th to 8th floor, Fx = (95.04 −0)∗153.7∗ℎx

67625.8 = 0.216hx

Page | 79

Grid B:

W = B1 + B2 + B3 +B4

= 441.18+570.53+570.53+441.18

= 2023.42 kip

V = 𝑍𝐼𝐶

𝑅*w

= 0.15∗1.0∗2.17

5 * 2023.42

= 131.72 kip

Fx = (𝑉−𝐹𝑡)𝑊𝑥ℎ𝑥

⅀𝑊𝑖ℎ𝑖

For GF to 4th floor, Fx = (131.72−0)∗231.6542∗ℎx

93565.98 = 0.326hx

For 5th to 8th floor, Fx = (131.72−0)∗216.3035∗ℎx

93565.98 = 0.305hx

Grid C:

W = C1 + C2 + C3 +C4

= 359.07+464.80+464.80+359.07

= 1647.74 kip

V = 𝑍𝐼𝐶

𝑅*w

= 0.15∗1.0∗2.17

5 * 1647.74

Page | 80

= 107.27 kip

Fx = (𝑉−𝐹𝑡)𝑊𝑥ℎ𝑥

⅀𝑊𝑖ℎ𝑖

For GF to 4th floor, Fx = (107.27 −0)∗189.9∗ℎx

75909.58 = 0.268hx

For 5th to 8th floor, Fx = (107.27 −0)∗174.54∗ℎx

75909.58 = 0.247hx

Grid D:

W = D1 + D2 + D3 +D4

= 235.92+306.21+306.21+235.92

= 1084.26 kip

V = 𝑍𝐼𝐶

𝑅*w

= 0.15∗1.0∗2.17

5 * 1084.26

= 70.59 kip

Fx = (𝑉−𝐹𝑡)𝑊𝑥ℎ𝑥

⅀𝑊𝑖ℎ𝑖

For GF to 4th floor, Fx = (70.59 −0)∗111.94∗ℎx

49425.62 = 0.1598hx

For 5th to 8th floor, Fx = (70.59 −0)∗127.3∗ℎx

49425.62 = 0.182hx

So, Total Load = (Load from Grid A + Grid B + Grid C + Grid D)*2

Page | 81

CHAPTER 5

3D STRUCTURAL SOFTWARE

ANALYSIS AND RETROFITTING

Page | 82

5.1: General

The design philosophy adopted in the code is to ensure that structure possess minimum

strength to resist minor earthquake, moderate earthquake and major earthquake. Actual

forces on structures during earthquake are much higher than the design forces specified

in the code.

A 9 story RC structure is considered here. The building is mainly a residential

apartment. Since the reinforcement details were not available a design is prepared in

the first step to estimate the reinforcement of the building considering Dead Load and

Live Load only. For concrete design ACI code is followed. In the second step, another

design is prepared in which seismic loads are also applied following Equivalent Static

Force Method. Designing software STAAD Pro is used for designing purpose with full

confidence on it. Supports are fixed. Then checks for beams and columns are done

according to DCR (Demand to Capacity Ratio) concept. Then retrofitting is carried out

for the failed members. Steel Plating Retrofitting Method is applied for beams and

Concrete Jacketing Retrofitting Method for columns. The comparisons between Static

and Dynamic behavior are also shown.

Page | 83

5.2: Geometric Model and Design Parameters

Figure 5.2.1: Plan of Building.

Figure 5.2.2: Side View of Building.

Page | 84

Figure 5.2.3: Whole Building with Member Properties Applied To All the Members

(3-D View).

Member:

There are 450 beams in our structure.

Beams:

Dimension of beam in our structure is 12”*22” and 12”*18”.

Columns:

There are 288 columns in our structure.

Page | 85

Table 5.2.1: Column Dimensions

Dimension

Exterior Interior Corner

G to 4th 20"*20" 23"*23" 17"*17"

5th to 8th 13"*13" 15"*15" 11"*11"

Design Parameters:

Building type: Reinforced concrete frame.

