REPORT madan for check 1.pdf

8/11/2019 REPORT madan for check 1.pdf

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CHAPTER-1

INTRODUCTION


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1.1 General

The failures of mostly non-engineered buildings are mainly due to

absence of connection between infill wall and confining frames, insufficient

detailing and capacity of columns, large distance between columns and poor

quality of workmanship. Recently the uses of unreinforced masonry in RC

frames are used as an infill for the construction in India for generally all kind

of buildings. Because they are easy to construct, hence used as a basic

material for construction. And also they have to enhance the lateral stiffness

and adding to the lateral load carrying capacity of the structure.

While designing a tall building we are generally consider the weight of

infill and ignore the effects of infill on frames. But fact is that the infill reduces

the ductility of the R.C. frame and hence increases stiffness. For

determination of the stability of a frame of lateral forces the use of high

strength material and the combined action between the frame and the infill is

very important factor for us.

For in plane loading the frame members and the infill interact to

improve a collective resistance to the load. The frame is relatively flexible

whereas a panel loaded in its plane is rigid and brittle failure occurs due to

even a small displacement by cracking and subsequent disintegration. Under

favourable conditions the infill may fail explosively.

The Indian Standard code I.S. 1893 (Part 1): 2002 takes into account

the effect of infill on RC frame by increasing performance factor K of thebuilding. However the code is silent about the effect of structural geometry

and lateral deflection of the frame.

Figure 1.1 and 1.2 show a typical Infilled wall construction of a building

respectively. In this Figure Infilled wall transmit the gravity load down to the

foundation. The wall act as a bracing panels, which resist horizontal

earthquake loads. The confining elements provide restraint to masonry infill

walls and protect to the major earthquakes.


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Fig. 1.1 A typical infilled wall building (Ref. Svetlana Brzev, 2007)

Fig. 1.2 Infill wall construction in Slovenia (Svetlana Brzev, 2007)


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1.2 Objective

a) For literature survey to study the influence of infill on the behaviour

of Reinforced Concrete frames.

b) To compare story drift of frames as per I.S. code using STAAD Pro.

c) To analyse the infilled frames and their diagonal strut model for base

shear as per I.S. code.

d) To study of the infill with respect to the storey shear by equivalent

diagonal strut methods.

1.3 Literature Review

1.3.1 General

Most of the research work done to find the effect of masonry infill on

reinforced concrete. Since it has been proved through various researches

and experiments that the infills change the overall behaviour of the building

and can attract forces for by which the structure is not designed. Then

various methods of analysis and design are developed by researchers since

1940s. World map of seismic zone is shown in Figure 1.3.

Fig. 1.3 World map of seismic zone (Ref. Svetlana Brzev, 2007)


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Earlier, it was assumed that masonry infill in structural steel or

reinforced concrete frames, it can only increase the overall lateral load

capacity and therefore must continuously be valuable to seismic

performance. This concept was proved wrong when various examples of

earthquake damage were introduced due to the structural modification of the

basic frame by masonry partition and infill panels. It was proved that even if

they are comparatively weak, the masonry infill can significantly alter the

planned structural response and can attract some forces to the parts of

structure for which it has not been designed.

Fig. 1.4 Behaviour of Infilled frames (Patel 2006)

It was found that, for the dynamic response, the masonry infill wall

fillings the space between frame members not only tend to increase the

stiffness but also may completely adjust the mode of response of the frame,

changing it to a shear walls and as an effect changing the whole structure

and the resulting the distribution of forces between the different frames

constituents. Figure 1.4 shows the behaviour of Infilled frames.


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The studies of the masonry infill on the Reinforced Concrete frame can

be divided into two categories.

a) Analytical studies

b) Experimental studies

1.3.1.1 Analytical Studies

In 1967, Mallickand Severndeveloped a technique for determining the

lateral stiffness of the infilled frames. They presented a method which makesuse of the concept of finite element and is thereby able to find out the point

separation among the frame and the infill, as well as the stress distribution in

the contact intervals, as an integral part of the solution. In this method also

used slip between frame and the infill. A stiffness matrix for an element of the

infill in the state of plane-stress is obtained on the basis of assumed stress

distribution, together with consisted load matrixes for the kinds of loads

experienced by an infilled frame. The method deals with rectangular, as wellas square, laterally loaded infilled frames.

Smith andCarter(1969) observed the behaviour of multi-storey infilled

frames for the case of lateral loading. It shows that the effect of the infilling of

the frame, relative to the same non-infilled frame subjected to similar forces

is to reduce substantially the bending moments in the member. On the basis

of results, Smith established the design based on equivalent diagonal strut

concept and assumed all the joints of the frame as pin jointed.

Liaw and Kwan (1984) developed a method of plastic design for both

integral and non-integral infilled frames. They proposed a unified plastic

theory for both the frames on the basis of non-linear behaviour of infill

frames. They also took into account the formation of plastic hinge in the

frame, shearing of interface connection and cracking and crushing of the

infilled panel. They developed the plastic method of design and construct

design charts for rapid computation. In 1990, they introduced a paper in


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which six large scale models of 2 bays, multi-storeyed frames of steel work

frame and concrete infill construction were tested. This experiment set to be

a milestone for development of a general plastic theory for multi-bay infilled

frames. They introduced the plastic method for rapid computation of design

and prepared design charts.

