complete thesis

MULTI-DYNAMIC ANALYSIS AND DESIGN OF A TALL

BUILDING

A Thesis submitted in partial fulfillment of the

requirement for the degree

of

M.Tech (Structural Engineering)

by

SYED ABBAS AHMED

(10MST0023)

SCHOOL OF MECHANICAL AND BUILDING SCIENCES

Vellore – 632 014, Tamil Nadu

May 2012

SCHOOL OF MECHANICAL AND BUILDING SCIENCES

BONAFIDE CERTIFICATE

This is to certify that the thesis entitled “MULTI-DYNAMIC ANALYSIS

AND DESIGN OF A TALL BUILDING” is submitted by SYED ABBAS

AHMED, (10MST0023) to the School of Mechanical and Building Sciences , VIT

University, Vellore, for the award of the degree in M.Tech is a bonafide record of

work carried out by him under my supervision. The contents of this thesis, in full or

in parts have not been submitted to any other Institute or University for the award of

any degree or diploma.

Guide Programme Manager

Internal Examiner External Examiner

i

ACKNOWLEDGEMENT

I sincerely express thanks to our Chancellor Dr. G.Viswanathan for all the facilities provided

by him for our course and project work.

My sincere thanks to our Vice Presidents Mr. Sankar Viswanathan and Mr. G. V. Sampath

and Vice Chancellor for the consistent encouragement shown to us

throughout our college days.

I am greatly benefited under the invaluable guidance, efficient supervision, encouragement and

informative suggestions of my guide Dr. A. Sivakumar Professor, SMBS, VIT University.

My sincere thanks to our revered Dr. A.S.Santhi, Director, SMBS for his kind encouragement

for all our endeavours upon this project.

I am deeply indebted to Dr.G.Mohan Ganesh, Programme Manager, Structural &

Geo-Technical division, VIT University, Vellore.

I also extend my thanks to Review committee for giving me valuable suggestions throughout the

various phases of review in this project work.

Lastly I would like to extend my special thanks to Imtiyaz Baadil and Rameshwar Prasad for

their invaluable time, my gratitude and thanks goes out to them.

I also wish to thank my parents, friends, professors, Teaching & Non-teaching staff of Structural

& Geo technical division, VIT University, Vellore for the encouragement rendered to me for the

successful completion of the project

Syed Abbas Ahmed

ii

CONTENTS

Page No.

ACKNOWLEDGEMENT i

ABSTRACT ix

LIST OF TABLES iv

LIST OF FIGURES vi

CHAPTER 1 INTRODUCTION

1.1 Background 1

1.2 Objective of Project 1

1.3 Scope of Project 1

CHAPTER 2 LITERATURE REVIEW 2

CHAPTER 3 GEOMETRY AND LAYOUT 3

CHAPTER 4 ANALYSIS PARAMETERS 5

4.1 Building Modeling

4.2 Input Parameters

CHAPTER 5 LOADINGS 6

5.1 Gravity Loads 6

5.1.1 Loads on Beams 6

5.1.2 Loads on Slabs 6

5.1.3 Wind Loads 6

5.1.4 Earthquake Loads 7

5.2 Software Used 7

5.2.1 ETABS GUI 7

5.2.2 Analysis and design results 7

5.2.3 Assumption of section and material 7

CHAPTER 6 MODAL ANALYSIS RESULTS 9

CHAPTER 7 WIND ANALYSIS RESULTS 11

7.1 Pre-Analysis Inputs 12

7.2 Storey Shear 13

7.3 Storey Drift 13

7.4 Column results 14

iii

7.5 Beam results 23

7.6 Shear wall results 25

CHAPTER 8 SEISMIC ANALYSIS AND DESIGN 28

8.1 Static Earthquake analysis 28

8.2 Elastic Time-History analysis 28

8.3 Storey Drift 29

CHAPTER 9 ANALYSIS AND DESIGN DETAILS 30

9.1 Column details 30

9.1.1 Design details of C-19 32

9.1.2 Analysis results of C-18 38








9.2 Time-History Analysis details 59

9.2.1 Pseudo Spectral Acceleration curve 59

9.2.2 Joint Displacement curve 59

9.2.3 Spectral Displacement curve 60

9.3 Shear wall analysis and design 61

9.3.1 Shear wall analysis results 61

9.3.2 Shear wall design 62

9.4 Beam analysis and design details 69

9.4.1 General requirements 70

9.4.2 Bending moments and shear forces 70

CHAPTER 10 CONCLUSION 81

APPENDICES 83

PUBLICATION 84

REFERENCES 84

iv

LIST OF TABLES

Table No Title Page No

1 Load intensity 6

2 Load combinations 7

3 Properties of material used 8

4 Assumed sections for preliminary

analysis 8

5.1 Modal analysis data 9

5.2 Modal participation data 10

5.3 Mode information 10

6.1 Wind parameters 12

6.2 Storey shear 13

6.3 Storey drifts 14

7.1 Static analysis results 28

7.2 Storey shear 29

7.3 Storey drifts 30

8.1 Design forces in shear wall 61

9.1 End moments for 1-1 beams 71

9.2 End shears for 1-1 beams 71

9.3 B23 percentage rebar distribution 72










10.4 End moments for A-A beams 76

10.5 End shears for A-A beams 76



10.8 End moments for B-B beams 77

10.9 End shears for B-B beams 77


v


11.2 End moments for C-C beams 79

11.3 End shears for C-C beams 79



vi

LIST OF FIGURES

Figure No Title Page No.

2.1 Plan of the building 3

6.3 Deformation of the structure for Mode-1 10

7.0 Columns and beams location 11

7.1 Wind analysis in ETABS 12

7.2 Column labels 15

7.3 Column-19 15

7.4 Axial Load v/s Storey level for C-19 16

7.5 Storey level v/s Moment-xx for C-19 16

7.6 Storey level v/s Moment-yy for C-19 17

7.7 Column-18 17




7.11 Column-23 19




7.15 Column-27 21




7.19 Critical beam location 23

7.20 Beam on dead load 24

7.21 Beam on load combination 24

7.22 Elevation of shear wall 25

7.23 Resultant Fmax of shear wall at X 26

7.24 Resultant Fmax of shear wall at Y 27

8.1 Accelerogram of Bhuj Earthquake 28

9.1 Column-19 30




9.5 Column-18 38



vii

9.8 Column-23 43




9.12 Column-24 49




9.16 Column-27 53




9.20 Time Period v/s PSA curve 59

9.21 Time v/s Joint Displacement curve 59

9.22 Time Period v/s Spectral Displ.curve 60

9.23 Shear wall loads 61

9.24 Reinforcement details in RCC shear wall 69

9.25 Beam layout plan 69

9.26 Beam profile 71

9.27 Reinforcement details for B23 72












viii

NOMENCLATURE

Sr No. SYMBOL NOTATIONS

1. τv nominal shear stress

2. τc design shear stress of concrete

3. τcmax maximum shear stress

4. Vu Shear force

5. tw thickness of web

6. dw depth of wall

7. lw length of wall

8. Muv moment of resistance

9. fy yield strength of steel

10. fck characteristic strength of concrete

11. Es elastic modulus of steel

12. Pu axial load

13. Ast area of steel

14. Ac area of concrete

15. Iy moment of inertia about yy-axis

16. Mx moment about xx-axis

17. My moment about yy-axis

18. b breadth of beam

19. D depth of beam

20. Lc length of column

ix

ABSTRACT

The dynamical behaviour of civil engineering structures has traditionally been tackled, for design

purposes, in an ‘equivalent static’ way. Today, with the availability of softwares, we are able to

deal explicitly with dynamic analysis of realistic structures with many (dynamic) degrees of

freedom, as well as the outcome of the valuable research carried out in the various fields

included under ‘Dynamics’, make this type of analysis a part of everyday life in the design

office. This project serves to research on the dynamic seismic and wind analysis of a tall R.C.C

framed building subjected to wind and earthquake excitation using software. The main objective

of this research is to study the dynamic responses due to the gravity, seismic and wind excitation

on a high rise building and its respective responses to it. Analysis results of the R.C.C framed

high rise model have been studied and accordingly optimum economical sections are provided as

much as possible, sections suitable for both seismic and wind excitations. Gravity loads

confirming to IS 875-1987 (Part-1 and Part-2), Wind load parameters from IS 875-1987 (Part-3)

and Earthquake loading parameters from IS 1893-2002. A + shaped structure was analyzed and

designed, such that the various structural members like beam, column and shear wall are

economically designed using design based on IS 456-2000, to resist both the dynamic lateral

loads of seismic and wind.

