design of shear walls in response spectrum method and to ... · design of shear walls in response...

ISSN: 2455-2631 © March 2018 IJSDR | Volume 3, Issue 3

IJSDR1803015 International Journal of Scientific Development and Research (IJSDR) www.ijsdr.org 65

Design of shear walls in response spectrum method

and to study the effect of stiffness in high rise

buildings by using Etabs

1Channamallu Komali,

2Venkata Krishna Amaraneni

1M-Tech Student,

2Assistant Professor,

1Civil Engineering Department,

1Chalapathi Institute of Technology, Mothdaka, Guntur,

Abstract— Besides, food and clothing, shelter is a basic human need. India has been successful in meeting the food and

clothing requirements of its vast population; however the problem of providing shelter of all is defying solutions. Hence in

order to overcome this problem construction process should be quick, tall and effective to accommodate huge population

in a given area. So we have chosen this topic of “DESIGN OF SHEAR WALLS IN RESPONSE SPECTRUM METHOD

BY USING ETABS-2013”. “Design of shear walls” is the challenging task. Shear walls have a peculiar behavior towards

various types of loads. Calculation of lateral loads, shear force, storey shear, bending moment and displacements is a topic

of interest. We are going to check the building behaviour. We are verifying and designing this structure using extended

three dimensional analysis of buildings by (ETABS) software.

Index Terms— Shear walls, High rise buildings, Stiffness, Response Spectrum Method (key words)

________________________________________________________________________________________________________

I. INTRODUCTION

Shear walls are vertical elements of the horizontal force resisting system. Shear walls are constructed to counter the effects of

lateral load acting on a structure. In residential construction, shear walls are straight external walls that typically form a box

which provides all of the lateral support for the building. When shear walls are designed and constructed properly, and they will

have the strength and stiffness to resist the horizontal forces.

In building construction, a rigid vertical diaphragm capable of transferring lateral forces from exterior walls, floors, and roofs to

the ground foundation in a direction parallel to their planes. Examples are the reinforced-concrete wall or vertical truss. Lateral

forces caused by wind, earthquake, and uneven settlement loads, in addition to the weight of structure and occupants; create

powerful twisting (torsion) forces. These forces can literally tear (shear) a building apart. Reinforcing a frame by attaching or

placing a rigid wall inside it maintains the shape of the frame and prevents rotation at the joints. Shear walls are especially

important in high-rise buildings subjected to lateral wind and seismic forces.

In the last two decades, shear walls became an important part of mid and high-rise residential buildings. As part of an earthquake

resistant building design, these walls are placed in building plans reducing lateral displacements under earthquake loads. So

shear-wall frame structures are obtained.

Shear wall buildings are usually regular in plan and in elevation. However, in some buildings, lower floors are used for

commercial purposes and the buildings are characterized with larger plan dimensions at those floors. In other cases, there are

setbacks at higher floor levels. Shear wall buildings are commonly used for residential purposes and can house from 100 to 500

inhabitants per building.

II. SCOPE OF THE WORK

The aim of the shear wall is to investigate the different ways in which the tall structures can be stabilized against the effects of

strong horizontal wind loading and seismic loading. Some other reasons why we use shear walls are tall structures can be

constructed which reduces the area used and we can accommodate a large population in that particular area. Other objective is to

construct a cost effective structure in less period of time. This study helps in the investigation of strength and ductility of walls.

The scope is to analyze the constructed shear wall that is to be constructed. Firstly the model is implemented into known

computer software and then it is analyzed based on the investigation of strength and ductility. The strength of shear walls tested

are compared with the calculated strengths based on design codes



III. LITERATURE REVIEW

Development of shear wall system for construction has advanced dramatically over the past few years. Shear wall systems were

initially developed to reduce damage due to earth quakes labour requirements, increase strength of the building, shorten

construction time reduce cost increase quality of life.

U.H. Varyani described about shear walled buildings under horizontal loads. Considering in his design “Reinforced concrete

framed buildings are adequate for resisting both the vertical and the horizontal loads acting on shear walls of a building”. In this

2nd edition 2002 of “Design of structures”. He gave rigidity of shear wall, torsional rigidity and shear center of a building in a

detailed description.

S.K. Duggal on his profound interest on structures gave a detailed description about reinforced concrete buildings in his book

“ Earth quake resistant design of structures “describing a wall in a building which resist lateral loads originating from wind or

earthquakes are known as shear walls”. He considered flexural strength in the wall to be dominant force based on which design

of structure to be carried out in tall shear walls. He described in detail about various types of shear walls with their load bearing

capacities as per code requirements.