Achyuntaet al. (1994) established a procedure for the inelastic analysis

of infilled panels using the equivalent concept of diagonal strut and piecewise

linear finite element analysis. While they tested in laboratory found that w/d

ratio varying and equal to a constant value of 0.2 compare will within the

experimental results.

Asteris (2002) presented a paper for the analysis of brickwork infilled

plane with a new finite element method for lateral force. In this study he

considered the infilled finite element model. In this model the two corners

were linked at the end of the compressed diagonal of infilled. He tested for

the acceptance of the derived deformation mesh. For the purpose of study he

took one-storey one-bay infilled frame for seismic analysis. The section of the

frame was constructed with reinforced concrete 30/40 cm for both beams and

columns. He studied a computer program for a 2-D linear elastic analysis

under static load of the infilld plan frames.

Patel (2012) studied an existing RC frame building four storeys with

open ground floor with the help of the software SAP2000NL. For the study he

considered a two type of models with and without infill wall. He assumed that

the infills behave as diagonal strut. The dimensioning of infill wall was done

with the help of the method given by Smith and Carter (1969). He performed

a pushover analysis.

Sabriet al. (2013) studied a pushover analysis with the help of ZeusNL

software by using infill as equivalent diagonal strut. When subjected to

equivalent static load, with the help of obtained result they showed that infill

wall has considerable effect on the lateral stiffness and resistance ofreinforced concrete. Also they found that infill enhances seismic


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performance. They used three type of model for analysis of building frame

bare frame, partially infilled and completely infilled. According to him infill has

always beneficial to us in comparison to other models.

Riveoet al. presented a nonlinear dynamic model of infilled frame for the

study of the interaction between wall and frame. In this they studied the

nonlinearities of the model i.e. the interaction between wall and frame, the

discontinuities between frame and wall, frame inelastic behaviour, failure and

cracking of wall and bracing effect of wall on the frame. They studied on

three-storey, one bay frame infill with walls. The model was analysed using a

computer program AWALL. In this analysis, finite element method was

considered.

1.3.1.2 Experimental Studies

Kashifet al. (2010) studied that the seismic behaviour of RC frames with

brick masonry infill for various parametric changes to observe their influence

in deformation pattern of the frame. They also found that the effect of softstorey on frame structure due to horizontal loading. For this study a linear

finite element analysis had been performed with the help of ANSYS software

package or predicting the inelastic behaviour of RC high rise frame with brick

masonry infill. The objective of their study was to find out the effect of

horizontal loading on reinforced concrete frame with masonry infill for with

and without soft storey effect. In this study for different properties of beams

and columns the comparisons of a 10 storey 3 bay building had used.

Zhang et al. (2011) present advantage and disadvantage using three

mechanical models of infill walls in a RC frame. They studied on three

analytical models of the infill walls and some conclusions were obtained that

RC frame carries more inertia force it is due to increase in the stiffness to the

RC frame. For nonlinear dynamic analysis of reinforced concrete frame of

with and without infill walls they are using CANNY software. They showed

that the failure modes are like as the failure pattern of seismic. That provedthat the change failures of the frame are mainly due the presence of infill


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walls. Hence, infill walls are considered in the seismic design of the multi-

storeyed RC frame.

Ahmedet al. (2013) contributes on the basis of effect of cyclic load an

experimental study for the behaviour and ductility of H.S.R.C (High Strength

Reinforced Concrete) frames with infill wall. On the basis of results obtained

they showed that the lateral load resistance for infilled frame was greater

than bare frame and also the ductility was less than bare frame.

Hirde and Bhoite (2013) studied a nonlinear analysis on 8 storey RC

moment resisting frame of three models by using SAP 2000 software

package. Model A is bare frame, model B is infill excluding ground story so

as to make it as soft story and model C is masonry infill throughout the height

of the building. The pushover analysis is carried out for the analysis. They

showed that the performance level of the bare frame and open ground soft

story roof displacement for bare frame is greater than frame with masonry

infill and open ground soft story. They also showed that the performance is

modified after modelling of infill walls with comparison to bare frame. In the

case of masonry infill the plastic deformation is within limit of columns and

beams of masonry infill. They showed that the masonry infilled add significant

lateral stiffness, overall ductility, strength and energy dissipation capability.

Adukadukam and Sengupta (2013) studied on seismic analysis of a

framed building with infill walls on frame models. They showed that the

equivalent strut method is suitable for modelling the walls in a large building.

They developed the nonlinear axial load versus deformation relationship on

the basis of experimental data. Also the parabolic-plastic relationship is

idealised as a tri-linear axial hinge property was developed using commercial

software SAP 2000 NL for the pushover analysis of two framed reinforced

concrete buildings.


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Many researchers proved that the presence of infill wall influence the

behaviour of seismic load of structure. Analytically the model of infill frame

are divided into two parts

a) Macro Modelling and

b) Micro Modelling

The macro model deals with equivalent diagonal strut method while,

micro model deals with finite element method. The effect of infill on frame are

studied on several models, as a single strut model three strut model and

finite element model. Many researchers presented the equivalent diagonal

strut model which is given in Figure 1.5.

Fig. 1.5Equivalent strut width (Samoila 2012)


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1.4 Indian code Recommendations

I.S. 1893 (Part 1): 2002 Criteria for earthquake resistant design of

structures includes the effect of infill by increasing the performance factor K

which actually increases the base shear of the structure. This characteristic is

being studied in this thesis.