Usage: Residential apartment.

BNBC’93 code is followed.

Grade of concrete, fc=3 ksi.

Type of steel used- Mild Steel implies, fy=50 ksi.

Live load= 30 psf at roof (accessible)

40 psf at all other floors (BNBC’93; Table 6.2.3).

Cover provided = 2.5” for beams.

Cover provided = 2” for columns.

Brick load=0.5 k/ft.

Floor load= 30 psf ( BNBC’93).

Location: Dhaka.

Plan dimension: 120’*50’

Building height: 90 ft.

Page | 86

5.3: Loads

Members are loaded with dead and live load as per BNBC’93 load combinations is

applied.

Load Combinations:

DL

LL

1.4 * DL+ 1.7 * LL

0.75(1.4DL+1.7LL+1.87EQ)

1.4(DL+LL+EQ)

Dead Load:

Includes self-weight of all members + Brick Load + Floor load from slabs

Brick load due to 10 ft high brick wall and 5 inch thick and of 120 lb/ft3 density

= (5/12)*10*120=500 lb/ft udl.

Page | 87

Figure 5.3.1: Dead Load on Building.

Page | 88

Figure 5.3.2: Dead Load on First Floor (Load of Walls on Beam + Self-Wt.).

Figure 5.3.3: Dead Load on First Floor (Floor Finish + Self-Wt.).

Page | 89

Live Load:

30 psf at roof (accessible)

40 psf at all other floors (BNBC’93; Table 6.2.3)

Figure 5.3.4: Live Load on Building.

Page | 90

Figure 5.3.5: Live Load on first Floor.

5.4: Check for Beams

Steps:

The maximum moment induced on beam is obtained from Step- 2.

The capacity of members is calculated from the reinforcement obtained from

Step- 1.

Demand Capacity Ratio= Max. Moment/ Capacity.

If the value of DCR<1 then the members is considered PASS i.e. it can take the

moment induced by seismic loading.

If the value of DCR>1 then the member is considered Fail i.e. it can’t take the

load due to earthquake.

Page | 91

Sample Calculation of Level 01 Beam Check with Seismic:

Beam ID: A12

Beam No: 84 (According to STAAD Pro)

Moment capacity of beam,

M=ΦAsfy(d- 𝑎

2)

= 0.9*1.58*50*(19.5-2.5

2)

= 1297.58 k-inch

Maximum –ve moment: -1297.58 k-in or -108.13 k-ft (Capacity)

Maximum +ve moment: 1297.58 k-in or 108.13 k-ft (Capacity)

Figure 5.4.1: Concrete Design of Beam in STAAD Pro.

Page | 92

Maximum –ve moment: -143.99 k-ft (Demand)

Maximum +ve moment: 58.71 k-ft (Demand)

So, DCR= Demand / Capacity

For +ve moment DCR= 58.71/108.13 = 0.543(DCR<1) [Pass]

For -ve moment DCR= 143.99/108.13 = 1.33(DCR>1) [Fail]

Beam checks for all beams with seismic load and without seismic load are shown in the

following Table 5.4.1 and 5.4.2 respectively.