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

The term dynamic may be defined simply as time varying; thus a dynamic load is any load of

which its magnitude, direction, and/or position varies with time. Similarly, the structural

response to a dynamic load,

i.e., the resulting stresses and deflections, is also time varying, or dynamic. Two basically

different approaches are available for evaluating structural response to dynamic loads:

deterministic and nondeterministic. The choice of method to be used in any given case depends

upon how the loading is defined. If the time variation of loading is fully known, even though it

may be highly oscillatory or irregular in character, it is referred as a prescribed dynamic loading;

and the analysis of the response of any specified structural system to a prescribed dynamic

loading is defined as a deterministic analysis. On the other hand, if the time variation is not

completely known but can be defined in a statistical sense, the loading is termed a random

dynamic loading; and its responding analysis of response is defined as a nondeterministic

analysis. In this project, the loading prescribed is dynamic loading, due to the pre-prescribed

excitations given to the framed building structure.

In today’s day and age, with increasing natural disasters witnessed all around the globe, it is of

prime importance to intricately analyse and design important structures for dynamic loads

expected or unexpected on it.

1.2 OBJECTIVE OF PROJECT

The objective of the project is to fully design and optimize a R.C.C framed tall building and to

track the behaviour of various structural components of the same for different loadings.

1.3 SCOPE OF THE PROJECT

To achieve the above objectives the project is scheduled as below:

To establish the geometry of the structure based on the various criteria.

To determine the characteristic loadings and their occurrences.

Analysis of structure taking into account vertical and lateral loadings.

Elastic Time-History analysis of critical components in the structure.

Design of various structural components using IS-456 (2000) and IS-13920 (1993).

Optimization of various structural components.

2

CHAPTER 2

LITERATURE REVIEW

Some of the literatures reviewed are shown in brief below:

Seismic Analysis of the world’s second tallest building

Taipei 101 with 101 stories and 508 m height, located in Taipei where earthquakes and strong

typhoons are common occurrences. The structure of the building is a mega-frame system

composed of concrete filled steel tube (CFT) columns, steel brace core and belt trusses, which re

combined to resist vertical and lateral loads. An earthquake spectrum was generated for the

location, which was adopted to calculate the lateral displacements and distributions of interior

column forces. Time History analysis of elastic and inelastic seismic response was carried out.

Full scale measurements of wind effects on tall buildings

This paper describes the results obtained from the measurements of win effects on two tall

buildings with 70-storeys and 30-storeys. The field data presented is wind velocity and

acceleration response measured at the top of the tall building. The damping characteristics which

were obtained by using decrement technique

Wind engineering challenges of the new generation of super-tall buildings

The new challenges posed by tall buildings are discussed in this paper. The statistics of wind

speed and direction used in wind engineering have been almost entirely based on records from

ground based meteorological stations. The aerodynamics of tall buildings can gave a huge impact

on their cost. Wind affects not only the structural integrity of the tower but also its serviceability.

The book titled ‘Wind and Earthquake Resistant Buildings Structural analysis and design’

by S.Taranah Bungale has been quite successful in the discussion of modern design codes,

comprehensive coverage of material properties, a full discussion of assessment of loading and its

importance in assessing safety of designs.

The book mainly covers the basic aspect of design along with a detailed explanation on the UBC,

ASCE and IBC codes of design.

3

CHAPTER 3

GEOMETRY AND LAYOUT

The building comprises of 15 storeys, each storey with a height of 3.1 meters. Total height of the

building comprising of 49.6 meters.

G + 15 R.C.C building structure with 12x12 square meters building block compartments. With

total width of 36 meters. Total area of 720 m2.

Fig 2.1: Plan of the Building

Each square block comprising of 9 columns, bringing the total number of columns to 16 columns

in all and 4 columns at core wall acting as boundary elements for the shear wall. Though it is not

necessary to provide flange it is recommended by IS 13920:1993 (clause 9.4). Boundary element

is the portion along the wall edges that is strengthened by longitudinal and transverse

reinforcement. Here the boundary element provided is of 750x750mm.

This building is a dual system structure with SMRF (Special Moment Resisting Frame) and

Ductile Shear Wall. In buildings where a space frame resists the earthquake forces, the columns

and beams act in bending. During a large earthquake, story-to-story deflection (story drift) may

be accommodated within the structural system without causing failure of columns or beams.

However, the drift may be sufficient to damage elements that are rigidly tied to the structural

system such as brittle partitions, stairways, plumbing, exterior walls, and other elements that

4

extend between floors. Therefore, buildings can have substantial interior and exterior non-

structural damage and still be structurally safe. Although there are excellent theoretical and

economic reasons for resisting seismic forces by frame action, for particular buildings, this

system may be a poor economic risk unless special damage-control measures are taken.

A shear wall (or braced frame) building is normally more rigid than a framed structure. With low

design stress limits in shear walls, deflection due to shear forces is relatively small. Shear wall

construction is an economical method of bracing buildings to limit damage, and this type of

construction is normally economically feasible up to about 5 stories. Notable exceptions to the

excellent performance of shear walls occur when the height-to-width ratio becomes great enough

to make overturning a problem and when there are excessive openings in the shear walls. Also, if

the soil beneath its footings is relatively soft, the entire shear wall may rotate, causing localized

damage around the wall. The structural systems just mentioned may be used singly or in

combination with each other. When frames and shear walls interact, the system is called a dual

system if the frame alone can resist 25% of the lateral load. Otherwise, it is referred to as a

combined system. The type of structural system and the details related to the ductility and

energy-absorbing capacity of its components will establish the Response reduction factor R, used

for calculating the total base shear.

As for the shear wall

5

CHAPTER-4

ANALYSIS PARAMETERS

4.1 BUILDING MODELLING

The model was first given trial sections for the structural members and was analyzed for the

same. After numerous numbers of trials and errors, the dimensions of the structural members

were decided. The static and dynamic analysis was carried out on the model with the given

sections assigned to it. Column members modelled initially with a cover of 45mm to steel rebar.

Beam section members were given 30mm clear cover to the steel rebar.

Slab was modeled as a Rigid Diaphragm, since the slab does not contribute in resisting the story

shear. Also the rigid diaphragm does not change its plan shape when subjected to lateral loads. It

remains the same size, and square corners remain square. There is no flexure; rigid diaphragms

are capable of transmitting torsion to the major resisting elements (usually the outermost

elements). The lateral story shear is distributed to the resisting elements in proportion to the

rigidities of those elements.

Shear Wall was modeled as a Shell element, which combines both in-plane and out-of-plane

stiffness. Also the shear wall is provided with flange sections at its ends acting as boundary

elements to the wall. Boundary elements are portions along the wall edges are strengthened by

longitudinal and transverse reinforcement. Furthermore it is recommended by IS 13920:1993 to

provide shear walls with flanges with greater dimension than the wall itself as boundary

elements.

Furthermore, the slab element has been meshed into finer elements of 1x1 meter dimension, for

better and accurate load distribution on the beam members. M25 grade concrete was adopted for

the horizontal members like slab and beams. M30 grade concrete was adopted for the vertical

members like columns and Shear Wall.

4.2 INPUT PARAMETERS

Earthquake Parameters:

Seismic zone considered – Zone V

Soil Type – Soft soil

Importance Factor – High

Response reduction factor – 5

Wind Parameters:

Terrain Category – 3

Structure class – B

Risk co-efficient – 1.08

Windward Co-efficient – 0.8

Leeward Co-efficient – 0.5

For Seismic Dynamic analysis, Linear Time-History analysis is done to the building structure.

Accordingly the behavior of the building has been studied and designed for.

6

CHAPTER 5

LOADINGS

Various Indian Codes like IS 875 (Part-1, 2 and 3), IS 1893(Part-1):2002 have been referred to

decide the quantum of loading to be given to the structure.

5.1.2 GRAVITY LOADS

5.1.2.1 Loads on Beams

The imposed loading applicable to the beams and slabs are given in IS 875 (Part-1)-1975,

The brick wall load on the beam was calculated based on the height per meter length of the wall.

Density of brick wall = 1805 Kg/m3 (Using sand cement bricks)

Cement Plaster = 1040 Kg/ m3

----------------

Total = 2845 Kg/ m3

Height of the wall = 3.1 m

Weight per meter of Brick-wall = 3.1 x 2.845 = 9 KN/m.

Uniformly distributed load of 9 KN/m on the beams from brick-wall acting as dead load on the

structure.

5.1.2.2 Loads on Slab

Dead load on slab element has been taken as 2 KN/m and 2KN/m as Live load on the slab

element (since the building structure is a residential complex).

Table-1

LOADING INTENSITY

Dead Load 2 KN/m

Live Load 2 KN/m

5.1.3 WIND LOADS

The location of the building structure is Bhuj, Gujarat. The wind speed suggested by IS 875

(Part-3):1975 is 50m/s for this location. The wind exposure is from the extents of the rigid

diaphragms assigned to the slab elements. Also IS 1893(Part-1):2002 states that wind is not to be

considered simultaneously with earthquake or maximum flood or maximum sea waves.