1.5 Overview of the Dissertation

Chapter 1 is Introduction and Literature Review of the work which give

the definition of Infill wall and the brief summary of the available literature on

various methods of design and experiments on Infill frame.

Chapter 2 is Analysis of the work which gives the brief summary about

the proposed work

Chapter 3 lateral load analysis of Infilled frame discuss the methods

given in IS 1893 (Part 1) 2002, modelling of infilled frame as diagonal strut

frame strength of infill material.

Chapter 4 numerical study and discussion frames of different storey

solved for base shear by Seismic coefficient method. The deflections of the

entire frame were studied and the strength of infill is worked out.

Chapter 5 gives the conclusions.

Annexure A shows the seismic zone map of India.

Annexure B discusses the concepts used by STAAD Pro to analysis of

the frames.


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CHAPTER 2

METHODOLOGY


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2.1 General

The methodology adopted was to determine the response of multi-

storeyed buildings under the action of seismic loads. The methodology

adopted is listed below:

1) A five storey frame building was adopted for investigate the response

under seismic action.

2) The frame buildings was analysed first without the consideration of

effect of infill i.e. bare frame. the effect of infill systems were

considered as

a) soft storey frame i.e. partially infilled frame

b) Uniformly infilled frame.

3) For modelling and analysis STAAD Pro. Software was used. The

buildings were modelled as 3-D frame skeleton.

4) The response quantities lateral displacement, axial force and storey

drift were obtained from the analysis for the bare frame and infilled

frames systems.

5) Based on the comparison of the response quantities, the

effectiveness of a bracing system was assessed.

2.2 Design of Infilled Frame System

The type of structural system chosen for this investigation was the

common type of bare frame (Fig. 2.1), soft storey frame (Fig. 2.2) and

uniformly infilled (Fig. 2.3) frame systems.

It was also decided that we should study the behaviour of diagonal

tensions and compressions separately. The effect of infill was considered for

exterior walls of reinforced concrete bare frame.


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Fig. 2.1 Bare frame Fig. 2.2 Soft Storey frame


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Fig. 2.3 Uniformly infilled Frame

2.3 Problem Statement

For seismic analysis of reinforced concrete buildings with different types

of frame system, the methodology considered in this dissertation was to

compare the seismic performance of buildings in terms of lateraldisplacement, storey drift and axial force.

Various constants and dimensions are listed below as follows:

Type of structure: - Multi-storey rigid jointed frame (special RC moment

resisting frame)

Seismic Zone: - IV (Table 2, IS 1893 (Part 1): 2002)


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Number of stories: - Five (G+4)

Material Properties

Modulus of Elasticity of concrete (Ec) = 130 kN/m2

Modulus of Elasticity of infill (Ei) = 6.3106kN/m2

Size of Column = 350 mm 350 mm

Size of beam = 350 mm 350 mm

Floor height = 3 m

Specific Weight of Concrete = 25 kN/m2

Specific Weight of Infill = 19 kN/m2

Thickness of Infill wall = 230 mm

Second Moment Of Inertia = 3.5710-3mm4

Seismic Properties

Importance factor (I) = 1

Earthquake Zone = IV

Earthquake Zone factor = 0.24

Damping Ratio = 5%


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CHAPTER-3

MODELLING OF INFILLED FRAMES


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3.1 General

Masonry infills are used as interior dividing wall and as exterior walls to

form a part of the building in multi-storey buildings. In general practice of

India, while analysing the building frame we ignore that the strength and

stiffness of infill. But in actual, infill walls increase extensively to the strength

and stiffness of the structures and hence their negligence cause failure of

masonry as well as multi storey building.

The failure is basically due to stiffening effect of infill panels which is

cause of

a) unequal distribution of lateral forces in the different frames and

overstressing of some of the buildings frames,

b) soft storey or weak storey, and

c) short columns effect

3.2 Classification of Infill wall

FEMA 306 (1998) and Eurocode 6 (1996) define the classification of

Infill Masonry Wall. Eurocode 6 classified masonry infill wall into three groups

like Unreinforced Masonry, Confined Masonry and Reinforced Masonry.

FEMA 306 also classifies these into three categories like Reinforced

Masonry, Unreinforced Masonry and Infilled Masonry. From both there are

difference between confined masonry and infilled wall which in terms of

approaches of construction and lateral resistance mechanism.

The variations of stiffness and strength are dependent on the

mechanical properties of the material used for the infill e.g. masonry concrete

blocks reinforced concrete etc. the extension of the infill in the frame has also

affect the interaction between the frame and the infill wall.


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3.2.1 Types of Infill Wall

In this dissertation three types of frame structure are considered for the

analysis by STAAD Pro. software in seismic zone IV from IS code 1893(Part-

1): 2002.

a) Bare frame

b) Soft storey frame

c) Uniformly Infilled frame

Fig. 3.1 shows the three dimensional view of bare frame, Fig. 3.2 shows

for soft storey frame and Fig. 3.3 shows for uniformly distributed frame

respectively.