Page | 93

Table 5.4.1: Level 01 Beam Check with Seismic Loads

Beam

ID

Beam

No

Demand Capacity DCR Result

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

1AB 81 -118.78 72.35 -120.667 108.5 0.984 0.667 pass pass

1BC 82 -39.56 15.93 -120.667 108.5 0.328 0.147 pass pass

1CD 83 -46.12 19.37 -62.75 62.75 0.735 0.309 pass pass

A12 84 -143.99 58.71 -108.13 108.13 1.33 0.543 fail pass

B12 85 -143.99 68.77 -134.25 108.5 1.073 0.634 fail pass

C12 86 -143.99 67.86 -134.25 108.5 1.073 0.625 fail pass

D12 87 -143.99 58.71 -108.5 108.5 1.327 0.541 fail pass

2AB 88 -162.95 92.26 -192.25 134.25 0.848 0.687 pass pass

2BC 89 -54.19 23.7 -192.25 134.25 0.282 0.177 pass pass

2CD 90 -49.97 26.01 -84.0833 84.08333 0.594 0.309 pass pass

A23 91 -142.7 113.51 -108.5 108.5 1.315 1.046 fail fail

B23 92 -142.7 138.17 -134.25 108.5 1.063 1.273 fail fail

C23 93 -142.7 142.03 -134.25 108.5 1.063 1.309 fail fail

D23 94 -142.7 123.9 -108.5 108.5 1.315 1.142 fail fail

3AB 95 -163.01 92.27 -192.25 134.25 0.848 0.687 pass pass

3BC 96 -163.01 23.73 -192.25 134.25 0.848 0.177 pass pass

3CD 97 -45.73 26.46 -84.0833 84.08333 0.544 0.315 pass pass

A34 98 -143.14 56.46 -108.5 108.5 1.319 0.520 fail pass

B34 99 -143.14 65.91 -134.25 108.5 1.066 0.607 fail pass

C34 100 -143.14 66.62 -134.25 108.5 1.066 0.614 fail pass

D34 101 -147.45 60.55 -108.5 108.5 1.359 0.558 fail pass

4AB 102 -119.06 72.37 -120.667 108.5 0.987 0.667 pass pass

4BC 103 -40.07 15.56 -120.667 108.5 0.332 0.143 pass pass

4CD 104 -34.38 19.42 -62.75 62.75 0.548 0.309 pass pass

Page | 94

Table 5.4.2: Level 01 Beam Check without Seismic Loads

Beam

ID

Beam

No

Demand Capacity DCR Result

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

Max -Ve

Moment

(k-ft)

Max +Ve

Moment

(k-ft)

1AB 81 -119.91 73.66 -120.667 108.5 0.994 0.679 pass pass

1BC 82 -40.21 15.24 -120.667 108.5 0.333 0.140 pass pass

1CD 83 -34.52 21.19 -62.75 62.75 0.550 0.338 pass pass

A12 84 -68.33 44.24 -108.5 108.5 0.631 0.409 pass pass

B12 85 -99.42 62.11 -134.25 108.5 0.741 0.572 pass pass

C12 86 -96.83 59.92 -134.25 108.5 0.721 0.552 pass pass

D12 87 -68.33 44.24 -108.5 108.5 0.630 0.408 pass pass

2AB 88 -151.51 -159.2 -192.25 134.25 0.788 -1.186 pass pass

2BC 89 -54.62 23.26 -192.25 134.25 0.284 0.173 pass pass

2CD 90 -47.68 27.14 -84.0833 84.08333 0.567 0.323 pass pass

A23 91 -17.36 0.45 -108.5 108.5 0.160 0.004 pass pass

B23 92 -20.49 3.48 -134.25 108.5 0.153 0.032 pass pass

C23 93 -20.66 3.59 -134.25 108.5 0.154 0.033 pass pass

D23 94 -19.89 24.98 -108.5 108.5 0.183 0.230 pass pass

3AB 95 -159.25 93.28 -192.25 134.25 0.828 0.695 pass pass

3BC 96 -54.58 23.34 -192.25 134.25 0.284 0.174 pass pass

3CD 97 -48.75 27.98 -84.0833 84.08333 0.580 0.333 pass pass

A34 98 -68.23 44.23 -108.5 108.5 0.629 0.408 pass pass

B34 99 -99.58 62.11 -134.25 108.5 0.742 0.572 pass pass

C34 100 -97.02 59.88 -134.25 108.5 0.723 0.552 pass pass

D34 101 -65.63 41.86 -108.5 108.5 0.605 0.386 pass pass

4AB 102 -107.53 73.68 -120.667 108.5 0.891 0.679 pass pass

4BC 103 -40.68 15.5 -120.667 108.5 0.337 0.143 pass pass

4CD 104 -33.34 21.28 -62.75 62.75 0.531 0.339 pass pass

Page | 95

Figure 5.4.2: Beam of First Floor Eligible for Steel Plating.