The load case combinations adopted are referred from IS 875 (Part-3):1975,

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L – Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L – Wy)

1.5 (D.L + Wx)

7

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

5.1.4 EARTHQUAKE LOADS

Seismic forces are the most decisive and critical loadings for a multi storey building. The

structure is seismically loaded using elastic time-history method and load combinations

specified by the code are used. The structure is assumed to be in Bhuj with the soil being soft

soil. The direction scales are calculated taking the importance factor (I) as 1.5 and reduction

factor (R) as 5. The load case combinations adopted are referred from IS 1893 (Part-1):2002,

Table-2

STATIC DYNAMIC

1.2 (D.L + L.L + EQx)

1.2 (D.L + L.L – EQx)

1.2 (D.L + L.L + EQy)

1.2 (D.L + L.L – EQy)

1.5 (D.L + EQx)

1.5 (D.L - EQx)

1.5 (D.L + EQy)

1.5 (D.L - EQy)

1.2 (D.L + L.L + THx)

1.2 (D.L + L.L – THx)

1.2 (D.L + L.L + THy)

1.2 (D.L + L.L – THy)

1.5 (D.L + THx)

1.5 (D.L - THx)

1.5 (D.L + THy)

1.5 (D.L - THy)

5.2 SOFTWARES USED

This chapter deals with the brief description of the software used in the project with

programmatic representations of the GUI of the software.

5.2.1 ETABS GUI (GRAPHICAL USER INTERFACE)

ETABS is a structural analysis and design computer program. The basic three activities

performed by the software are a) model generation b) analysis c) design. All the above activities

are facilitated by tools contained in the program’s graphical environment. ETABS can analyse

and design various structural elements as per design standards of various countries like USA,

Britain, India, Japan etc. Dynamic analysis like response spectrum analysis and time history

analysis can also be carried out. ETABS stands for: Extended Three-Dimensional analysis of

building structures. ETABS has been recognized as the industry standard for Building Analysis

and Design Software. Building information system built around a physical object based graphical

user interface. Powered by targeted special purpose algorithms for analysis and design, specially

used for dynamic analysis.

8

5.2.2 ANALYSIS AND DESIGN RESULTS

In ETABS results can be obtained in many forms such as moments, shear forces, mode shapes

etc. for different load cases. Design is also carried as per various codes. Commands like

grouping, section overwrites, greatly reduce the time taken to arrive a safe section in the building

structure.

5.3 ASSUMPTION OF SECTION AND MATERIAL

The multi-storey building is entirely made of R.C.C members. For analysis of the same in

ETABS, the following properties shown in table-3 of the materials have been adopted.

Table-3 PROPERTIES OF THE MATERIAL USED

CONCRETE (KN-m)

M25 M30

fck = 25 N/mm2

Isotropic Material

Mass per unit Volume = 2.4

Weight per unit Volume =24

Modulus of Elasticity = 25 x 106

Poisson’s Ratio = 0.2

Co-eff of Thermal Expansion = 9.9 x 10-6

Shear Modulus = 10.41 x 106

fck = 30 N/mm2

Isotropic Material

Mass per unit Volume = 2.4

Weight per unit Volume =24

Modulus of Elasticity = 25 x 106

Poisson’s Ratio = 0.2

Co-eff of Thermal Expansion = 9.9 x 10-6

Shear Modulus = 10.41 x 106

Structural components like beams and columns which constitute the structural frame have been

assumed initially and the structure is analysed taking into account permissible deflections. The

following sections shown in table 4 were assumed.

TABLE-4 ASSUMED SECTIONS FOR PRELIMINARY ANALYSIS

SLAB SHEAR WALL BEAM COLUMN

Thickness – 150 mm Thickness – 300mm 400x650 mm 750x750 mm

9

CHAPTER 6

MODAL ANALYSIS RESULTS

The elastic properties and mass of building causes it to develop a vibratory motion when they are

subjected to dynamic action. The vibration of a building consists of a fundamental mode of

vibration and the additional contribution of various modes, which vibrates at higher frequencies.

In low-rise buildings the seismic response depends primarily on the fundamental mode of

vibration, the also the period of vibration of this mode expressed in modes is the most

representative characteristics of the dynamic response of a building. On the basis of time period,

building structures are classified as –

i) Rigid (T < 0.3 sec).

ii) Semi-Rigid (0.3 sec < T < 1.0 sec).

iii) Flexible (T > 1.0 sec).

Buildings with lower natural frequencies and long natural periods, these buildings will

experience lower accelerations but larger displacements. The model is analyzed for 45 numbers

of modes. The type of analysis being chosen as Ritz Vector analysis over Eigen Vector analysis.

Reason being Ritz vector analysis is that it provides a better participation factor, which enables

the analysis to run faster, with the same level of accuracy. Further, missing-mass modes are

automatically included, there is no need to determine whether or not there are enough modes,

and when determining convergence of localized response with respect to the number of modes,

Ritz vectors converge much faster and more uniformly than do Eigen vectors. Ritz vectors are

not subject to convergence questions, though strict orthogonality of vectors is maintained, similar

to Eigen vectors. The Ritz load vectors assigned are as accelerations in X, Y and Z-directions to

the building structure.

Mode

Period

T(in sec)

Frequency

ὠ (Hz)

1 2.107427 0.4745123

2 2.107427 0.4745123

3 2.067215 0.4837426

4 0.66899 1.4947907

5 0.562153 1.7788751

6 0.562153 1.7788751

7 0.381305 2.6225725

8 0.261898 3.8182804

9 0.261898 3.8182804

10 0.257269 3.8869821

11 0.187375 5.3368913

12 0.159323 6.2765577

13 0.159323 6.2765577

14 0.143056 6.9902695

15 0.112865 8.8601426

Table -5.1

10

Type Accel StatPercent DynPercent

Accel RX 100 100

Accel RY 100 100

Accel RZ 99.9999 99.8222

TABLE-5.2

Fig 6.3: Deformation of Structure at Mode-1

TABLE-5.3

Mode Period UX UY UZ SumUX SumUY SumUZ RX RY RZ SumRX SumRY SumRZ

1 2.107427 1.6316 69.3565 0 1.6316 69.3565 0 97.1324 2.2851 0 97.1324 2.2851 0

11

CHAPTER 7

WIND ANALYSIS RESULTS

Analysis of the structure yielded the following results. Critical loads were noted down for

various structural components like beams columns, shear wall, etc.

The results of the static wind analysis are shown in the following pages for columns, beams and

shear wall. The different beams and columns locations are shown in the figure below. Since the

structure in symmetrical in plan, the analysis results of beams and column sections of one side of

the building structure is discussed. The reason being that, the results will be same for the other

columns sections as well.

Fig 7.0 Column and beam locations

The shear wall located at the center as a core wall, provided with flange section acting as

boundary elements. Various analysis results are shown in the following pages, on the effect of

wind on the building structure.

In ETABS automatically calculated wind loads are only applied to rigid diaphragms. A separate

load is created for each rigid diaphragm present at a story level. The wind loads calculated at any

story level are based on the story level elevation, the story height above and below that level, the

assumed exposure width for the rigid diaphragm(s) at that story level and various code dependent

wind coefficients.

When specifying the wind direction you indicate the direction of the wind by an angle measured

in degrees. An angle of 0 degrees means the wind is blowing in the positive global X-direction

12

that is blowing from the negative global X-direction to the positive global X-direction. An angle

of 90 degrees means the wind is blowing in the positive global Y-direction. An angle of 180

degrees means the wind is blowing in the negative global X direction. An angle of 270 degrees

means the wind is blowing in the negative global Y-direction. You can input any angle for the

wind direction. The angle is always measured counter clockwise from the positive global X-axis.

A positive angle appears counter clockwise as you look down on the model in the negative

global Z-direction.

7.1 PRE-ANALYSIS INPUTS

Fig 7.1: WIND ANALYSIS IN ETABS

TABLE 7.1 : WIND PARAMETERS

CODE IS 875:1987

EXPOSURE From extents of rigid diaphragms

WINDWARD COEFFICIENT 0.8

LEEWARD COEFFICIENT 0.5

EXPOSURE HEIGHT 49.6 meters

WIND SPEED 50 m/s

TERRAIN CATEGORY 3

STRUCTURE CLASS B

RISK COEFFICIENT 1.08

TOPOGRAPHY FACTOR 1

13

7.2 STOREY SHEAR

The following storey shears were obtained from this method as depicted in table 5.2.

Maximum base shear was observed in X and Y direction with an intensity of 3881.17 KN.

Where X and Y directions are the orthogonal horizontal directions. In ETABS the X and Y axis

are taken as the orthogonal horizontal directions and Z axis as the vertical direction.

7.3 STOREY DRIFT

Storey drift is the displacement of one level relative to the other level above or below. This is

one of the most important parameter of lateral analysis to be studied. As per clause no. 20.5 of

IS 456:2000, the lateral sway at the top should not exceed H/500, where H is the total height of

the building.

500

H

500

6.49 m0.0992 meters = 99.2 mm.