Fig.3.1 3-D rendering view of Bare frame Fig.3.2 3-D rendering view of

Partially Infilled frame


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Fig. 3.3 3-D Rendering view of Uniformly Infilled frame

3.3 Modelling of Infill wall

Most of the research work had done to find the effect of masonry infill

on reinforced concrete frames was for static loading. The investigators have

applied cyclic static loading to produce the effect of earthquake or wind

forces. The literature survey also relates the most of the new researches are

based on diagonal strut method. In FEMA 356 (2000) presented a method, in

which, this is based on nonlinear finite element analysis of a composite frame

with infill walls. The equivalent diagonal strut has same thickness and

modulus of elasticity as the infill wall which is shown in Fig. 3.4. For finding

the width of equivalent diagonal strut the expression given in FEMA 356

clause 7.5.2.1 (equation 7-14) has been used.


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The equivalent width of diagonal compression strut a is

a = 0.175 (1 hcol)-0.4 rinf (2.1)

Where,

1 = [(Eme tinf sin2) / 4 Efe Icol hinf] . (2.2)

hco l = Column height between storey, in m.

hinf = Height of infill panel, in m.

Efe = Modulus of elasticity of frame, in kN/m2.

Eme = modulus of elasticity of infill material, in kN/m2.

Icol = Moment of inertia of column, in m4.

Linf = Length of infill panels, in m.

rinf = Diagonal length of infill section, in m.

tinf = Thickness of infill panel and equivalent diagonal strut, in m.

= Angle whose tangent is the infill height-to-length aspect ratio,

in radians.

1= Coefficient which are used to determine equivalent width of infill

strut


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Fig.3.4 Compression Strut Analogy-Concentric Struts (FEMA 356)

3.4 Indian Code Recommendations for infilled Frame

Indian standard code IS 1893 (Part-1): 2002,Criteria for earthquakeresistant design of structures studies the structure by two different methods.

First is Seismic Coefficient Method and other is Response Spectrum Method.

In both the methods, it describes the effect of infill through performance

factor. This performance factor (K) is increased for infilled frames which

directly increase the base shear of the structure, which in turns means that

the structure is inviting more earthquake forces for infilled frames.

The main objective of performance based seismic design was to avoid

total disastrous loss and it is to resist the structural damages caused. For this

purpose equivalent lateral force method is used to calculate real strength of

the structure.

For new ordinary structure following are the two-level performance are

a) Under DBE, damage must be restricted to slight structural damage

in order to enable immediate occupancy after DBE.


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b) Under MCE, damage must be limited to moderate structural

damage in order to ensure life safety after MCE.

Fig. 3.5 shows the plan of the frame considering for analysis. Fig. 3.6

shows the elevation of the uniformly infilled frame, Fig 3.7 shows the

elevation of soft storey frame respectively.

Fig. 3.5 Plan of the G+4 building


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Fig. 3.6 Elevation of G+4 Uniformly Infilled frame building

Fig. 3.7 Elevation of Soft Storey Infilled frame


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3.5.1 Strength of Infill Frame

The presence of infill is the cause of (i) unequal lateral forces in the

different frames of a building; (ii) vertical irregularities in strength and

stiffness; (iii) horizontal irregularities; (iv) the effect of short column in infilled

frame and (v) failure of masonry infills-out-of-plane and in-plane failures.

The brick infill may be fail by

1) Sliding shear failure of the masonry along horizontal mortar

arrangements.

2) Cracking alongside the compressive diagonal and then by crushing

near one of the loaded corner or by crushing only.

3.5.2 Seismic Analysis of Infilled Frames

While using IS code 1893 (Part 1): 2002 we find the member forces in

structure for seismic loading. For designing a structure seismic coefficient is

very important factor and it is reliant on various variables factors and hence

for each case of designing it is very difficult to determine the exact value of

seismic coefficient. The I.S. code has divided country into only four zones

while earlier revision divided into five divisions. The value of seismic zone

factor has been modified; hence these reflect more realistic values of

Maximum Considered Earthquake (MCE) and for each case the service life

of structure in seismic zone. Designers expect more earthquake shocks of

less or more intensity in future. The seismic zoning map of India is given inFigure A.1

3.5 Load Combination

The structure has been analysed for different load combinations

including the entire previous load in proper ratio as per I.S.1893 (Part 1):

2002 (clause 6.3.1.2) for limit state design of concrete buildings.


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CHAPTER-4

NUMERICAL STUDY


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4.1 General

In the present work, a five storey Reinforced concrete frame building

situated in seismic zone IV, is taken for study purpose. The plan area of the

building is 99 m. It consists of 3 bays@ 3 m in each in Z-direction. Height of

the building is 15 m, 5 bays@3 m. Building is symmetrical about both the

axes. The building consists of special moment resisting frame. The plan and

elevation of the building are shown in Fig. 3.4 and Fig. 3.5 respectively. For

analysis work, it was assumed that the effect of soil interaction was

neglected. The columns were assumed to be fixed at ground level.

With the help of I.S. 1893 (Part 1): 2002 method and by diagonal strut

method three structure of G+4 building of different type of frames has been

considered. Frame first is simply bare frame, second is open ground storey

i.e. soft storey and last one is uniformly distributed infill throughout the frame.

We study the effect of infill on building frame by these and compare between

them. Then these cases with simple infill and equivalent diagonal strut

method were solved with the help of Seismic Coefficient Method.