Mr A.P. Jadhav Associate Professor Rajarambapu Institute of technology rajaramnagar, Islampur has given a detailed report on

the form work used for the construction of shear walls. Mr.A.P.Jadhav highlighted the importance of quickness in construction

and the need for earthquake resistant building for better sustainability of life.

A report on effects of openings in shear walls on seismic response of structure by sharminriza chowdhary, department of civil

engineering dhake-1208, Bangladesh mostly focused on the design of shear walls with openings on seismic response using E-

Tabs, i.e extended three dimensional analysis of buildings. This report gives a detailed explanation of how ETABS can be

effectively used to design shear walls.

IV. DESIGN OF SHEAR WALLS

Shear walls construction is an economical method of bracing buildings to limit damage. For good performance of well-designed

shear walls, the shear wall structures should be designed for greater strength against lateral loads than ductile reinforced concrete

frames with similar characteristics; shear walls are inherently less ductile and perhaps the dominant mode of failure is shear. With

low design stress limits in shear walls, deflection due to shear walls is small. However, exceptions to the excellent performances of

shear walls occur when the height-to-length ratio becomes great enough to make overturning a problem and when there are

excessive openings in shear walls. Also, if the soil beneath its footing is relatively soft, the entire shear wall may rotate, causing

localized damage around the wall. Following are the design steps of cantilever shear walls.

General Requirements

(a) The thickness of the shear wall should not be less than 150mm to avoid unusually thin sections. Very thin sections are

susceptible to lateral instability in zones where inelastic cyclic loading may have to be sustained.

(b) The effective flange width for the flanged wall section from the face of web should be taken as least of

* Half the distance to an adjacent shear wall web, and

* One-tenth of total wall height.

(c) The minimum reinforcement in the longitudinal and transverse directions in the plan of the wall should be taken as 0.0025

times the gross area in each direction and distributed uniformly across the cross-section of wall. This helps in controlling

the width of inclined cracks that are caused due to shear.

(d) If the factored shear stress in the wall exceeds 0.25√fck or if the wall thickness exceeds 200mm, the reinforcement

should be provide in two curtains, each having bars running in both the longitudinal and transverse directions in the plane

of the wall. The use of reinforcement in two curtains reduces fragmentation and premature deterioration of the concrete

under cyclic loading.

Materials and Properties:

Type of frame: Special RC moment resisting frame fixed at the base

Seismic zone: II

Number of storey: Thirteen

Floor height: 3.0 m

Depth of Slab: 150 mm

Size of beam: (200 × 600) mm

Size of column: (450 × 450) mm

Spacing between frames: 5 m along x and 5m along y- directions

Live load on floor: 2 KN/m2

Floor finish: 1.5 KN/m2

Wall load: 10 KN/m



Materials: M 30 concrete, Fe 500 steel Material

Thickness of wall: 200 mm

Thickness of shear wall: 200mm

Density of concrete: 25 KN/m3

Density of infill: 20 KN/m3

Type of soil: Hard

Response spectra: As per IS 1893(Part-1):2002

Damping of structure: 3 percent.

Design Load Combinations

The design loading combinations are the various combinations of the pre- scribed response cases for which the structure is

to be checked/designed. The program creates a number of default design load combinations for a concrete frame design. Users

can add their own design load combinations as well as modify or delete the program default design load combinations. An

unlimited number of design load combinations can be specified.

To define a design load combination, simply specify one or more response cases, each with its own scale factor. The scale

factors are applied to the forces and moments from the analysis cases to form the factored design forces and moments for each

design load combination. There is one exception to the preceding for spectral analysis model combinations, any correspondence

between the signs of the moments and axial loads is lost. The program uses eight design load combinations for each such

loading combination specified, reversing the sign of axial loads and moments in major and minor directions.

Design Strength

The design strengths for concrete and steel are obtained by dividing the characteristic strength of the material by a partial

factor of safety, γ. The values of γ used in the program are as follows:

Partial safety factor for steel, γ = 1.15, and (IS456 36.4.2.1)s

Partial safety factor for concrete, γ= 1.5. (IS456 36.4.2.1)c

These factors are already incorporated in the design equations and tables in the code. Although not recommended, the program

allows the defaults to be overwritten. If the defaults are overwritten, the program uses the revised values consistently by

modifying the code mandated equations in every relevant place.

Boundary Conditions

There are the portions along the wall edges and may have the same or greater thickness than the wall web. These are

provided throughout the height with special confining reinforcement. Wall sections having stiff and well confined boundary

elements develop substantial flexural strength, are less susceptible to lateral buckling and have better shear strength and

ductility in comparison to plane rectangular walls not having stiff and well-confined boundary elements.

(a) During a severe earthquake, the ends of a wall are subjected to high compressive and tensile stresses. Hence, the

concrete needs to be well confined so as to sustain the load reversals without a large deterioration in strength.