TABLE 6.2: STOREY SHEAR

FLOOR

PEAK STOREY

SHEAR IN KN

X Y

16 149.6 149.6

15 445.4 445.4

14 736.12 736.12

13 1021.82 1021.82

12 1302.53 1302.53

11 1578.29 1578.29

10 1848.99 1848.99

9 2112.81 2112.81

8 2368.68 2368.68

7 2616.65 2616.65

6 2854.79 2854.79

5 3080.44 3080.44

4 3290.17 3290.17

3 3488.03 3488.03

2 3684.6 3684.6

1 3881.17 3881.17

14

TABLE 6.3: STOREY DRIFT

STOREY

LEVEL WX 1.2 (D.L + L.L + WX) 1.5 (D.L + WX)

16 .356 .428 .535

15 .374 .449 .561

14 .399 .448 .599

13 .421 .506 .632

12 .442 .532 .664

11 .463 .556 .695

10 .48 .576 .720

9 .491 .59 .738

8 .496 .596 .745

7 .492 .591 .738

6 .476 .571 .714

5 .446 .535 .669

4 .399 .479 .599

3 .332 .399 .499

2 .243 .292 .365

1 .117 .141 .176

All values above are in mm

Since all the storey drifts are under the limits prescribed by IS 456:2000, the building is safe

against storey drift for lateral loading of wind on it.

7.4 COLUMN RESULTS

There are 32 columns in total in each storey. Amounting up to 512 columns in the complete

building structure.

In the following pages, the results for the various columns are shown, graphs plotted of:

i) Storey level v/s Axial Load.

ii) Storey level v/s Moment-X (moment acting on minor axis of column).

iii) Storey level v/s Moment-Y (moment acting on the major axis of column).

The graphs plotted are for the various prescribed load combinations suggested by

IS 875 (Part-3)-1975. The graphs plotted give us an idea about the moments acting on the

column member and helps in designing the structural member by taking the envelopes of all the

loading combinations.

15

Fig 7.2 Column labels

For simplicity, we are considering the similar columns sections in the building structure and

plotting the graphs for different forces against the storey levels. Furthermore, since the building

is symmetrical in plan dimensions, the columns grouped in the following manner tend to behave

in a similar manner.

Fig 7.3 Column-19

16

Fig 7.4 Axial Load v/s Storey level

Maximum Axial Load @ ground level = 9720 KN for 1.5(D.L + L.L).

Fig 7.5 Storey level v/s Moment-xx

Maximum Moment @ top storey = -272 KN for 1.5 (D.L + Wx)

0123456789

10111213141516

-12000-10000-8000-6000-4000-20000

C-19 Axial Load v/s Storey level

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

1.5 (D.L + L.L )

Axial Load ------→

←

S

t

o

r

e

y

L

e

v

e

l

0

2

4

6

8

10

12

14

16

-300 -200 -100 0 100 200 300

C-19 Storey level v/s Moment-X

1.2 (D.L + L.L + Wx)

1.5 (D.L + L.L )

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

← Moment →

←

S

t

o

r

e

y

L

e

v

e

l

17

Fig 7.6: Storey level v/s Moment-yy

Maximum Moment @ top storey = -271 KN-m for 1.5(D.L+Wx)

Fig 7.7: Column-18

0

2

4

6

8

10

12

14

16

-300 -200 -100 0 100 200 300

C-19 Axial Load v/s Moment-Y

1.5 (D.L + L.L )1.2 (D.L + L.L + Wx)1.2 (D.L + L.L - Wx)1.2 (D.L + L.L + Wy)1.2 (D.L + L.L - Wy)1.5 (D.L + Wx)1.5 (D.L - Wx)1.5 (D.L - Wy)

← Moment →

←

S

t

o

r

e

y

L

e

v

e

l

18

Fig: 7.8 Axial Load v/s Storey level

Maximum Axial Load @ ground level = 9846 KN for 1.5(D.L+L.L)

Fig: 7.9 Storey level v/s Moment-xx

Maximum moment @ ground level = -170 KN-m for 1.5(D.L-Wx)

0123456789

10111213141516

-12000-10000-8000-6000-4000-20000


1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

←

S

t

o

r

e

y

L

e

v

e

l


0

2

4

6

8

10

12

14

16

-200 -100 0 100 200 300

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)



←

S

t

o

r

e

y

L

e

v

e

l

19

Fig: 7.10 Storey level v/s Moment-yy

Maximum moment @ ground storey = 152 KN-m for 1.5(D.L+Wy).

Fig: 7.11 Column-23

0

2

4

6

8

10

12

14

16

-200 -100 0 100 200

C-18 Storey level v/s Moment-Y

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)


←

S

t

o

r

e

y

L

e

v

e

l

20


Maximum Axial Load @ ground storey = 10605 KN for 1.5(D.L+L.L).

Fig: 7.13 Storey Level v/s Moment-xx

Maximum moment @ top storey = -123 KN-m for 1.5(D.L+Wx).

0

2

4

6

8

10

12

14

16

18

-12000-10000-8000-6000-4000-20000


1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

←

S

t

o

r

e

y

L

e

v

e

l


0

2

4

6

8

10

12

14

16

-300 -200 -100 0 100 200


1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

←

S

t

o

r

e

y

L

e

v

e

l

← Moment →

21

Fig: 7.14 Storey Level v/s Moment-yy

Maximum moment @ ground storey = -150.562 KN-m for 1.5(D.L-Wy).

Fig: 7.15 Column-27

0

2

4

6

8

10

12

14

16

-200 -100 0 100 200

C-23 Storey level v/s Moment-Y

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

← Moment →

←

S

t

o

r

e

y

L

e

v

e

l

22


Maximum Axial Load @ ground level = 5675 KN for 1.5(D.L+Wy).

Fig: 7.17 Storey Level v/s Moment-xx

Maximum moment @ top storey = -138.45 KN-m for 1.5(D.L+Wx).

0

2

4

6

8

10

12

14

16

-6000-4000-20000

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

←

S

t

o

r

e

y

L

e

v

e

l


0

2

4

6

8

10

12

14

16

-400 -300 -200 -100 0 100 200

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

←

S

t

o

r

e

y

L

e

v

e

l

← Moment →

23

Fig 7.18: Storey Level v/s Moment-yy

Maximum moment @ top storey = -128.5 KN-m for 1.5 (D.L+Wy).

7.5 BEAM RESULTS

There are 48 beams in each storey in the building structure, each beam given end conditions as

fixed on both the ends. In the complete building structure there are 768 beams in total.

For the simplicity in displaying the results, the beams sections whose behavior is most critical

are shown below.

From the analysis, it is found that the critical-most beam is found to be located at storey number

10 with the beam label of 22. i.e.; B22 at storey-10 is the most critical beam member of the

building structure.

Fig 7.19: Critical Beam location

0

2

4

6

8

10

12

14

16

-300 -200 -100 0 100 200

1.5 (D.L + L.L )

1.2 (D.L + L.L + Wx)

1.2 (D.L + L.L - Wx)

1.2 (D.L + L.L + Wy)

1.2 (D.L + L.L - Wy)

1.5 (D.L + Wx)

1.5 (D.L - Wx)

1.5 (D.L + Wy)

1.5 (D.L - Wy)

← Moment →

←

S

t

o

r

e

y

L

e

v

e

l

24

Fig 7.20: Dead Load

Fig 7.21: 1.2 (D.L+L.L+Wx)

25

7.6 SHEAR WALL RESULTS

There are four shear walls provided in the building structure, provided as core walls at the center

with columns at their ends acting as boundary elements. The results shown are for the two walls

located in the two different horizontal directions. The shear wall is meshed at each storey

junction, i.e.; it is meshed into 16 parts, each wall of 3.1 meters height.

FIG 7.22: Elevation of Shear Wall

26

Fig 7.23: Resultant Fmax of the Shear wall parallel to X-direction

The maximum being 675 KN and minimum -300 KN for critical wind load combination of

1.2(D.L+L.L+Wx).

27

Fig 7.24: Resultant Fmax of the Shear wall parallel to Y-direction

The maximum forces on the wall are seen at the bottom storey and decreasing as the height

increases. The maximum is -360KN.

28

CHAPTER 8

SEISMIC ANALYSIS AND DESIGN

8.1 STATIC EARTHQUAKE ANALYSIS

Seismic analyses of most of the structures are still carried out on the basis of lateral force

assumed to be equivalent to the actual (dynamic) loading. The base shear which is the total

horizontal force on the structure is calculated on the basis of structure mass and fundamental

period of vibration and corresponding mode shape. The base shear is distributed along the height

of structures in terms of lateral forces according to Code formula. This method is conservative

for low to medium height buildings with a regular conformation.

Static analysis is a type of analysis in which the building structure is subjected to loads with no

respect to time, i.e.; the loads acting on the structure are independent of time. They do not

change with time, and are the same throughout the load case.