4.2 Important Definitions

I.S. code 1893 (Part 1):- 2002 (Fifth Revision) states some important

terms which are:-

a) Critical Damping: - The damping further than which the free vibration

motion will not be oscillatory.

b) Damping: - It is defined as the capability of the structure to disintegrate

the energy of the earthquake ground shaking. It is due to effect of

imperfect elasticity of material, internal friction, sliding, slipping, etc. In

reducing the amplitude of vibration. It is generally expressed as a

percentage of critical damping.


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c) Importance Factor (I): - It is a factor used to determine the design

seismic force which depends on the functional use of the structure,

characterised by dangerous concerns of its failure, economic

importance, its post-earthquake functional need, or historic value.

d) Response reduction factor (R):- It is the factor by which the actual

base shears forces that would be generated if the structure were to

remain elastic during its response to the Design Basis Earthquake

(DBE) shaking, shall be reduced to obtain the design lateral force.

e) Ductility: - It is defined as the capacity of the building materials,

structure or its members to absorb energy for large inelastic

deformations without significant loss of strength and hence also

stiffness. It is one of the most important factor which affect the

earthquake.

f) Design Basis Earthquake (DBE): - During design life of building frame

structure earthquake occurs at least one time.

g) Maximum Considered Earthquake (MCE):- The most severe

earthquake effects considered by this standard.

h) Natural Period (T):- Natural period is time period of undamped free

vibration of the structure.

i) Seismic Weight (W):- Seismic Weight is the sum of total dead load

and appropriate amount of considered imposed load.

j) Zone Factor (Z):- It is a factor to find the design spectrum for structure

which depends on the witnessed maximum seismic risk considered by

Maximum Considered Earthquake (MCE) in the earthquake zone. The


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basic zone factors involved for the evaluation of effective peak ground

acceleration.

k) Storey Drift: - Storey drift is the relative displacement of one level with

respect to the other level above or below of frame building.

l) Design seismic base shear (VB):- It is the total design lateral force at

the base of a structure.

From Figure A.1, the basic zone factor (Z) of different zone has beengiven as in table 4.1

Table 4.1: Seismic zone factor of India

4.3 Equivalent Lateral Force Methods

The total design lateral load or design base shear alongside anyprincipal direction shall be determined by the expression

VB = Ah W .... (4.1)

where,

Ah = Design horizontal Acceleration seismic coefficient for

a structure.

W = Seismic weight of building.

Zone Zone Intensity Seismic Intensity

II 0.10 Low

III 0.16 Moderate

IV 0.24 Severe

V 0.36 Very Severe


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The value of Ahshall be determined from the expression given as

Ah= ()(

) (

) .... (4.2)

where,

Z = zone factor given in table 1

I= Importance factor,

R = Response reduction factor

Sa/g= Average response acceleration coefficient for rock

and soil site from IS 1893(Part 1): 2002

For medium soil sites,

Sa/g = 1+15T, 0.00 < T < 0.10 ........ (4.3)

= 2.50 0.10 < T < 0.55

= 1.36/T 0.55 < T < 4.

According to I.S. 1893 (Part 1): 2002 the distribution of lateral load along

height of the building as per the expression

Qi = Wi hi2 / I hi

2 .....(4.4)

where,

Qi= Design lateral force at ithfloor

Wi= Seismic weight of floor i

hi= Height of the floor I measured from base, and


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n = Number of stories in the building

The I.S. code recommends that T maybe determined as follows formulti-storied buildings.

For a moment resisting frame building without brick infill panels Natural

Period (T) can be calculated by the following expression

T = 0.075 h0.75 for RC frame building. ........ (4.5(a))

= 0.085 h0.75 for steel frame building. .... (4.5(b))

where,

h = height of the building, in m.

For all other buildings, including moment-resisting frame buildings with

brick infill panels

T = 0.09h/d .... (4.6)

where,

h = height of building, in m.

d = base dimension of the building along the direction of

lateral load at the plinth level, in m.

4.4 Load Calculation

As per IS: 875, the following loads are considered for the analysis of

the building frame.

4.4.1 Self-Weight of the Building Frame

The self-weight of the frame is taken as one which is acting in minus

Y-direction.


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4.4.2 Slab Weight

The weight of the slab which is acting as dead load is calculated.

Load due to slab = slab thickness unit weight of reinforced cement concrete

Load due to slab = 0.150(slab thickness) 25(unit weight of RCC)

= 3.75 kN/m2

4.5 Dead Load Considerations

The dead loads which are considered to be acting on the frame

1. Floor finishes = 1 kN/m2

2. Unknown panels = 0.5 kN/m2

4.5.1 Total dead load due to slab

The total dead load is the sum of the different dead loads acting on the

frame.

Total dead load = self-weight of the building frame + slab weight + dead load

considerations.

Total dead load = 3.75+1.5

=5.25kN/m2

4.5.2 Dead load due to Infill wall

Uniformly distributed load on beams to 230 mm wall

= (height of the wall) (wall thickness) (unit weight of the masonry)

= (3-0.3) (0.23) (19)

= 11.8kN/m

4.5.3 Dead load due to parapet wall

UDL from parapet wall of 115 mm thick and 0.9 m height

= 0.1150.919

=1.97kN/m


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4.6 Live Load

Live load is considered as per I.S. code I.S.:875(Part II)-1983 for a

residential building is taking as 3 kN/m2.