Thus, the boundary elements are provided along the vertical boundaries of walls, when the extreme fibre

compressive stress in the wall due to factored gravity load plus factor earthquake force exceeds 0.2fck. The

boundary element may be discontinued where the calculated compressive stress becomes less than 0.15fck.

(b) The boundary element is assumed to be effective in resisting the design moment due to earthquake induced

forces, along with the web of the wall. The boundary element should have an adequate axial load carrying

capacity so as to carry an axial compression equal to the sum of the factored gravity load plus compressive load

due to seismic load.

(c) Moderate axial compression results in higher moment capacity of the wall. Hence, the beneficial effect of axial

compression by gravity loads should not be fully relied upon in a design, due to the possible reduction in its

magnitude by vertical acceleration. When gravity loads add to the strength of the wall, a load factor of 0.8 may

be taken

(d) The percentage of vertical reinforcement in boundary elements should range between 0.8 and 6 percent.

(e) During a severe earthquake, boundary elements may be subjected to stress reversals. Hence, they have to be

confined adequately to sustain the cyclic loading without a large degradation in strength. Therefore, these should

be provided throughout their height.

(f) Boundary elements need not be provided if the entire wall section is provided with special confining

reinforcement.

V. DESIGN OF G+13 SHEAR WALL BUILDING USING E-TABS

ETABS is sophisticated software for analysis and design program developed specifically for buildings systems. ETABS

version-2013.1.5 features an in intuitive and powerful graphical interface coupled with unmatched modelling, analytical, and



design procedures, all integrated using 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 nonlinear behaviors, making it the tool of

choice for structural engineers in the building industry.

Modelling

Firstly click on the ETABS icon .A window appears which shows a different tip every time you open the software. Change

the units at the right bottom to KN-m or any other as per your convenience. Click on file option to create a new file or to open

an already existing file. As we are creating a new file, we click on default.edb.

A new window appears which has Building plan grid system and Story data. In grid dimensions we can either use

uniform spacing or we can customize the grid spacing. We have to provide no of lines in x and y directions as per the

columns and beams used in the plan.

In the story dimensions, we have simple story data and custom story data. In simple story data, use the defaults or

specify values for the number of stories, typical story height, and bottom story height.

After providing the entire data click on grid only in structural objects and then click on ok.

Now the screen is divided into two equal halves in which one is plan view and the other is 3-D view of the provided data.

After the entire grid data and story data is provided, then we have to define the properties of the material that is used.

To define a material property, select define=>material properties. This makes us to either add new material, modify or

delete an existing material. Click on add new material to create a new material with required properties.

Firstly provide a name(say M20,M30 etc) and then provide the other properties of the material such as mass per unit

volume, weight per unit volume, elastic modulus, Poisson’s ratio. The other design properties that are to be provided are

characteristic compressive strength and yield strength values. You have other options such as change in display colour,

type of material which is always isotropic. After the entire data is provided click on ok.

The next step is to create beams and columns. To create a beam or column, first we click on define=>frame sections

command to create a beam or column. In this window we have import and add options further provided with modify or

delete options of already existing properties.

Provide the dimensions of the section as required and change the data according to the section provided. If a beam is to be

provided then select the design type to beam and provide the required dimensions to the cover and if a column is provided

select design type to column and then nominal cover is provided.

To create a column, the above process is repeated again and the only difference is the reinforcement data which is stated

earlier both for beams and columns.

To assign a beam, we can directly click on the icon create lines or region at click. The other way to do it is to click on

Draw menu=>Draw line objects=>Create lines or regions at click command. A window appears which provides properties

of the object in which the property is changed to the beam that we defined earlier. We can click on each grid point or

directly select all at once and the beams are assigned to the grid.

To assign a column, we can click on create columns in region or at clicks or click on Draw menu=>Draw line

objects=>Create columns in region or at clicks. In this the property is changed to the defined column and columns can be

assigned to offsets in x and y directions. Columns are also assigned in the similar way as beams are assigned.

Further we have to provide slabs for which we have to select define menu=>wall sections after which a window appears

with options add new, modify/show section and delete section. Click on add new slab and click on ok. A new window

appears where provide the section name as slab and the material is changed to the already defined one. The other data is

kept as it is. We can change the display colour to our convenience and then click ok.

To assign a slab, directly click on the draw rectangular areas and the other is to click on Draw menu=>Draw area

objects=>draw rectangular areas. The properties of the object are changed to the defined slab and then assigned to the end

points of the grid. The slab can be made visible by a click on Set Building view options on the top and the option object

fill is marked in special effects options.

