In the present study main focus was the location of shear wall and so in this project we did analysis of a multi-storey building.In the seismic design of buildings, shear wall act as major earthquake resisting members. Structural walls provide an efficient bracing system and offer great lateral load resistance. The properties of these shear walls dominate the response of the buildings, and therefore, it is important to evaluate the seismic response of the walls appropriately. The analysis was carried out in ETABS 2015 software. We did the comparative analysis of the building with and without shear wall. Parameters like lateral displacement, storey drift were calculated in both the cases.
List of Figures
Figure No. Figure Description Page No.
Fig. 1.1 Destructions due to Earthquake 1
Fig. 1.2 Classification of shear Wall based on Height to Depth Ratio 3
Fig. 3.1 Lateral Load Resisting System 15
Fig. 5.1 Software Input 26
Fig. 5.2 Display of model of building without shear wall 27
Fig. 5.3 Load Combinations 28
Fig. 5.4 Analysis in ETABS software showing displacement pattern 29
Fig. 5.5 Maximum Storey Displacement Result display 30
Fig. 5.6 Graph showing Displacement at each storey 30
Fig. 5.7 Storey Drift Result Display 31
Fig. 5.8 Graph showing Storey Drift 31
Fig. 5.9 Building with Shear Walls 32
Fig. 5.10 Input of dimensions of Shear Wall 33
Fig. 5.11 Deformed Shape of Building with shear wall 34
Fig. 5.12 Bending Moment Diagram 34
Fig. 5.13 Maximum Storey Displacement Results Display 35
Fig. 5.14 Graph Showing Maximum Storey Displacement 35
Fig. 5.15 Display of Storey Drift 36
List of Tables
Table No. Table Description Page No.
Table I Preliminary Data 24
Table II Result Comparison 38
Table of Contents
List of Figures iii
List of Tables iv
Chapter - 1 Introduction 1
1.1 Introduction 1
1.2 What is shear wall 2
1.3 Types of shear wall 3
1.4 Advantages of shear wall 3
Chapter - 2 Literature Review 4
2.1 Articles/ Paper Found 1 4
2.2 Articles/ Paper Found 2 10
Chapter - 3 Lateral Load Resisting Systems 14
3.1 Structural Systems 14
3.2 Seismic Methods of Analysis 16
3.3 Seismic Coefficient Method 18
Chapter - 4 Basics of Earthquake Engineering 20
4.1 Terminologies Related to Earthquake Engineering 20
4.2 Requirements of shear wall as per IS:13920 - 1993 22
Chapter - 5 Modelling and Simulation 23
5.1 Introduction to ETABS 23
5.2 Design Problem 24
5.3 Parameters to be considered 25
5.4 Model-1 - Building without Shear wall 26
5.5 Load cases taken into consideration 28
5.6 Model-2 - Building with Shear wall 32
Chapter - 6 Results and Conclusion 38
Chapter - 7 Future Scope 39
Chapter - 8 PMMS Activity 40
Chapter-9 Canvas Making 41
9.1 Product development canvas 41
9.2 AEIOU summary sheet 41
9.3 Empathy mapping canvas 42
9.4 Ideation Canvas 42
Chapter-10 Bibliography 43
Chapter 1 : Introduction
Earthquake is a natural phenomenon which occurs without any prior notice i.e. it is uncertain. The aim of engineering design is to link economics, cultural, social, and environmental and safety factor to produce the best solution. India is a large country with large part of its area earthquake prone. Most part of rural and urban buildings are low-rise buildings not of more than three stories. Many of them are not accurately designed by engineers trained in earthquake engineering. Major loss of life and property due to earthquakes is caused due to collapse of buildings. The number of residential units and other small-scale constructions might increase a lot in the coming two decades in India and other developing countries of the world because of the need for a simple engineering approaches to make such buildings earthquake resistant and economical.
The behaviour of a building during earthquakes depends critically on its design, but also on how the earthquake forces are carried to the ground. The main objective of seismic resistant construction is that the structure does not collapse during less magnitude earthquakes. This also helps in preventing failure of the structure giving sufficient warning during severe earthquakes thereby saving precious lives and property.