5.5: Check for Columns

Steps:

The maximum axial load induced on beam is obtained from Step- 2.

The capacity of members is calculated from the reinforcement obtained from

Step- 1.

Demand capacity Ratio= Maximum load/ Axial capacity.

If the value of DCR<1 then the members is considered PASS i.e. it can take the

load induced by seismic loading.

If the value of DCR>1 then the member is considered Fail i.e. it can’t take the

load due to earthquake.

Page | 96

Sample Calculation of Level 01 Interior Column Check with Seismic:

Column ID: B3

Column No: 74 (According to STAAD Pro)

Table 5.5.1: Parameters for Column Check

Width, W(in) 23 C. cover, cc (in) 2

Height, H(in) 23 Total layer, NL 4

Agross, Ag(in²) 529 Steel area, As(in²) 14.72622

Bar dia, db(in) 1.25 Steel ratio, p(%) 2.784

Factor, ρh 0.7 Alpha = 0.8

Nominal Axial load capacity, Pn = As*fy + 0.85 fc’ * (Ag – As)

= 14.72622*50 + 0.85*3*(529-14.72622)

= 2047.71 kip

Ult. Axial Strength, Pult = 0.8*0.7*Pn= 0.8*0.7*2047.71= 1146.72 kip

Maximum Load: 1146.72 kip (Capacity)

Page | 97

Figure 5.5.1: Concrete Design of Column in STAAD Pro.

Maximum Load: 1260.51 kip (Demand)

So, DCR= Demand / Capacity

= 1260.51/1146.72

= 1.09923(DCR>1) [Fail]

Column checks for all levels are shown in the following Table 5.5.2. Check is done for

one exterior, one interior and one corner column for each level.

Page | 98

Table 5.5.2: Column Check

Exterior Column A2 Check

Level Demand(k) Capacity(k) DCR Result

9 78.46 335.25 0.23403 pass

8 166.597 335.25 0.49693 pass

7 254.348 335.25 0.75868 pass

6 341.79 335.25 1.01951 fail

5 432.084 821.64 0.52588 pass

4 522.532 821.64 0.63596 pass

3 612.921 821.64 0.74597 pass

2 703.343 821.64 0.85602 pass

1 793.79 821.64 0.96611 pass

Page | 99

Interior Column B3 Check

Level Demand(k) Capacity(k) DCR Result

9 122.31 532.6 0.22964 pass

8 243.87 532.6 0.45789 pass

7 366.927 532.6 0.68894 pass

6 491.46 532.6 0.92276 pass

5 635.046 1146.72 0.55379 pass

4 784.9 1146.72 0.68447 pass

3 939.469 1146.72 0.81927 pass

2 1098.346 1146.72 0.95782 pass

1 1260.51 1146.72 1.09923 fail

Corner Column A1 Check

Level Demand(k) Capacity(k) DCR Result

9 55.38 236.7 0.23398 pass

8 120.081 236.7 0.50731 pass

7 184.326 236.7 0.77873 pass

6 248.181 236.7 1.0485 fail

5 314.978 579.65 0.54339 pass

4 382.237 579.65 0.65943 pass

3 449.209 579.65 0.77497 pass

2 516.065 579.65 0.8903 pass

1 582.65 579.65 1.00518 fail

Page | 100

Exterior Column A2 Interior Column B3 Corner Column A1

Figure 5.5.2: Column Eligible for Concrete Jacketing.