After the slab is assigned to the structure the next step is to provide the wall for the structure which is the major portion of

the construction as we are providing shear walls. Shear walls are directly provided as that of slab with the help of a special

type of formwork using concrete. There is no role of bricks in this kind of wall. There are some requirements for shear

wall design i.e., the minimum thickness of the shear wall should be 150 millimeter or more.

Now for construction of a wall, firstly click define=>wall/slab/deck sections=>click to add new wall=>name the wall and

the material is selected as M30 and no more brick is used and then click ok without changing any other information.

To assign the wall, click directly on draw walls or create walls at click at the left side of screen or select draw=>draw area

objects=>draw walls or create walls at click and assign the walls at the required places. To make the wall visible, click on

SetBuilding options and the object fill is marked.

Assigning of loads:

After the columns, beams, walls and slabs are assigned now the loads are to be applied to the structure. There are

different load combinations used in this software. For shear walls, lateral loads and seismic loads play a vital role.

To assign any particular load, click Define=>Static load cases. In this window dead load and live load are already

assigned. To assign any other loads change the name of the load in load option, select the load type in type option,

add the self weight multiplier as required. The auto lateral load options provide different code books that are used

across the world. We use IS 1893-2002 code.



After we have defined the loads that are required to be provided for the structure, now the loads are need to be

assigned. For the loads that are acting on beams, select all the beams and then click assign=>frame/line loads

=>distributed=>select the load that is to be to assigned and then click ok.

For slabs and walls, select all the walls and slabs and then click on assign=>shell/area loads=>uniform. Select the

load that is to be assigned and then click ok.

To check whether the loads are assigned or not, click display=>show loads=>select joint/point or frame/line or

shell/area=>select the load that you need to check in load case and then click ok. The load is displayed in the plan

view at the center.

There are several load combinations that can also be designed depending on the requirements by selecting

define=>load combinations and then we can add numerous combinations as per the given code.

The additional loads that are to be defined are seismic and lateral loads for shear wall design. Hence quake and wind

loads are defined in both x and y directions and then they are assigned to the structure.

Analysis:

After all the loads are assigned, now click analyze=>run analysis. After the complete structure is analyzed, the

deformed shape of the structure is shown in 3D view. This is due to the loads that are acting on all the sections i.e.,

beams, columns, walls and slabs.

Fig 1- after analysis deflection diagram Fig 2- after analysis moment 3-3 diagram for dead load.

Fig.3 after analysis Shear force 2-2 diagram for dead load. Fig.4 after analysis storey lateral loads



Fig.5 after analysis Storey displacement

Fig.6 after analysis storey Shear

Fig.7 after analysis storey Stiffness



Fig.8 after analysis storey Shear

Design:

Fig.9 designing. Fig.10 after designing.



Fig.11 after designing reinforcement area.

VI. CONCLUSION

Thus shear walls are one of the most effective building elements in resisting lateral forces during earthquake. By constructing

shear walls damages due to effect of lateral forces due to earthquake and high winds can be minimized. Shear walls construction

will provide larger stiffness to the buildings there by reducing the damage to structure.

Not only has its strength, in order to accommodate huge number of population in a small area tall structures with shear walls

are considered to be most useful.

Hence for a developing nation like India shear wall construction is considered to be a back bone for construction industry.

REFERENCES

[1] U.H. Varnayi in his second edition of “Design of structures”

[2] S.K. Duggal in his “ Earth quake resistant design of structures” Page no:301 ,8.12 about Shear walls.

[3] S.K. Duggal in his “ Earth quake resistant design of structures “ pg.no:305 on flexural strength 8.14.1 case:1, case:2.

[4] S.K. Duggal in his “ Earth quake resistant design of structures” 8.16 Design of Shear walls which is also given in Is

code 13920:1993

[5] Mr A.P. Jadhav Associate Professor Rajarambapu Institute of technology rajaramnagar, Islampur has given a detailed

report on the form work used for the construction of shear walls.

[6] A report on effects of openings in shear walls on seismic response of structure by sharminriza chowdhary, department

of civil engineering dhake-1208, Bangladesh mostly focused on the design of shear walls with openings on seismic

response using E- Tabs

[7] I.S 456:2000

[8] As per clause 32, design for wall describes, design of horizontal shear in clause 32.4 given details of how shear wall

have to be constructed.

[9] I.S:1893 Criteria of Earth Quake resistant Buildings Part (3) page 23, clause 4.2 gives the estimation of earth quake

loads.

[10] In IS: 13920:1993 it gives the ductile detailing of shear wall as per clause 9.

[11] Ductile detailing, as per the code IS: 13920:1993 is considered very important as the ductile detailing gives the amount

of reinforcement required and the alignment of bars

design of shear walls in response spectrum method and to ... · design of shear walls in response...

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