TABLE 7.1: STATIC ANALYSIS DETAILS

CODE IS 1893:2002

SOIL Soft soil

RESPONSE REDUCTION 5 (Dual system )

SEISMIC ZONE V

IMPORTANCE FACTOR High

8.2 ELASTIC TIME-HISTORY ANALYSIS

This method has the advantage of preservation of the relative signs of response quantities of the

response histories. This is important when interaction effects are considered in design among

stress resultants. This analysis will produce the effect of higher modes of vibration and the actual

distribution of forces in the elastic range in a better way.

For the Time-History analysis of this building structure, the ground motion data chosen is of

Bhuj earthquake, January 26, 2001. The various results obtained from this analysis are chosen

such that they are the maximum of each amplitude, either positive or negative of the amplitude.

Thus we are taking the maximum envelopes for the various results.

Time →

Fig 8.1: Accelerogram of Bhuj earthquake

Ground motion v/s Time

29

Maximum amplitude = 0.699 at 43.495 sec.

Minimum amplitude = -0.782 at 34.945 sec.

The following storey shears were obtained from this method as depicted in table 7.1.

Table 7.2: STOREY SHEAR

Floor

Peak storey shear in

KN

Static Dynamic

16 1760.22 3629.33

15 3580.47 6590.95

14 5166.11 8749.57

13 6533.32 10272.46

12 7698.27 11450.51

11 8677.16 13264.32

10 9486.16 14128.56

9 10141.45 14915.79

8 10659.21 16116.58

7 11055.62 17875.9

6 11346.86 19442.2

5 11549.11 20672.09

4 11678.55 21575.28

3 11751.36 22752.51

2 11783.72 23767.23

1 11791.81 24248.6

The maximum base shear was observed from dynamic analysis. There results shown in the table

above are for the base shear in X-direction, since the building is symmetrical in plan the results

will be same for the other direction as well.

8.3 STOREY DRIFT

Storey drift is the displacement of one level relative to the other level above or below. This is

one of the most important parameter of seismic analysis to be studied. As per clause no. 7.11.1of

IS 1891:2002, the drift of any particular storey should not exceed 0.004 times the storey height.

30

TABLE 7.3: STOREY DRIFT

HEIGHT (m) LOAD X (mm) Y (mm) PERMISSIBLE

28 EQX 2.629 2.629

0.004 x 3.1 x 1000 =

12.4mm

28 Time-History 4.34 4.34

28 1.2 (D.L+L.L+EQx) 3.154 3.154

28 1.2 (D.L+L.L+THx) 5.208 5.208

28 1.5 (D.L+THx) 3.943 3.943

28 1.5 (D.L+THx) 6.509 6.509

As it can be seen from the above table, the storey with the maximum storey drift is within the

permissible limits of 12.4 mm. Hence the building structure is safe against storey drift.

CHAPTER 9

ANALYSIS AND DESIGN DETAILS

9.1 COLUMNS DETAILS

There are 32 columns in total in each storey. Amounting up to 512 columns in the complete

building structure.

In the following pages, the results for the various columns are shown, graphs plotted of:

i) Storey level v/s Axial Load.

ii) Storey level v/s Moment-X (moment acting on minor axis of column).

iii) Storey level v/s Moment-Y (moment acting on the major axis of column).

The graphs plotted are for the various prescribed load combinations suggested by

IS 1893 (Part-1):2002. The graphs plotted give us an idea about the moments acting on the

column member and helps in designing the structural member by taking the envelopes of all the

loading combinations.

Fig 9.1: Column-19

31

Fig 9.2: Axial Load v/s Storey Level

Maximum Axial Load at ground storey = 9720 KN for 1.5 (D.L+L.L).

Fig 9.3: Storey Level v/s Moment-xx

Maximum moment at top storey = -1736 KN-m for 1.5 (D.L+THx).

123456789

10111213141516

-10500-8500-6500-4500-2500-500

C-19 Storey level v/s Axial Load

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

0

2

4

6

8

10

12

14

16

-2000 -1500 -1000 -500 0 500 1000 1500 2000

C-19 Moment-X

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

32



9.1.1 DESIGN DETAILS OF COLUMN C-19

0

2

4

6

8

10

12

14

16

-2000 -1500 -1000 -500 0 500 1000 1500 2000

C-19 Moment-Y

1.5 (D.L + L.L )1.2 (D.L + L.L +EQx)1.2 (D.L + L.L +THx)1.2 (D.L + L.L -EQx)1.2 (D.L + L.L -THx)1.2 (D.L + L.L +EQy)1.2 (D.L + L.L +THy)1.2 (D.L + L.L -EQy)1.2 (D.L + L.L -THy)1.5 (D.L + EQx)1.5 (D.L + THx)1.5 (D.L - EQx)1.5 (D.L - THx)1.5 (D.L + EQy)1.5 (D.L + THy)1.5 (D.L - EQy)1.5 (D.L - THy)

37

Thus increasing the column section size to 1000x1000mm and keeping the rebar percentage the

same. The rebar percentage and various design details for the column section after increase in its

dimensions are shown below.

38

For Column section C-19 dimension of 1000x1000mm with 24 nos. of 36 diameter bars is safe

against the different load cases on it.

9.1.2 COLUMN C-18

Fig 9.5: Column C-18

39


Maximum Axial Load at ground level = -11780 for 1.5 (D.L-THx).


Maximum moment at ground storey = -950 KN-m for 1.5 (D.L+THx).

123456789

10111213141516

-12500-10500-8500-6500-4500-2500-500


1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

0

2

4

6

8

10

12

14

16

-1000 -500 0 500 1000

C-18 Moment-X

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

40

9.1.3 DESIGN DETAILS OF C-18

The design details for this column with 1000x1000mm dimensions and 24 nos of 36mm diameter

bars distributed equally on all sides.

41

Revising the section by increasing the dimensions to 1150x1150 mm and using the same rebar

distribution. The rebar percentage and various design details for the column section after increase

in its dimensions are shown below.

43



9.1.4 COLUMN C-23


Fig 9.9: Storey Level v/s Axial Load

Maximum axial load at ground storey a= 10605 KN for 1.5 (D.L+L.L).

123456789

10111213141516

-12000-10000-8000-6000-4000-20000


1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

44


Maximum moment at top storey = -1472.5 KN-m for 1.5 (D.L+THx).


Maximum moment at top storey = 1394 KN-m for 1.5 (D.L–THy).

0

2

4

6

8

10

12

14

16

-2000 -1500 -1000 -500 0 500 1000 1500

C-23 Moment-X

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

0

2

4

6

8

10

12

14

16

-1500 -1000 -500 0 500 1000 1500

C-23 Moment-Y

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

45




47

This column is not safe against the prescribed load combinations on it. Thus revising the section

by increasing its dimension to 1150x1150mm with the same rebar percentage distribution in it.

48



49

9.1.6 COLUMN C-24



Maximum Axial Load at ground storey = 10927 KN for 1.5 (D.L+THy).

0

2

4

6

8

10

12

14

16

-12000-10000-8000-6000-4000-20000


1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

50




Maximum moment at top storey -603 KN-m for 1.5 (D.L+THx)

0

2

4

6

8

10

12

14

16

-2000 -1500 -1000 -500 0 500 1000 1500 2000

C-24 Moment-X

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

0

2

4

6

8

10

12

14

16

-1500 -1000 -500 0 500 1000 1500

C-24 Moment-Y

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

51




52

Thus this column is safe for the provided section and the percentage of steel rebar distribution

provided.

53

9.1.8 COLUMN C-27


Fig 9.17: Storey Level v/s Axial Load

Maximum Axial load at ground storey = 9555 KN for 1.5 (D.L+THx).

123456789

10111213141516

-10000-8000-6000-4000-20000

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)


54


Maximum moment is at ground storey = 947.86 KN-m for 1.5 (D.L-THx).


Maximum moment at ground storey = 947 KN-m for 1.5 (D.L-THy).

0

2

4

6

8

10

12

14

16

-1500 -1000 -500 0 500 1000 1500

C-27 Moment-X

1.5 (D.L + L.L )1.2 (D.L + L.L +EQx)1.2 (D.L + L.L +THx)1.2 (D.L + L.L -EQx)1.2 (D.L + L.L -THx)1.2 (D.L + L.L +EQy)1.2 (D.L + L.L +THy)1.2 (D.L + L.L -EQy)1.2 (D.L + L.L -THy)1.5 (D.L + EQx)1.5 (D.L + THx)1.5 (D.L - EQx)1.5 (D.L - THx)1.5 (D.L + EQy)1.5 (D.L + THy)1.5 (D.L - EQy)1.5 (D.L - THy)

0

2

4

6

8

10

12

14

16

-1000 -500 0 500 1000

C-27 Moment-Y

1.5 (D.L + L.L )

1.2 (D.L + L.L +EQx)

1.2 (D.L + L.L +THx)

1.2 (D.L + L.L -EQx)

1.2 (D.L + L.L -THx)

1.2 (D.L + L.L +EQy)

1.2 (D.L + L.L +THy)

1.2 (D.L + L.L -EQy)

1.2 (D.L + L.L -THy)

1.5 (D.L + EQx)

1.5 (D.L + THx)

1.5 (D.L - EQx)

1.5 (D.L - THx)

1.5 (D.L + EQy)

1.5 (D.L + THy)

1.5 (D.L - EQy)

1.5 (D.L - THy)

55




56

Since the section is completely safe against the load combinations, revising the section by

increasing the dimensions of the column section to 1050x1050mm and with the same rebar

distribution percentage.