5.6: Retrofitting

5.6.1: Retrofitting of Beam by Steel Plating

Beam ID: D34 (Level 01)

Size: 12″×18″

Original Capacity = 108.5 k-ft

Target Capacity = 147.45 k-ft

Page | 101

Steel plate of thickness 1.5 mm i.e. 0.06 inch is added to both tension and compression

face.

So, Depth of steel plate, dp= 0.06 inch

Effective depth of beam, d = Depth of beam – Depth of cover, dc

= (18-2.5) inch

= 15.5 inch

Stress in steel plate in compression and tension, fpc= fpt= 50 ksi

Providing width of steel plate, b = Width of beam – 2(2 inch side cover)

= 12 – 2(2)

= 8 inch

We know,

Strength added by steel plating = compression side + tension side

Compression side = fpc× Apc (𝑑𝑝

2 +d)

Tension side = fpt× Apt (𝑑𝑝

2 + dc)

So, Strength added by steel plating

= [fpc× Apc (𝑑𝑝

2 +d)] + [fpt× Apt (

𝑑𝑝

2 + dc)]

= [50 × (2×0.06×8) × (0.06

2+15.5)] + [50 × (2×0.06×8) × (

0.06

2+2.5)]

=866.88 k-in =72.24 k-ft

Page | 102

So, Capacity after steel plating = Original capacity + 72.24 k-ft

= (108.5+72.24) k-ft

= 180.74k-ft>Target capacity (147.45k-ft)

So, OK

5.6.2: Retrofitting Of Column by Concrete Jacketing

Exterior Column:

Column ID: A2

Level: 06

Size: 13″×13″

Extra gross area for jacketing, Ag= (212 - 132) inch2 = 272 inch2

Capacity increased by concrete jacketing,

Pu= 0.8Φ [0.85fc' (Ag – Ast) + fyAst]

= 0.8×0.7 [0.85×3 (272 – 1.5

100 272) + 50×

1.5

100 272]

= 496.83 kip

Total capacity increased by concrete jacketing

= Original capacity + 496.83 kip

= (335.25 + 496.83) kip

Page | 103

=832.08 kip > Demand (341.79 kip) OK.

Required reinforcement for concrete jacketing,

Ast(required)=1.5

100 272=4.08 inch2

Use 8#7, Ast(provided) = 4.8 inch2> 4.08 inch2 OK.

Figure 5.6.1: Concrete Jacketing of Exterior Column A2.

Interior Column:

Column ID: B3

Level: 01

Size: 23″×23″

Extra gross area for jacketing, Ag= (312 - 232) inch2 = 432 inch2

Capacity increased by concrete jacketing,

Page | 104

Pu= 0.8Φ [0.85fc' (Ag – Ast) + fyAst]

= 0.8×0.7 [0.85×3 (432 – 1.5

100 432) + 50×

1.5

100 432]

= 789.08 kip

Total capacity increased by concrete jacketing

= Original capacity + 789.08 kip

= (1146.72 + 789.08) kip

=1935.80 kip > Demand (1260.51 kip) OK.

Required reinforcement for concrete jacketing,

Ast(required)=1.5

100 432=6.48 inch2

Use 12#7, Ast(provided) = 7.2 inch2> 6.48 inch2 OK.

Figure 5.6.2: Concrete Jacketing of Interior Column B3.

Page | 105

Corner Column:

Column ID: A1

Level: 01

Size: 17″×17″

Extra gross area for jacketing, Ag= (252 - 172) inch2 = 336 inch2

Capacity increased by concrete jacketing,

Pu= 0.8Φ [0.85fc' (Ag – Ast) + fyAst]

= 0.8×0.7 [0.85×3 (336 – 1.5

100 336) + 50×

1.5

100 336]

= 613.73 kip

Total capacity increased by concrete jacketing,

= Original capacity + 613.73 kip

= (579.65 + 613.73) kip

=1193.38 kip > Demand (582.65 kip) OK.

Required reinforcement for concrete jacketing,

Ast(required)=1.5

100 336=5.04 inch2

Use 12#6, Ast(provided) = 5.28 inch2> 5.04 inch2 OK.