Fig. 1.1 Destructions due to earthquake
1.2 What Is a Shear Wall?
Shear Wall is a rigid structural component of a Building to resist the effects of the lateral loads acting on the structure. Shear Wall is a wall that is designed to resist shear, the lateral force that causes damage in earthquakes. Reinforcing a frame by attaching or placing a rigid wall inside it maintains the shape of the frame and resists the rotation of members at the joints. Shear walls are especially important in high-rise buildings subject to lateral wind and seismic forces. An effective wall should be both stiff and strong. Stiffness alone will not be enough, as the member becomes stiffer, the more brittle it becomes. Strength alone is not sufficient.
Factors Governing Performance of Shear Wall
Some of the Factors that affect the behavior of shear wall are as under:-
The term is loosely used in earthquake engineering is to indicate the amount to which an assembled structure that is damaged, can undergo large deformations without collapsing.
In brief it is the ratio of displacement at maximum load to that at yield.
It is the property of a element to resist displacement.
Soil Structure Interaction Effects :-
Structural damage is directly related to depth of soil lying over the rock and period of vibration of soil.
Understanding the relation between period of vibration of soil and structure is important.
Period of Structure :-
It is important index that identifies vulnerability to excessive drift.
1.3 Types of Shear Wall
Shear walls can be classified as load-bearing or non-load-bearing, depending on whether they carry gravity loads also along with the lateral load. They can be classified based on the type of masonry and construction used, for example, concrete or brick, reinforced and unreinforced, single story or multi-storey, solid or perforated, rectangular or flanged, cantilever or coupled, etc.
Shear walls (monolithic) can be classified as short, cantilever or squat according to their height to depth ratio.
Fig. 1.2. Classification of shear Wall based on Height to Depth Ratio
1.4 Advantages of Shear Wall
An accurately designed and detailed building with shear walls has shown very good performance in past earthquakes. The extraordinary Success of buildings with shear walls in resisting strong earthquakes is summarized in the quote:
“We cannot afford to build concrete buildings meant to resist severe earthquakes without shear walls”
- Mark Fintel, a noted consulting Engineer in USA
Shear Wall buildings are a popular choice in many countries like Chile, New Zealand and USA. Shear Walls are easy to construct, because reinforcement detailing of walls is relatively straight-forward and so it is easily implemented on site. Shear Walls are efficient, both in terms of construction cost and effectiveness in minimizing earthquake damage in structural and non-structural elements.
CHAPTER 2 : LITERATURE REVIEW
2.1 Articles / Papers Found
Seismic Analysis of RCC Building with and Without Shear Wall
-by P. P. Chandurkar, Dr. P. S. Pajgade
In the seismic design of buildings, reinforced concrete structural walls, or shear walls, act as major earthquake forces resisting members. Structural shear walls provide an efficient bracing system and offer great lateral load resistance. The properties of these shear walls dominate the response of the buildings, and therefore, it is important to calculate the seismic response of the walls appropriately. In this present study, main focus is to determine the solution for location of shear wall in multi-storey building. Effectiveness of shear wall has been studied with the help of four models. Model one is bare frame structural system and other three models are dual type structural system. An earthquake load is applied to a building of G+9 stories located in zone 2, zone 3, zone 4 and zone 5. Parameters like Maximum Lateral displacement, story drift and total cost required for ground floor are calculated in both the cases replacing column with shear wall. In the present paper one model for bare frame type residential building and three models for dual type structural system are generated with the help of ETABS software and effectiveness of it has been checked.
Results / conclusions :-
For model 1
For model 2
For model 3
For model 4
For model 1
For model 2
For model 3
For model 4
2.2 Articles / Papers found
Seismic Analysis of Building with Shear Wall
-by Prasad Ramesh Vaidya
This study is about the seismic performance of shear wall building on a sloping ground. The main objective of this is to understand the behaviour of the building on sloping ground for various locations of shear walls and to study the effectiveness of shear wall in a building on a sloping ground. The behaviour of the building has been studied with the help of four models. Model one is of frame type structural system and other three models are of dual type (shear wall- frame interaction) structural system with three different positions of shear walls. Response spectrum analysis is carried out by using SAP 2000 which is finite element software. The performance of building with respect to displacement, story drift has been presented in this paper.