58



59

9.2 TIME-HISTORY ANALYSIS DETAILS

9.2.1 Pseudo Spectral Acceleration curve

The spectral acceleration curves for the building structure for different damping ratios are shown

in the graph below.

Fig 9.20: Time Period v/s PSA curve

9.2.2 Joint Displacement Curve

The joint located at the top of the building is selected and graph is plotted for its displacement

with respect to time.

Fig 9.21: Time V/s Joint Displacement Curve

60

9.2.3 Spectral Displacement Curve

The spectral displacements curve for different damping ratios are shown with respect to the time

period.

Fig 9.22: Time Period v/s Spectral Displacements curve

61

9.3 SHEAR WALL ANALYSIS AND DESIGN

9.3.1 Shear wall analysis results

Table 8.1: Design Forces in shear wall frame (X-1) under different load cases

Load Case Moment

(KN-m) Shear (KN)

Axial Force

(KN)

Axial load (KN) on

boundary elements

1.5 (D.L+L.L) 0.311 -0.15 3377.82 1799.55

1.2 (D.L+L.L+EQx) -179.996 -64.12 14593.02 7473.24

1.2 (D.L+L.L-EQx) 179.747 63.88 20104.67 10295.39

1.5 (D.L+EQx) -224.954 -80.11 18437.84 9510.78

1.5 (D.L-EQx) 224.725 79.89 24800.34 12700.01

1.2 (D.L+L.L+THx) 350.549 -118.72 32407.33 16594.75

1.2 (D.L+L.L-THx) -350.797 -133.76 33221.02 17011.39

1.5 (D.L+THx) -407.127 -148.36 40178.67 20574.22

1.5 (D.L-THx) -438.456 -167.16 41195.79 21095.02

EQ-x TH-x

Fig 9.23: Shear wall loads

62

9.3.2 SHEAR WALL DESIGN

The design of shear wall in 15-storeyed reinforced concrete building has been presented for

illustration. The design forces as per IS 1893 (Part-1): 2002 in the shear wall have already been

calculated and summarized in Table 9.1. The sectional and reinforcement details fulfilled

according to the Clauses of IS 13920:1993 are presented as under:

Clause as

per

IS 13920

9.1

9.1.1

9.1.2

9.1.3

Design requirements as

per IS 13920:1993

General Requirements

The design of shear wall is

based on the assumption that

it will be the part of the

lateral force resisting system

of the structure

In order to safeguard against

premature out-of-plane

buckling in the potential

plastic hinge region of walls,

minimum thickness of shear

wall should not be less than

150mm.

Shear wall is subjected to

combined flexure and axial

load therefore; the ends of

the wall will be subjected to

high axial load. Therefore,

it is necessary to thicken the

wall in boundary regions.

This is readily achieved by

providing flange elements

with sufficient dimensions

so as to provide of the wall

section. This effective

flange width to be used in

the design of flanged wall

sections, shall be assumed

to extend beyond the face

Details provided in the

shear walls

Lateral force resisting system in

the building is a dual system

consisting of SMRF and shear

walls. In general, the shear

walls will resist all the lateral

force being a relatively stiff

element.

Assumed thickness of shear

wall 300mm.

The shear wall is provided in

between the middle two

columns of the exterior

frames. These columns will

act as a flange element or

boundary elements of the

shear wall. Therefore, there is

no need for further thickening

of shear wall at the end or

boundary regions.

OK

OK

63

9.1.4

9.1.5

9.1.6

9.1.7

of the web for a distance

which shall be smaller of

(a) Half the distance to an

adjacent shear wall web

(b) 1/10th

of the total weight.

To control the width of

inclined cracks in the wall,

the code recommends the

reinforcement in both the

direction of walls, i.e.;

horizontal and vertical. The

minimum reinforcement

ratio should be 0.0025 of the

gross area in each direction

of the wall and should be

uniform across the cross

section of the wall.

To reduce fragmentation and

premature deterioration of

the concrete under load

reversal loading in inelastic

range, it is preferred that the

longitudinal and transverse

reinforcement should be

provided in two curtains if

(a) factored shear stress in

the wall exceeds 0.25 fck

or (b) wall thickness >

200mm.

To prevent the use of very

large diameter of

reinforcement, the code

restricts the diameter of bar

up to 1/10th

of the thickness

part.

The maximum spacing of

reinforcement in either

direction shall not exceed the

smallest of lw/5, 3tw, and

450mm; where lw is the

horizontal length of the wall,

and tw is the thickness

Calculated reinforcement in

horizontal and vertical

direction is greater than the

minimum prescribed

reinforcement. Provided

reinforcement is uniformly

distributed in both the

directions.

Since the thickness of shear

wall is 250mm and also the

factored shear stress ( v )

is greater than 0.25 fck

the reinforcement is

provided in two curtains .

(Clause 9.2.1)

Diameter of bar used in


reinforcement is 10 mm,

which is smaller than

1/10 (300) = 30 mm.

Spacing provided in


direction of reinforcement is

130mm which is smaller of

(a) lw/5 = 800 mm,

(b) 3tw=900 mm and

450 mm.

OK

OK

OK

OK

64

9.2

9.2.1

9.2.2

9.2.3

9.2.4

of the wall web. This

limitation has been

guided by the

experience and various

tests to confine the

concrete.

Shear Strength

requirements

The nominal shear

stress, v shall be

calculate as

v = Vu/tw lw

Where,

Vu =Factored shear force

tw = thickness of web

lw = effective depth of

wall section.

This may be takes as 0.8lw

for rectangular section.

The design strength of

concrete ( c) shall be

calculate as per Table-

13 of IS 456:2000

The nominal shear

stress in the wall, v

shall not exceed cmax

as per Table 14 of

IS:456:2000.

When v is less than

c, shear

reinforcement shall be

provided in accordance

with 9.1.3, 9.1.4 and

9.1.6 of the code.

Vu = 167.16 / 2 = 59 KN

tw = 300 mm

lw = 4000 mm

dw = 0.8 x 4000 = 3200 mm

The nominal shear stress,

v = mmN /1.03200300

58.83

Assume horizontal and

vertical reinforcement (As)

is 0.25% and concrete grade

M30, permissible shear

stress in concrete is

c = 0.37 N/mm2.

cmax = 3.5 N/mm2

Therefore,

v (0.1 N/mm2) <

cmax (2.8 N/mm2) .

v (0.1 N/mm2) < c (0.37

N/mm2).

OK

OK

OK

OK

65

9.2.5

9.2.6

9.3

9.3.1

Horizontal

reinforcement to be

provided as per 9.1.4

The vertical

reinforcement that is

uniformly distributed in

the wall shall not be

less than the horizontal

reinforcement in 9.2.5.

Flexural Strength

The moment of

resistance, Muv, of the

wall section shall be

calculate as for columns

subjected to combined

axial load and uni-axial

bending as per

IS:456-1978. The

moment of resistance

that is provided by

uniformly distributed

vertical reinforcement in

a slender rectangular

wall section may be

calculate as follows:

(a)For xu/lw≥x*u/lw

lwtwfck

Muv

..=

ϕ [

)]3

2168.0(2)()416.0

2

1)(1(

Lw

Xu

Lw

Xu

Minimum reinforcement =

0.25 % of Ag.

= 0.0025 x 300

= 0.75

Hence, provide 10 mm

diameter bar at 130 c/c in

2 curtains as horizontal

reinforcement.

Hence, provide 10 mm

diameter bar at 130 c/c in

2 curtains as vertical

reinforcement also.

ρ= Ast/(twlw); Ast = Aslw/Sv

ρ= Asv/twSv = 0.75/300 =

0.0025

ϕ =

30

0025.041587.0

= 0.03

λ = 400030030

3377

KN= 0.1

OK

OK

66

9.3.2

9.3.3

α1= [0.15+ϕ (1-β-

)]2

1

2

2

α2= [0.15+ϕ (1-β-

)]2

1

2

2

Ast = area of uniformly

distributed vertical

reinforcement

β= Es

fy

0035.0

87.0

= 0.516.

Es = Elastic modulus of

steel

The cracked flexural

strength of the wall

section should be

greater than its

uncracked flexural

strength.

In walls that do not

have boundary

elements, vertical

reinforcement

consisting of at least 4

bars minimum of

Lw

Xu= )

36.003.02

)1.003.0(

=0.31.

Lw

uX *=

)

1000002

41587.00035.0

0035.0(

=0.66.

Since Lw

uX *≥

Lw

Xu

α1= [0.36+ϕ (1- )]2

1

2

= [0.36+0.03x(1-0.25-0.97)]

=0.3534.