4.7 Seismic load

4.7.1 Design Lateral Forces

For the determination of lateral force in the code are based on the

approximation effects, yielding can be accounted for linear analysis of thebuilding considering the design spectrum.

The design horizontal seismic coefficient (Ah) for structure will be

determined as per I.S. 1893(Part 1):2002, by the expression

Ah= (Z/2) (I/R) (Sa/g)

4.7.2 Seismic Weight

The seismic weight of each floor is its full dead load. While computing

the seismic weight of each floor, the weight of columns and walls in a storey

shall be equally distributed to the floors above and below the storey. The

seismic weight of all building is the sum of the seismic weight of all the floors.

4.7.3 Seismic Weight Calculation

Seismic weight due to beam = 0.35 0.35 3 25 24 = 220.5 kN

total weight due to slab = 0.150 9 9 25 = 303.75 kN

total seismic weight of column = 9 4 0.23 3 19 = kN

live load = 9 9 0.75 3 = 182.25 kN


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Page | 34

Total seismic weight of frame calculated from STAAD Pro. V8i package

= 6512.67 kN

4.8 Calculation of Base Shear

The total design lateral load or design base shear along any principal

direction is,

VB = Ah W

Time period T is

T = 0.09 h / d

= 0.09 15 / 91/2

= 0.45

hence, Sa / g = 2.379 [from, Code IS 1893(Part 1): 2002]

Ah=024 / 2 1 / 5 2.5

= 0.0571

Base shear VB= 0.06 6512.67

= 371.860 kN in each direction

Table 4.2: Base shear calculation for different type of frames

Frame Seismic weight

(kN)

Ah VB (kN)

Bare frame 6512.67 0.0571 371.860

Soft storey frame 6987.22 0.0571 398.956

Uniformly infilled

frame

7105.85 0.0571 405.730


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Page | 35

From table 4.2, it was observed that for different load condition of

frame structure the base shear of Uniformly Infilled frame (VB = 405.730 kN)

is more than that of other type of frame structures.

4.8.1 Calculation of Storey Shear

Vertical storey shear distribution for the whole building can be

determined using the following expression

Qi=VB [Wi hi2 / i hi

2]

Due to symmetry lateral force in z-dir. is same as that of x-direction. The

designed lateral force at different storey level is calculated for bare frame

structure.

Table 4.3: -Design lateral forces at each floor for Bare Frame.

Floor level Height

(m)

Seismic forces

Lateral force(kN) Storey shear(kN)

Fx Fz Fx Fz

5 15 165.733 165.733 165.733 165.733

4 12 109.934 109.934 275.667 275.667

3 9 61.838 61.838 337.505 337.505

2 6 27.484 27.484 364.989 364.989

1 3 6.871 6.871 371.86 371.86


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4.9 Calculation of Equivalent Diagonal Strut

From equation 3.1, equivalent width of diagonal strut is

a = 0.175 (1 hcol)-0.4 rinf

Where,

hcol = Column height between storey, in m = 3 m

hinf = Height of infill panel, in m = 3.0-0.35 = 2.65

Efe = modulus of elasticity of frame, kN/m2 = 3.2 107kN/m2

Eme = modulus of elasticity of infill material, kN/m2= 6.3 106kN/m2

Icol = Moment of inertia of column, in m4 = 1.387 10-4m4

Linf = Length of infill panels, m

rinf = Diagonal length of infill panel, m = (32 + 32) = 4.24m

tinf = Thickness of infill panel and equivalent strut, m.

= Angle whose tangent is the infill height-to-length aspect ratio,

= 45= /4

1 = Coefficient used to determine equivalent width of infill strut

1= ((Eme tinf sin2) / 4Efe Icol hinf)1/4

= [(6.31060.23sin (/2)) / (43.21071031.38710-33.65)]1/4

= 1.329

a= 0.175 (1.3293)-0.44.24

= 0.43 m


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Hence,

Cross-section of equivalent diagonal strut

= 0.43m0.23m

Hence, for analysis the cross-sectional dimension of equivalent

diagonal strut has been used as 0.43m0.23m.

STAAD Pro. is used to calculate the displacement, storey drift, base

shear, lateral load for preparing charts and tables for x-direction of loading.

After calculating from STAAD-Pro V8i, we have

Table 4.4: Joint Displacement (mm) at floor level of G+4 building for seismic zone IV

for x-direction

FLOOR

LEVEL

FLOOR

HEIGHT

(m)

FRAME

BARE

FRAME

(mm)

SOFT

STOREY

(mm)

UNIFORMLLY

INFILLED

(mm)

1 3 4.782 3.411 1.23

2 611.517 7.365 2.853

3 917.948 11.055 4.416

4 1223.239 13.908 5.736

5 1526.589 15.891 6.693

Lateral displacement vs. storey level of different frames in G+4

building. From Table 4.4 the maximum displacement of bare frame is 26.589

mm, soft storey frame is 15.891 mm and uniformly infilled frame is 6.693 mm.

the result shows that the minimum displacement in uniformly distributed

frame with compare with other types of frames.


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Page | 38

Fig.4.1: Graph between joint displacement and floor level for Bare Frame, Soft

Storey and Uniformly Infilled Frame.

Fig. 4.2 shows the isometric view of displacement of bare frame, Fig.