Results / conclusions:
Results of response spectrum analysis as per IS 1893:2002 (Part I) on the above four models with respect to displacement, storey drift, are shown below. Percentage reduction in bending moment, shear force and torsional forces as compared with frame type structural system is also represented in the following paper.
Displacement profile for the above models along both the principle directions is shown in figures. In the direction of ground slope displacement is found to be minimum in model 3 (Shear wall provided towards long column side). The roof displacement for model 3 is reduced up to 43.62% as compared with model 1 and about 43.38% as compared with model 2. In other direction where ground profile is flat Model 4 gives minimum displacement.
Comparison of storey drift for above four models is as shown in figure. Storey drift for model 3 (shear wall towards long column side) is minimum along sloping side, where as on other side model 1 give minimum drift. Storey drift for shear wall frame interaction system is more than frame type structural system along other side of building this may be because of irregular stiffness. On sloping side top storey drift for model 2 is reduced up to 94.6% as compared with model 1
Chapter 3 : Lateral Load Resisting Systems
3.1 Structural systems
Earthquake causes shaking of ground in all the planar directions along the two horizontal directions (X and Y) and the vertical direction (Z). All Structures are primarily designed to carry vertical forces. However, horizontal shaking along X and Y directions remains a matter of concern.
There are main four structural systems to resist lateral loads.
(a) Load Bearing wall System
(b) Moment Resisting Frame System
(c) Dual Systems (Frame + Shear Wall/Bracing)
(d) Tube Systems
The load bearing wall system is suitable for low-rise buildings. However, this system is very weak in resisting lateral loads and is seldom recommended for multi-storey building.
The framework of multi-storey building consists of no. of beams and columns built monolithically, forming a framework. The system comprising of RC columns and connecting beams is called RC frame. The ability to resist lateral forces depends on rigidity of joints between beams and columns. When these are fully rigid, the structure as a whole is capable of resisting the lateral loads. Such type of frame is called Moment Resisting Frame.
However, if the strength and stiffness of a moment resisting frame are not adequate, the frame may be strengthened by incorporating structural components such as load bearing shear walls, Shear Wall with columns, Infilled shear walls, Bracings, Diaphragms.
Shear walls and bracings are also useful in preventing failure of non-structural components by reducing drift. These may be of RCC, steel, composite and masonry. Shear wall is a vertical plate like RC wall. These walls generally start from level of foundation and are continuous throughout the building height. Shear walls are like vertically oriented wide beams that carry earthquake loads from diaphragm and transmit them to the ground.
Braced Frames behaves similar to the shear walls, but they may offer lower resistance depending on their design and construction. Bracing generally takes form of steel rolled sections, circular bar sections or tubes. Vibration may cause the bracing to elongate or compress.
Diaphragms are horizontal resistance elements, generally floors and roofs that transfer the lateral forces between vertical resistance elements (shear wall or frames). Basically diaphragm acts as a horizontal I-beam i.e. diaphragm itself acts as the web of beam and its edges acts as flanges.
For the buildings taller than about 40 storeys, the effect of lateral forces becomes very intense. In such cases, Tube Systems are more economical than the moment resisting frames.
Fig.3.1. Lateral Load Resisting System
3.2 Seismic Methods of Analysis
Once the Structural Model has been selected, it is possible to perform analysis to different degree of accuracy. The analysis process can be classified based on three factors: the external action, the behaviour of structure and the type of structural model selected.
Based on the type of external action and behaviour of structure, the analysis can further classified as:-
Linear Static Analysis
Linear Dynamic Analysis
Non- Linear Static Analysis
Non- Linear Dynamic Analysis
Methods of Elastic Analysis covered under IS 1893 (Part- I ) - 2002 are,
1. Seismic Coefficient Method or Static Coefficient Method
2. Response Spectrum Method or Modal Method
3. Elastic Time History Method
1. Seismic Coefficient Method
Seismic Analysis of most of the structures is still carried out on the basis of lateral force assumed equivalent to the actual (dynamic) loading. Although earthquake force is dynamic, the routine analysis is done by assuming it to be static. The base shear which is the total horizontal force acting on the structure is calculated on the basis of structure mass, fundamental period of vibration and corresponding mode shape. Base shear is distributed along the height of the structure. This method is simplest and requires fewer calculations. This method is usually conservative for low and medium height buildings with regular configurations.