α2= [0.15+ϕ (1-β-

)]2

1

2

2

=0.02.

= [0.36+0.03x(1-0.25-0.97)]

=0.3534.

Muv = 20,780 KN-m

The remaining moment,

Mu-Muv = 3000 KN-m shall

be resisted by reinforcement

in boundary element.

Concentrated vertical

reinforcement at the edges

of the wall is more effective

in resisting bending moment

NA

NA

67

9.4

9.4.1

12 mm diameter

arranged in two layers

shall be provided along

the edge of the wall.

Boundary elements

Boundary elements are

portions along the wall

edges that are

strengthened by

longitudinal and

transverse

reinforcement. Though

they may have the same

thickness as that of the

wall web, it is

advantageous to

provide them with

greater thickness.

Where the extreme fiber

compressive stress in the

wall due to combined axial

load and bending is greater

than 0.2fck, boundary

elements shall be provided

along the vertical

boundaries of wall. The

boundary elements may be

discontinued where the

calculate compressive

stress become less than

0.15fck

.

Gross Sectional Properties

lw = 4000 mm

tw = 300 mm

Ag = twlw3

/12= 300x40003/12

=1.6 x 1012

mm4

fc = Iy

lwMu

Ag

Pu )2/(

=

12

63

106.1

10217

10001500

1010000

= 6.6 N/mm2 > 4

Therefore, providing boundary

elements.

68

9.4.2

9.4.4

9.4.5

9.4.6

A boundary element shall

have adequate axial load

carrying capacity,

assuming short column

action, so as to enable it

to carry an axial

compression equal to the

sum of factored gravity

load on it and the

additional compressive

load induced by the

seismic forc. The latter

may be calculated as

(Mu – Muv)/Cw

Where,

Mu = factored design

moment on the entire wall

section

Muv = Moment of

resistance provided by

distributed vertical

reinforcement across the

wall section.

Cw= Center to center

distance between the

boundary elements along

the two vertical edges of

the wall.

The percentage of vertical

reinforcement in the

boundary elements shall

not be less than 0.8 %

neither greater than 6%.

In order to avoid

congestion, the practical

upper limit would be 4%.

Boundary element shall

be provided as per

IS13920:1993

The adjacent columns of shear

wall act as a boundary element.

From table 9.1 the maximum

compressive axial load on

boundary element column is

Pu=16096 KN under different

loading conditions.

Let with existing column size

having dimension

750 mmx750 mm and assume

longitudinal reinforcement 2%

of the gross area.

Ag = 750x750

= 5.625 x 105 mm

2

As = 0.02x5.625x105

= 11250 mm2

Axial load capacity of

boundary element column

acting as short column

Pu= 0.4fckAg+(0.67fy-0.4fck)As

= 0.4 x 30x5.625x105 +

(0.67x415-0.4x30)x11250

= 7082.56 KN < 16096 KN

Increasing the column section

to 1200mm x1200mm

Ag=1200x1200=1.4x106 mm

2

As= 0.04x1.4x106

=20347mm2

Pu= 16765 KN > 16096 KN.

Provided vertical

reinforcement is 2% of gross

area = 20347 mm2

Provide 20 bars of 36 mm

diameter equally distributed

on the four sides of the

section.

Detailing in the adjacent

columns of shear wall of

boundary element according

to IS13920:1993.

OK

OK

OK

69

Fig 9.24: Reinforcement details in reinforced concrete shear wall

9.4 BEAM ANALYSIS AND DESIGN DETAILS

The design of one part of the block at level 8 is illustrated here.

Fig 9.25: Beam layout plan

70

9.4.1 General requirements

The flexural members shall fulfill the following general requirements.

(IS13920; Clause 6.1.2)

3.0D

b

Here 3.061.0650

400

D

b

Hence, ok.

(IS13920; Clause 6.1.3)

b ≥ 200 mm

Here b = 400 mm ≥ 200 mm.

Hence, ok.

(IS13920; Clause 6.1.4)

D ≤ 4

cL

D = 650 mm < 4

6000 mm

Hence, ok.

9.4.2 Bending Moments and Shear Forces

The end moments and end shears for six load cases (3 static and 3 dynamic) are shown in the

following tables. Since the moments and shears due to Y-direction for orthogonal beams located

parallel to X-direction show negligible shears and moments, they can be neglected from load

combinations, also applied for beams in Y-direction.