4.3 soft storey frame and Fig. 4.4 uniformly infilled frame respectively.

0

1

2

3

4

5

6

0 5 10 15 20 25 30

Floorlevel

Joint Displacement (mm)

Graph between Joint Displacement and Floor level

BARE FRAME

SOFT STOREY

UNIFIRMLY INFILLED


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Page | 39

Fig.4.2 Isometric view of displacement of bare frame

Fig. 4.3 Isometric view of displacement of soft storey frame


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Page | 40

Fig.4.4 Isometric view of displacement of uniformly infilled frame

Table 4.5: Lateral Load (kN) of G+4 Building for Seismic Zone IV

FLOOR

LEVEL

FLOOR

HEIGHT

(m)

FRAME

BARE

FRAME

(kN)

SOFT

STOREY

(kN)

UNIFORMLLY

INFILLED

(kN)

1 3 5.371 6.959 7.396

2 6 21.486 28.312 29.582

3 9 48.343 60.421 66.56

4 12 85.943 109.246 118.329

5 15 128.26 160.542 170.28


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Page | 41

Fig. 4.5 Graph between Lateral Loads vs. Floor Level for Bare frame, Soft storey

frame and Uniformly Infilled frame

Table 4.6: Storeys Drift of G+4 Building for Seismic Zone IV

FLOORLEVEL

FLOORHEIGHT

(m)

FRAME

BARE FRAME SOFT

STOREY

UNIFORMLLY

INFILLED

1 3 0.0016 0.0014 0.0004

2 6 0.0025 0.0013 0.0005

3 90.0021 0.0012 0.0005

4 12 0.0018 0.0010 0.0004

5 15 0.0012 0.0007 0.0003

0

1

2

3

4

5

6

0 50 100 150 200

FLO

OR

LEVEL

LATERAL LOAD (kN)

LATERAL LOAD vs FLOOR LEVEL

BARE FRAME

SOFT STOREY

UNIFIRMLY INFILLED


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Page | 42

Fig. 4.6 Graph between storeys drifts and floor level for Bare frame, soft storey

frame and uniformly infilled frame

0

1

2

3

4

5

6

0 0.0005 0.001 0.0015 0.002 0.0025 0.003

FLOOR

LEVEL

STOREY DRIFT

STOREY DRIFT vs FLOOR LEVEL

BARE FRAME

SOFT STOREYUNIFIRMLY INFILLED


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Page | 43

CHAPTER-5

RESULTS AND DISCUSSIONS


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Page | 44

5.1 General

In this dissertation the seismic analysis of different frames inreinforced concrete buildings was worked out with the help of STAAD Pro.

software in seismic zone IV. The result was considered in terms of lateral

displacement, storey drift, and axial force. The result was compared with

different types of frames and observed that the uniformly infilled frame was

the most efficient and effective in reducing the seismic demands of lateral

displacement, storey drift.

5.2 Lateral displacement

From Table: - 4.4, the results are compared between the bare frame

and various types of RC frames. It is observed that the maximum

displacement of bare frame is more than the soft storey or uniformly infilled

frame.

While comparison between different types of RC frame, it is find out the

Uniformly Infilled Confined masonry frame reduce more lateral displacement.

5.3 Storey drift

From Fig. 4.6, it is observed that the storey drift of bare frame is more

as compared to Infilled Frame. While comparing the different types of frame

systems, it is found that infilled frame systems reduce more storey drifts with

respect to other types of frame systems.

5.4 Comparison of Results for Displacement

The maximum lateral displacements are obtained in X direction with the

help of STAAD Pro.V8i Software Package. The results show that Uniformly

Infilled Frame reduced more lateral displacement with comparison to other

type of frame. The variation of maximum displacement and percentage

reduction of different type of model are presented in table 5.1


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Page | 45

Table 5.1 Comparison between frames for % reduction of displacement

No of Storeys Bare frame Uniformly infilled

frame

% reduction

5 26.589 6.693 74.82%

5.4.1 The maximum displacements (mm) in X-direction of different

Frames

The Uniformly Infilled Frame Model reduces the maximum percentage

reduction (71%). So, Uniformly Infilled frame Model is very effective with

comparison to bare frame and soft storey frame.


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Page | 46


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Page | 47

6.1 Conclusion

Following conclusion is made from the present study of analysis results

under consideration of earthquake effect:-

1) Because of the increase in stiffness, the equivalent model frame of

uniformly infilled frame shows lesser displacement in comparison to

soft storey frame of building.

2) Joint displacements are very much reduced in diagonal strut model of

uniformly infilled frame as compared to both bare frame and soft

storey frame, because increase in stiffness of the modelled frame.

3) For five storey building frame, the base shear is almost same for

bare frame and uniformly infilled frame and soft storey frame model.

4) The values of axial loads to cause crushing of infill and the axial load

to cause shear failure. For the present study the frames are strong

enough to carry the loads.

5) All the values are satisfying the inter storey drift criteria, which is

prescribed by IS 1893 (Part 1): 2002, that the maximum horizontal

relative displacement due to Earthquakes forces should not exceed

0.004 times the difference in level between the forces.

6.2 Future Recommendations

Within limited scope of the present work, the broad conclusions drawn

from its work have been reported. However, further study can be undertaken

in the following areas:-1) In the present study, the equivalent lateral force method had been

carried out for five storey frame buildings. This study can further be

extended for tall buildings.