2. Response Spectrum Method
This method is applicable for those structures where modes other than fundamental one affect significantly the response of the structure. Generally, this method is applicable to analysis of dynamic response of structures, which are asymmetrical or have area of irregularity or discontinuity, in their linear range of behaviour. This method is based on the fact that, for certain damping, which are reasonable models for many buildings, the response in each natural mode of vibration can be computed independently of others, and modal responses can be combined to determine the total response.
3. Elastic Time History Method
A linear time history analysis overcomes all the disadvantages of a modal response spectrum analysis, provided non-linear behaviour is not involved. This method requires greater computational efforts for calculating the response at discrete times. Advantage of such a procedure is the relative signs of response qualities are preserved in the response histories. This is important when interaction effects are considered among stress resultants.
3.3 Seismic Coefficient Method
In this method, firstly the design base shear is calculated for the whole building, and it is then distributed along the height of the building.
(1) Determination of Base Shear:
The total design lateral force or design seismic base shear (VB) along any principal direction shall be determined by following expression:
IS: 1893(1) - 2002 ; Cl. 7.5.3
VB = Total Design lateral force at the base of a structure.
Ah = Design horizontal acceleration spectrum value
W = Seismic Weight of the Building
IS: 1893(1) - 2002; Cl. 6.4.2
Z = Zone Factor
I = Importance Factor
R = Response Reduction Factor
Sa/g = Avg. response acceleration coefficient
(2) Distribution of Base Shear
The base shear calculated above is to be distributed along height of building. The shear force at any level depends on mass at that level and deformed shape of structure. Earthquake studies indicate top portions suffer more damage than lower one.
The design base shear (VB) shall be distributed along the height of the building as per the following expression
Qi = Design Lateral Force at floor i,
Wi = Seismic Weight of floor i,
hi = Height of floor i measured from base,
n = Number of Storeys
Chapter 4 : Basics of Earthquake Engineering
4.1 Terminologies Related to Earthquake Engineering
The effect of internal friction, imperfect elasticity of material, sliding, slipping, etc in reducing the amplitude of vibration and is expressed as a percentage of critical damping.
(2) Design Horizontal Acceleration Coefficient (Ah)
It is a horizontal acceleration coefficient that shall be used for design of structures.
(3) Design Lateral Force
It is the horizontal seismic force prescribed by this standard that shall be used to design a structure.
(4) Importance Factor (I)
It is a factor used to obtain the design seismic force depending on the use of the facility of the structure, characterised by hazardous consequences of its failure, its post-earthquake functional need, historic value, or economic importance.
(5) Modal Mass ( Mk)
Modal mass of a structure subjected to horizontal or vertical, as the case maybe, ground motion is a part of the total seismic mass of the structure that is effective in mode k of vibration. The modal mass for a given mode has a unique value irrespective of scaling of
the mode shape.
(6) Fundamental Natural Period
It is the first (longest ) modal time period of vibration.
(7) Modal Natural Period
The modal natural period of mode k is the time period of vibration in mode k.
(8) Response Reduction Factor (R)
It is the factor by which the actual base shear force, 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.
(9) Seismic Mass
It is the seismic weight divided by acceleration due to gravity.
(10) Seismic Weight (W)
It is the total dead load plus appropriate amounts of specified imposed load.
(11) Structural Response Factors ( Sa/g )
It is a factor denoting the acceleration response spectrum of the structure subjected to earthquake ground vibrations, and depends on natural period of vibration and damping of the structure.
(12) Zone Factor (Z)
It is a factor to obtain the design spectrum depending on the perceived maximum seismic risk characterized by Maximum Considered Earthquake ( MCE ) in the zone in which the structure is located. The basic zone factors included in this standard are reasonable estimate
of effective peak ground acceleration.
(13) Shear Wall
It is a wall designed to resist lateral forces acting in its own plane.
(14) Soft Storey
It is one in which the lateral stiffness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stiffness of the three storeys above.
(15) Storey Drift
It is the displacement of one level relative to the other level above or below.
4.2 Requirements of shear wall as per IS : 13920 - 1993
(i) The thickness of wall shall not be less than 150 mm .