71

Fig 9.26: Beam profile

3-3 Beams

S. No. Load Case B23 B24

Left Middle Right Left Middle Right

1 1.5 (D.L+L.L) 51.748 70.6 -227.3 62 67.9 -248.2

2 1.2 (D.L+L.L+EQx) 573.3 361.846 -784.679 526.03 334.08 -754.159

3 1.2 (D.L+L.L+THx) 972.2 561.4 -1183.2 883 510.3 -1121.5

4 1.5 (D.L+EQx) 715.1 438.33 -945.14 652.9 402.03 -903.75

5 1.5 (D.L+THx) 968.35 559.67 -1180.52 880 498.52 -1118.52

Table 9.1: End moments (KN-m) for 5 critical load cases 1-1 beams



1 1.5 (D.L+L.L) 101.65 75.43 127.38 64.25 82.29 134.24

2 1.2 (D.L+L.L+EQx) 398.2 377.27 408.5 379.6 369.592 400.869

3 1.2 (D.L+L.L+THx) 538.553 538.144 589.9 494.927 505.487 557.332

4 1.5 (D.L+EQx) 454.6 427.6 462.33 432.9 417.445 452.26

5 1.5 (D.L+THx) 536.6 537 582.56 490.456 500.368 559.526

Table 9.2: End Shears (KN) for 5 critical load cases for 1-1 beams

72

Table 9.3: Percentage rebar distribution for B23

Fig 9.27: Beam Reinforcement Details for B23


Fig 9.28: Beam Reinforcement Details for B24

Rebar Percentage

Start Middle End

1.903% 0.841% 2.347%

1.960% 1.205% 1.514%

Rebar Percentage

Start Middle End

1.716% 0.707% 2.234%

1.794% 1.100% 1.367%

73

2-2 Beams



1 1.5 (D.L+L.L) -210.98 102.85 -180 45.734 69.9 -296.88

2 1.2 (D.L+L.L+EQx) 397.2 300.705 -696.88 462.052 326.355 -788.84

3 1.2 (D.L+L.L+THx) -971.71 490 -1062.7 -839.95 502.05 -1153.7

4 1.5 (D.L+EQx) 530.755 371.9 -837.92 593 394.6 -934

5 1.5 (D.L+THx) -970.51 482 -1059 -840 500 -1149.5

Table 9.5: End moments (KN-m) for 5 critical load cases 2-2 beams



1 1.5 (D.L+L.L) 140.25 84.257 168.149 101.369 123.139 207.03

2 1.2 (D.L+L.L+EQx) 402.579 353.729 371.464 403.372 390.202 434.468

3 1.2 (D.L+L.L+THx) 558.83 491.722 550.56 590.98 540.65 607.77

4 1.5 (D.L+EQx) 468 414 430.99 460 441.43 488.22

5 1.5 (D.L+THx) 560 487.78 548.3 588.67 539.62 610.467


Rebar Percentage

Start Middle End

1.959% 0.791% 2.126%

1.591% 1.043% 1.350%


Fig 9.29: Reinforcement details for B21

74

Rebar Percentage

Start Middle End

1.716% 0.615% 0.615%

1.676% 1.076% 1.076%



1-1 Beams



1 1.5 (D.L+L.L) 51.748 70.6 -227.34 62 67.96 -248.83

2 1.2 (D.L+L.L+EQx) 573.309 361.846 -784.68 526.031 334.018 -754.16

3 1.2 (D.L+L.L+THx) 972.21 561.389 -1183.2 -889.5 510.38 -1121.5

4 1.5 (D.L+EQx) 715.185 438.33 -945.14 652.98 402 -903.75

5 1.5 (D.L+THx) 969.51 560.41 -1174.5 -888.64 506.45 -1120.5

Table 9.9: End moments (KN-m) for 5 critical load cases for 3-3 beams



1 1.5 (D.L+L.L) 101.65 75.43 127.38 64.25 82.29 134.241

2 1.2 (D.L+L.L+EQx) 398.2 377.277 408.54 379.6 369.592 400.869

3 1.2 (D.L+L.L+THx) 538.553 538.144 589.989 494.92 505.48 557.332

4 1.5 (D.L+EQx) 454.59 427.5 462.33 432.93 417.445 452.26

5 1.5 (D.L+THx) 538.553 538.144 589.989 494.92 505.48 557.332


75



Rebar Percentage

Start Middle End

1.716% 0.707% 2.234%

1.797% 1.100% 1.367%



Rebar Percentage

Start Middle End

1.903% 0.841% 2.347%

1.960% 1.205% 1.514%

76

A-A beams



1 1.5 (D.L+L.L) -205.07 53.41 -203.78 -203.87 53.9 -205.07

2 1.2 (D.L+L.L+EQx) -46.958 38.222 -238.78 -238.78 59.44 -101.42

3 1.2 (D.L+L.L+THx) -250.37 81.2 -288.62 -288.62 84.19 -250.37

4 1.5 (D.L+EQx) 36.35 33.48 -267 -267.07 71.6 -86.975

5 1.5 (D.L+THx) -245 79 -290 -289 81 -246.41

Table 10.4: End moments (KN-m) for 5 critical load cases for A-A beams



1 1.5 (D.L+L.L) 133.263 107.651 184.346 130.481 110.434 171.658

2 1.2 (D.L+L.L+EQx) 209.595 158.39 204.902 204.902 160.616 209.595

3 1.2 (D.L+L.L+THx) 226.7 189.156 233.442 233.442 189.156 226.711

4 1.5 (D.L+EQx) 224.445 107.309 219.8 219.8 170.309 224.445

5 1.5 (D.L+THx) 225 190 234 234 187 225.63

Table 10.5: End Shears (KN) for 5 critical load cases for A-A beams

Rebar Percentage

Start Middle End

0.474% 0.289% 0.555%

0.289% 0.289% 0.289%



77

Rebar Percentage

Start Middle End

0.555% 0.289% 0.474%

0.289% 0.289% 0.289%



B-B beams



1 1.5 (D.L+L.L) -279.77 85.16 -110.76 -41.52 -16.24 -279.77

2 1.2 (D.L+L.L+EQx) -218.82 52.82 -94.554 -38.249 41.191 -218.82

3 1.2 (D.L+L.L+THx) -231.06 58.9 -98.4 -41.538 42.5 -231

4 1.5 (D.L+EQx) -224.08 53.671 -100.5 -41 43 -224.08

5 1.5 (D.L+THx) -230 57 -96.53 -40.47 41 -229

Table 10.8: End moments (KN-m) for 5 critical load cases B-B beams



1 1.5 (D.L+L.L) 163.2 84.08 145.17 106.91 140.422 201.485

2 1.2 (D.L+L.L+EQx) 215.579 133.263 182.113 151.527 178.333 215.759

3 1.2 (D.L+L.L+THx) 219.58 137 185.9 155.35 182.15 219.58

4 1.5 (D.L+EQx) 222.741 136.51 190.52 156.331 182.254 222.741

5 1.5 (D.L+THx) 200 136 189.65 154.74 181.98 217

Table 10.9: End Shears (KN) for 5 critical load cases for B-B beams

78

Rebar Percentage

Start Middle End

0.536% 0.289% 0.289%

0.268% 0.289% 0.289%

Table 11: Percentage rebar distribution for B15


Rebar Percentage

Start Middle End

0.289% 0.289% 0.536%

0.289% 0.289% 0.289%



79

C-C beams



1 1.5 (D.L+L.L) -232.5 85.65 -103.5 54.98 -43.7 -232.5

2 1.2 (D.L+L.L+EQx) -185.56 62.631 -83.331 38.214 -34.71 -185.56

3 1.2 (D.L+L.L+THx) -186.6 63 -83.629 38.824 -35.34 -186.6

4 1.5 (D.L+EQx) -195.5 -32.9 -87.6 37.088 -32.9 -195.5

5 1.5 (D.L+THx) -180 54 -70 29.53 -32 -184.32

Table 11.2: End moments (KN-m) for 5 critical load cases for C-C beams



1 1.5 (D.L+L.L) 129.303 52 99.7 69.19 94.4 129.303

2 1.2 (D.L+L.L+EQx) 173.9 135.767 139.972 139.972 135.767 173.908

3 1.2 (D.L+L.L+THx) 174.041 135.9 140.1 140.1 135.9 174.04

4 1.5 (D.L+EQx) 186.582 142.429 150.656 150.656 142.429 186.582

5 1.5 (D.L+THx) 170.59 127.44 140 129.46 134.42 170

Table 11.3: End Shears (KN) for 5 critical load cases for C-C beams

Rebar Percentage

Start Middle End

0.437% 0.289% 0.289%

0.218% 0.289% 0.289%



80

Rebar Percentage

Start Middle End

0.218% 0.289% 0.437%

0.218% 0.289% 0.289%



81

CHAPTER 10

CONCLUSION

The structural design of multi-storey building requires meticulous planning. Proper planning of

beams, shear wall, location and spacing of columns etc are important to maximize space usage.

While designing the various structural components it is important to note that, the sections

provided here were large in section because of the fact that the stresses and forces developed due

to the Time-History analysis are very large. Material can be saved extensively by carrying out

further optimization of various structural components. Reduction in the dimensions of sections

for the upper floors might bring down the total cost of the structure.

The effect of wind on the structure is negligible to the seismic effects on it, due to the fact that

the chosen accelerogram, i.e.; of Bhuj is a very fluctuating and strong one. Its effects on building

structures were witnessed, and they were horrible. Design data of formerly constructed buildings

subjected to seismic loading may be used to get an idea of the structural components usage and

their sizes and orientation and thus efficiently and productively provide sections. A comparative

study should be made by combination of different types of sections. This type of analysis, i.e.;

Time-History analysis is a very difficult analysis; both in executing in software as well as the

analysis runtime is quite a lot as the size of the structure increases. For this building structure the

analysis runtime was approximately 25mins. In practicality, the method of Time-History analysis

on structures used is very rare, and is applied only for very important structures. Also in

practicality, more than one accelerogram is used for Time-History analysis, depending on the

contingency. Effect of wind on building structures is more pre-dominant on taller building

structures, i.e.; 100 meters and above. Due to the fact that the building has to be in a continuous

state of lateral loading of wind, and a low probability of seismic effect, that is if this particular

building is located in a windy and high seismic zone. Also it goes without mentioning that the

sections provided for this building for the seismic dynamic analysis will be more than safe

against wind loading on it.

BEAMS:

Beams being the horizontal members are not as much affected by the seismic effects as columns

are. Nevertheless beams too require intrinsic analysis because of the moments and torsion

developing in it due to the ground motion generated because of the accelerogram.

COLUMNS:

Sections proved insufficient to transfer the load safely. So increased cross sections were analyzed

against the load combinations. Although all the revised columns sections passed the analysis

checks, it is worth noting that, the sections of the columns can be further decreased and

optimised if more columns are provided at appropriate location for the defined ground motions

induced on it.

SHEAR WALLS:

Shear walls are the most critical part of the structure acting against the lateral loading on the

building structure. Providing the wall with higher grade of concrete is of prime importance, since

82

this increases the strength of it and provided enhanced stability to the building structure. It

should also be noted that, the shear walls acting as the core wall was provided because of the fact

that this configuration was adopted from an existing structure. Efficient location of shear wall

can greatly help in reducing lateral loads on the frame structure, and better transfer of loads and

moments to the wall. Thus increasing the efficiency and use of the shear walls.

SLABS: The slab adopted for the analysis in this building structure is R.C.C slab of 150 mm thickness.

Post tensioned slabs can also be used for the building structure, furthermore it is to be noted that

the use of post-tensioned slab for this particular structure will prove more beneficial, since it

greatly reduces the loads on the beams and columns because of the lesser thickness and weight of

the slab.

83

PAPERS PUBLISHED BASED ON THIS WORK

Paper on “Multi-Dynamic Analysis and Design of a Tall Building” published in international

conference on advances in engineering and technology ICAET-2012, E.G.S Pillay College of

engineering, Tamil Nadu, India, March 2012.

REFERENCES

PUBLICATIONS AND BOOKS

‘Wind and Earthquake Resistant Building, Structural Analysis and Design’, Bungale S.

Taranath.

Seung-Eock Kim & Huu-Tai Thai for ‘Nonlinear inelastic dynamic analysis’ Engineering

Structures 32 (2010) 3845–3856.

‘Design Example of a six storey building’, by Dr. H.J.Shah and Dr. Sudhir K. Jain.

‘Structural Dynamics’ ,by Penzine and Clough.

‘Earthquake Resistant Design of Structures’ Manish Shrikande & Pankaj Agarwal.

‘Explanatory example on Indian Seismic Code IS1893 (Part-I)’, Dr. Sudhir K. Jain

‘Dynamic of Structures’, Anil k. Chopra.

Uniform Building Code (UBC) 1997, IS456:2000, IS1893:2002 (Part-1), IS 13920:1993 and

IS875:1987 (Part-3)

JOURNALS

‘Seismic Analysis of the world’s tallest building’ by Hong Fan, Q.S. Li, Alex Y Tuan and

Lihua Xu.

‘Full scale measurements of wind effects on tall buildings’, Q.S Li, J.Q Fang, A.P Jeary and

C.K. Kong.

‘Wind engineering challenges of the new generation of super tall buildings’, by Peter A.

Irwin.

complete thesis

Documents

unit volume24

nominal shear

factored shear

percentage

ritz vector

full scale

maximum base

graphs plotted