Page | 106

Figure 5.6.3: Concrete Jacketing of Corner Column A1.

Corner Column:

Column ID: A1

Level: 06

Size: 11″×11″

Extra gross area for jacketing, Ag= (192 - 112) inch2 = 240 inch2

Capacity increased by concrete jacketing,

Pu= 0.8Φ [0.85fc' (Ag – Ast) + fyAst]

Page | 107

= 0.8×0.7 [0.85×3 (240 – 1.5

100 240) + 50×

1.5

100 240]

= 438.38 kip

Total capacity increased by concrete jacketing,

= Original capacity + 438.38 kip

= (236.7 + 438.38) kip

=675.08 kip > Demand (248.181 kip) OK.

Required reinforcement for concrete jacketing,

Ast(required)=1.5

100 240=3.6 inch2

Use 12#5, Ast(provided) = 3.72 inch2> 3.6 inch2 OK.

Figure 5.6.4: Concrete Jacketing of Corner Column A1.

Page | 108

The detailed calculations of Concrete Jacketing as well as Capacity Check are shown in the following Table 5.6.

Table 5.6: Concrete Jacketing

Position

of

Column

Level Width(in) Height(in) Area(in²)

Total Area

after

Jacketing(in²)

Extra

Gross

Area

(in²)

Capacity

Increased(k)

Original

Capacity(k)

Total

Capacity

Increased(k)

Demand(k) Check

Exterior 6 13 13 169 441 272 496.83 335.25 832.08 341.79 OK

Interior 1 23 23 529 961 432 789.083 1146.7 1935.8 1260.5 OK

Corner 1 17 17 289 625 336 613.731 579.65 1193.38 582.65 OK

Corner 6 11 11 121 361 240 438.379 236.7 675.079 248.18 OK

Page | 109

5.7: Dynamic Analysis (Time History Analysis)

5.7.1: Introduction to EL-CENTRO COMP S90W Ground

Motion

Firstly the model is analyzed using Equivalent Static Force Method. Then the model is

analyzed using Time History Analysis and the response of structure is compared with

that of structure using Equivalent Static Force Method. Here EL-CENTRO COMP

S90W ground motion is used for the analysis.

Data:

(Ground accelerations)

No of data, N =N = 2379

dt = 0.02 sec

Duration =47.56 sec

PGA =2.1 m/s2 = 0.21 g at 3.52 seconds

Page | 110

Figure 5.7.1: EL-CENTRO COMP S90W Ground Motion with PGA Scaled To 0.21g and Duration Equal to 47.56 Seconds.

5.7.2: Structural Models and Their Top Floor Time History

Displacement

Figure 5.7.2: Time History Displacement of the Highlighted Node of Structure.

The above figure shows the time history displacement of the topmost node of the

structure. Similarly time history displacements obtained for other floors in the structure

and the maximum displacement is plotted in the graph. The graphs of structure using

Time History Analysis are compared with that of structure analyzed using Equivalent

Static Force Method.

5.7.3: Comparison of Displacements of Different Floors of

Structure between Dynamic and Static Earthquake Analysis

Table 5.7.1: Comparison of Displacements of Different Floors of Structure between

Dynamic and Static Earthquake Analysis

Level

Displacement(in)

Dynamic Static

9 5.682 3.226

8 5.198 3.047

7 4.491 2.757

6 3.701 2.369

5 2.937 1.897

4 2.425 1.571

3 1.876 1.215

2 1.312 0.838

1 0.731 0.458

Base 0.178 0.12

Figure 5.7.3: Comparison of Displacements along Z-Direction between Dynamic and

Static Earthquake Analysis.

Here in case of top floor level Dynamic Analysis displacement is much greater than

that of Static Analysis. For higher story, displacement will be more for Dynamic

Analysis. So in case of high rise building Time History Analysis should be used to

check the displacement within the limit.