(ii) Shear walls shall be provided with reinforcement in the longitudinal and transverse direction in the plane of the wall, not less than 0.25 % of gross area in each direction.
(iii) If the factored shear stress in the wall exceeds 0.25 √(f_ck ) , or the wall thickness exceeds 200 mm, reinforcement shall be provided in two curtains, each having bars running in the longitudinal and transverse direction in the plane of the wall.
(iv) The diameter of the bar used in any part of the wall shall not exceed 1/10 th of the thickness of that part.
(v) The maximum spacing shall not exceed the smaller of the followings:
(a) lw where,
(b) 3 * tw lw = horizontal length of wall
(c) 450 mm tw = thickness of wall web
Chapter 5 : Modelling and Simulation
5.1 Introduction to Software
ETABS is software which is easy to use, special purpose analysis and design program developed specially for building systems. ETABS features a powerful graphical interface coupled with best modeling, analysis, and design procedures, all combined using a common database. Although quick and easy for simple structures, ETABS can also handle the largest and most complex building models, including a wide range of geometrical nonlinear behaviours, making it the tool of choice for structural engineers in designing.
The accuracy of analytical modelling of complex Wall Systems has always been of concern to the Structural Engineer. The computer models of these systems are usually idealized as line elements instead of continuum elements. Single walls are modelled as cantilevers and walls with openings are modelled as pier and spandrel systems. For simple systems, where lines of stiffness can be defined, these models can give a reasonable result. However, it has always been recognized that a continuum model based upon the finite element method is more appropriate and desirable. Nevertheless this option has been impractical for the Structural Engineer to use in practice primarily because such models have traditionally been costly to create, but more importantly, they do not produce information that is directly useable by the Structural Engineer. However, new developments in ETABS using object based modelling of simple and complex wall systems, in an integrated single interface environment, has made it very practical for Structural Engineers to use finite element models routinely in their practice.
5.2 Design Problem
The Codes followed for the Study were:-
IS 456 : 2000
IS 875-Part I to Part V : 1987
IS 13920 : 1993
IS 1893 : 2002
For our study, a 10 storey building with a 3m height for each storey, regular in plan is modeled. Building is assumed to be fixed at base and floors acts as rigid diaphragms. The Sections of the structural elements are square and rectangular. Storey heights are assumed to be constant including the ground storey. Building is assumed to be located in Vadodara, Gujarat having design wind speed 44kmph (as per IS: 875-part3). The buildings are modeled using software ETABS 2015. Models are studied and results of Maximum Storey Displacement and Story Drift is carried out.
For Ten Story
No. of Stories G + 9
Floor to Floor Height 3 m
Beam Size Longitudinal and Transverse Direction 250 x 450 mm
Column Size 600 x 600 mm
Thickness of Slab 125 mm
Grade of Concrete and steel M-20 and Fe-415
Earthquake Zone III
Table I- Preliminary Data
5.3 Parameters to be compared
(1) Storey Drift
When a building is subjected to earthquake forces, the floors are deflected laterally. The drift in a storey is computed as a difference of deflections of the floors at the top and bottom of the storey under consideration. The total drift in any storey is the sum of the shear deformations of that storey, axial deformation of floor systems, overall flexure of the building (axial deformation of columns). Due to minimum specified design lateral force, the storey drift in any storey with partial load factor of 1.0 should not exceed .004 times the storey height.
Storey Drift is limited during earthquake for the following reasons:
Limitations on the use of building,
Adverse effects on the behaviour of non-load bearing elements,
Degradation in the appearance of the building,
Discomfort for the occupants.
To limit damage to non-structural members
Preserve Vertical stability of a structural system.
To limit the effects of eccentric gravity loads.
(2) Maximum Storey Displacement
The lateral displacement of any particular storey in any direction is called maximum storey displacement.
Maximum Storey displacement should be limited from H/300 to H/500.
5.4 MODEL 1:- Building Without Shear Wall
For the Comparative analysis we first modeled a structure without shear wall.
Design Steps Followed:
(1) Data Input:
The data mentioned above were entered in the starting screen of ETABS 2015.
Fig. 5.1. Software Input
The first model was designed with a building without shear wall. The Screenshot below shows the 3D model of the same.