2) In the present study, analysis is done with the help of STAAD Pro

software. Work can be done to optimize the sizes of various frame

elements.

3) A comparative study can be done to see the effect of infill wall onperformance based seismic design.


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Page | 48

ANNEXTURE A

Fig. A.1 India seismic zone map (source, IS 1893 (Part 1): 2002)


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Page | 49

ANNEXTURE B

ABOUT STAAD Pro

The Equivalent Force analysis is done with the help of Computer

Software (STAAD Pro V8i Package). This software system is based on

stiffness matrix analysis. The analysis of the structure requires the solution of

large number of linear algebraic system. The problem can be handled in a

systematic way in matrix notation. The structure is idealised into a skeletal

system which retains the properties of the original structure. The stiffnessmatrix of the structure as a whole is assembled from the stiffness of the

individual members. The resulting equation can then be solved for either

force or displacement components in dynamic analysis.

The stiffness matrix method of analysis is the one in which

compatibility of displacement is assumed and the equilibrium equations at the

modes are formulated in terms of the nodal displacement components. The

method proceeds from part to whole i.e. member stiffness matrix are

generated and contribute to the assembly of the overall stiffness matrix are

generated and contributed to the assembly of the overall stiffness of the

structure. The stiffness matrix of a rigid frame member arbitrarily oriented in

2D plane with three degrees of the freedom at each end can be derived by

imposing a unit displacement along each degree of freedom and computing

the induced forces corresponding to all other degree of freedom.

The arbitrarily orientation of rigid frame meeting at a node makes it

difficult to set up equilibrium equations at nodes in terms of nodal

displacement. For this transformation force components from member or

local coordinates system to the global co-ordinate system is achieved by

originally derived in local coordinate system and this needs to be modified so

to represent the stiffness matrix in global co-ordinate system.


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Page | 50

REFERENCES

1. Achyuntha et al., (1994). Inelastic behaviour Of Brick infilled

reinforced Concrete frames. J. Of Struct. Engg. 21, July, pp. 107-115.

2. Agarwal, P. and Shrikhande, M. (2006), Earthquake Resistant Design

of Structures, PHI Learning Ltd, New Delhi, pp.100-156.

3. Asteris, P. G. (2002), A New Method of Analysis for masonry Infilled

frames. SEWC 2002, Yokohama, Japan. pp. 1-8.

4. Attajkani, S., Khamlichi, A., and Jabbouri, A. (2013). Modelling the

Effect of Infill Walls on Seismic Performance of Reinforced Concrete

Buildings. IJJERA ISSN: 2248-9622 Vol. 3, Issue 1, January-

February 2013, pp.1178-1183.

5. Bezev, S. (2007), Earthquake Resistant Confined Masonry

Construction. NICEE IIT-K.

6. Diana, M. S, (2012), Analytical Modelling of Masonry Infills. Acta

Technica Napocensis: Civil Engineering & Architecture Vol. 55 No. 2

(2012) 127-136.

7. European committee of standardization (CEN) (1996) Design of

Masonry Structure Part 1-1. General rules for Buildings Reinforcement

and unreinforced Masonry .ENN 1996 1-1 Euro Code 6, U. K.

8. FEMA 356 (1998). Evaluation of earthquake Damage Concrete and

Masonry wall Buildings Basic Procedure Manual ", Federal

Emergency Management Agency Washington D.C

9. Hirde, S., Bhoite, D. (2013). Effect of Modelling of Infill Walls onPerformance of Multistory RC Building. IJCIET, Volume 4, Issue 4,

July-August (2013). pp. 243-250.

10. IS 875:1960, Code of Practice for Structural Safety of Building:

Loading Standards. Bureau of Indian Standards, New Delhi.

11. IS 1893(Part 1): 2002, Criteria of Earthquake Resistant Design of

Structures. Bureau of Indian Standards, New Delhi.

12. Liauw and Kwan (1984). Plastic Design of Infilled Frames. Proc.,

Insti. Of Civil Engg., Part-II, Sept., pp. 367-377


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13. Mahmud, K., Islam, R., Al-Amin (2012). Study the Reinforced

Concrete Frame with Brick masonry Infill due to Lateral Loads.

IJCEE-IJENS Vol: 10 No: 04, pp.35-40.

14. Patel, S. (2012), Earthquake Resistant Design of Low-rise Open

Ground Storey Framed Building. M.Tech thesis (Major report), NIT

Rourkela.

15. Rivero, C. E., Walker, W. H., An Analytical Study of the Interaction of

Frames and Infill masonry Walls. Civil Engineering Studies, Structural

Research Series, no. 502, Urbana, Illinois, Sept. 1982.

16. Singh, S. K. (2000), Effect Of brick Masonry Infill on Seismic

behaviour Of R.C. frames. M.E. (Major Report), D.C.E. Delhi

17.Smith, B. Stafford (1966). Behaviour of Square Infilled Frames. J. Of

Struct. Div. ASCE, 92(1), Feb, pp. 381-403

18. Cuiqiang, Z., Ying, Z., Deyuan, Z. and Xilin, L.(2011). Study on the

Effect of Infill walls on the Seismic Performance of a Reinforced

Concrete Frame. Earthq Eng & Eng Vib (2011) 10: 507-517.

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