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6

Flo

or

Leve

l

Displacement(in)

dynamic

static

5.7.4: Comparison of Story Drifts of Different Floors of

Structure between Dynamic and Static Earthquake Analysis

Table 5.7.2: Comparison of Story Drifts of Different Floors of Structure between

Dynamic and Static Earthquake Analysis

Story Drift

Level Dynamic Static

9 0.484 0.179

8 0.707 0.29

7 0.79 0.388

6 0.764 0.472

5 0.512 0.326

4 0.549 0.356

3 0.564 0.377

2 0.581 0.38

1 0.553 0.338

Figure 5.7.4: Comparison of Story Drift along Z-Direction between Dynamic and

Static Earthquake Analysis.

Story Drift is the drift of one level of a multistory building relative to the level below.

The greater the drift, the greater the likelihood of damage. According to BNBC

allowable Story Drift at zone 2 is 0.025hsx. hsx is the story height below level x. Here

Story Drift for Static Analysis at top story is 0.179 inch and for Dynamic Analysis it is

0.484 inch. Allowable Story Drift for Static Analysis is 0.25inch which is greater than

0.484 inch in case of Dynamic Analysis. So again it can be said that in case of high rise

building Dynamic Time History Analysis should be performed.

1

2

3

4

5

6

7

8

9

10

0 0.2 0.4 0.6 0.8 1

Flo

or

Leve

l

Story Drift(in)

dynamic

static

5.7.5: Comparison of Story Moment of Different Floors of

Structure between Dynamic and Static Earthquake Analysis

Table 5.7.3: Comparison of Story Moment of Different Floors of Structure between

Dynamic and Static Earthquake Analysis

Story Moment (kip-ft)

Level Dynamic Static

9 76.37 62.43

8 115.97 68.99

7 142.3 83.41

6 154.25 92.98

5 124.9 110.76

4 137.69 112.88

3 136.8 117.14

2 139.2 121.86

1 155.38 115.76

Figure 5.7.5: Comparison of Story Moment along Z-Direction between Dynamic and

Static Earthquake Analysis (A4 column).

From the figure it is seen that moment due to Dynamic Analysis is greater than the

Static Analysis. Here at level 06 there is a huge jump of moment due to Dynamic Time

History Analysis. Member fails in maximum reinforcement. So member size should be

increased. Similarly other columns are also analyzed and it is found that member exceed

its maximum reinforcement limit.

1

2

3

4

5

6

7

8

9

10

0 50 100 150 200

Flo

or

Leve

l

Moment(k-ft)

dynamic

static

CHAPTER 6

CONCLUSION AND

RECOMMENDATION

In this research study seismic evaluation and retrofitting are done for a typical existing

building in Dhaka city which was constructed before 1990. As the reinforcement details

of the building were not available, firstly the design of the building is carried out for

Dead Load and Live Load only without the consideration of seismic or wind load.

Secondly the building is analyzed considering Seismic Load in addition to Dead Load

and Live Load. Equivalent Static Force Method is used according to BNBC 1993 for

applying Earthquake Load. Design software STAAD-Pro is used for 3D analysis. Then

Demand Capacity Ratio (DCR) is calculated to evaluate the members for Seismic

Loads. Retrofitting procedure is done for the members that are failed under Seismic

Loads. Finally the comparisons between Dynamic and Static behavior are also shown.

Based on the seismic evaluation carried out in this study, the following important

conclusions can be made-

All of the beams and columns in one unit were checked for vulnerability due to

seismic loads. In total, there are 216 beams in the building in one unit. Among

them 64 beams are failed after applying earthquake force. It means 29.63%

beams are failed.

On the other hand there are 144 columns in the building in one unit. Among

them 21 columns are failed after applying earthquake force. It means 14.58%

columns are failed.