Fig. 5.2 Display of model of building without shear wall
5.5 Load Cases taken into considerations for analysis
(1) Dead Load (DL)
(2) Live Load (LL)
(3) Wind Load (WL)
(4) 1.5 (DL + LL)
(5) 1.2 (DL + LL + EQX)
(6) 1.2 (DL + LL + EQY)
(7) 1.5 (DL + EQX)
(8) 1.5 (DL + EQY)
Fig.5.3 Load Combinations
The displacement pattern of the structure can be seen by running the analysis of the model.
Displacements at different points can be known after running this analysis.
Fig.5.4 Analysis in ETABS software showing displacement pattern
Results can be evaluated after performing the analysis of model.
Various aspects such as maximum storey displacement, storey drift, reactions at base can be obtained.
The screenshot below shows the maximum story displacement for the most critical load combination.
Fig.5.5 Maximum Storey Displacement Result display
Fig.5.6 Graph showing Displacement at each storey
Result about the maximum storey drift are obtained for the maximum magnitude of load among all the loads.
The graph of drift vs. storey can be obtained along with the values at each storey level.
Fig.5.7 Storey Drift Result Display
Fig.5.8 Graph showing Storey Drift
5.6 Model - 2 : Building With Shear Wall at it Corners
After performing the analysis of building without shear wall, we have created a model of the building having same specifications with shear wall.
Shear walls are selected to be located at all the four corners of the building starting from the foundation to the topmost storey.
The screenshot below shows the 3D model view of the building with shear wall at its corners.
Fig.5.9 Building with Shear Walls
After inputting the preliminary data, the specifications of the wall are to be added as under:
Specifications of Shear Wall
Shape of Wall - L shaped
Length of wall in both X and Y direction - 5 m
Thickness of wall - 300 mm
Screenshot below shows the window in which the data regarding the wall dimensions are entered.
Fig.5.10 Input of dimensions of Shear Wall
On performing the analysis of building with shear wall the deflection pattern is produced as below:
Fig.5.11 Deformed Shape of Building with shear wall
The bending pattern of the structure can be shown in the figure below.
Fig.5.12 Bending Moment Diagram
The graph of Maximum Storey Displacement vs. Storey, with values can be obtained as shown in screenshot as under:
It can be seen that the storey displacement in higher floors is higher in upper storeys.
Fig.5.13 Maximum Storey Displacement Results Display
Fig.5.14 Graph Showing Maximum Storey Displacement
The relation between Storey Drift vs. Storey is as shown below.
From the values it can be observed that the values for drift in building with shear wall the storey drift is reduced considerably.
Fig. 5.15 Display of Storey Drift
Chapter 6 : Result and Conclusion
STOREY DRIFT MAXIMUM
X DIR. (mm) Y DIR. (mm) X DIR. (mm) Y DIR. (mm)
Building Without Shear Wall 1.21 1.21 22.979 22.979
Building With Shear Wall 0.1 0.2 1.109 2.673
Table II - Result Comparison
From the above comparison it can be derived that in a building with shear wall the storey drift and maximum storey displacement is reduced by a considerable amount. The Storey Displacement in the building was more than the tolerable limit i.e. height of storey divided by 500. The Maximum Storey displacement of the building with shear walls at its corners is well under the allowable limit of displacement.
Thus it can be concluded that it is advisable to provide shear wall in a building so that damages due to earthquake can be minimized and most importantly, the valuable life can be saved.
Chapter 7 : Future Scope
Static analysis of the multi storey building with shear wall at various places.
Dynamic analysis and time history analysis
Cost analysis of the various building components and will compare the results with and without shear wall.
Chapter 8 : PMMS Activity
Chapter 9 : Canvas Making
9.1 Product development canvas
In this canvas we have to stick according to the headings which are fully related to the product of our domain (topic).
9.2 AEIOU Summary Sheet
A-Activity, E- Environment, I-Interaction, O-Objects, U- Users.
9.3 Empathy Mapping Canvas
In this canvas, we have to find out what is user to our problems? What is a stakeholder? What are activities? And what are broad stories of their activates those are 2 sad and 2 happy.
9.4 Ideation Canvas
From the user canvas, you have an idea what are the people? In ideation canvas, you have to carry out which type of activities is related to our project and people? What is situation and location regarding to activities? Then find the possible solutions.
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