Maximum DCR for beams is found to be 1.373 at Level 02 which is 37.3%

greater than the capacity. Similarly maximum DCR for column is found 1.09923

at Level 01 which is 9.923% greater than the capacity.

For providing retrofitting measures of the deficient members Steel Plating

Method is applied for the beams and Concrete Jacketing Method is applied for

the columns.

In case of retrofitting of beam by Steel Plating it is found that the capacity

achieved by retrofitting method is 180.74 k-ft which is more than the target

capacity of 147.45 k-ft. The capacity increase is 22.58%.

On the other hand, in case of retrofitting of interior column by Concrete

Jacketing, the capacity achieved by retrofitting method is 1935.80 kip which is

more than the demand 1260.51 kip. The capacity increase is 53.57%.

Finally based on this research study, it is recommended that the buildings which were

not built with seismic consideration can be evaluated and retrofitted following the thesis

procedure presented in this study.

`

CHAPTER 7

REFERENCES

1. Design Of Concrete Structures

Thirteen Edition

Written by Arthur H. Nilson, David Darwin and Charles W. Dolan.

2. BNBC (Bangladesh National Building Code) 1993.

3. http://Theconstructor.Org/Structural-Engg/Strengthening-Of-R-C-

Beams/1930/

4. http://news.nationalgeographic.com/news/2013/13/130425-bangladesh-dhaka-

building-collapse-world/

5. Seismic Evaluation Of Institute Building NIT Rourkela,

Ankur Agrawal

Department Of Civil Engineering

National Institute Of Technology (09th May 2012).

6. Earthquake Resistant Design Of Structures

Pankaj Agarwal, Manish Shrikhande

PHI Learning Private Limited, 2011.

7. Seismic Evaluation And Retrofitting Of Buildings And Structures

N. Lakshmanan

ISET Journal of Earthquake Technology,

Paper No. 469, 31-48, March-June 2006.

8. Seismic Evaluation And Retrofit Of Reinforced Concrete Buildings

Applied Technology Council (1996)

Report ATC 40 / SSC 96–01, Palo Alto.

9. Structural Analysis, Modeling, And Design Of A Reinforced Concrete Afghan

School Under Severe Earthquake Motions

Mohammad Zekria

Master Of Science In Civil Engineering

San Diego State University, 2011.

10. Seismic Evaluation Of Existing Reinforced Concrete Building

Dinesh J.Sabu, Dr. P.S. Pajgade (June-2012).

11. Seismic Evaluation And Strengthening Of Existing Buildings

Durgesh C. Rai

IITK-GSDMA –EQ24-V2.0.

12. Standard Methods For Seismic Analyses

Joao Luis Domingues Costa

Report BYG.DTU R-064, 2003.

13. Seismic Design Of Building Structures(9th edition)

Lindeburge, M. R., and K. M. Mcmullin

A Professional’s Introduction to Earthquake Forces and Design Details

Saddle River, New Jersey: Professional Publications, 2008.

14. A National Policy For Seismic Vulnerability Assessment Of Buildings And

Procedure For Rapid Visual Screening Of Buildings For Potential Seismic

Vulnerability

Prof. Ravi Sinha And Prof. Alok Goyal

Department Of Civil Engineering, Indian Institute Of Technology Bombay,

2011.

15. Design Of Earth-Quake Resistant

Multi-Storied Rcc Building On A Sloping Ground

Saptadip Sarkar

Department Of Civil Engg.

National Institute Of Technology, Rourkela (2010)

16. A Major Project Report On Effect Of Configuration Of R.C.C. Building

Subjected To Seismic Loading

Abhishek Kumar Gupta

M. E. (Structural Engineering)

Department Of Civil &Environment Engineering

Delhi College Of Engineering (Now Known As Delhi Technological University

(2011)

17. Seismic Evaluation And Retrofit Of A Rc Frame Structure

Praval Priyaranjan

B.Tech

Department Of Civil Engineering

N.I.T Rourkela (May, 2012)

……….The End..........