Shear Wall Design of A G+2 Structure in STAAD Pro

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ISSN 2319-8885

Vol.06,Issue.21

June-2017,

Pages:4101-4108

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Shear Wall Design of A G+2 Structure in STAAD Pro P. LAKSHUMAIH CHOWDARY

1, SAMPANGI AMARTESH

2

1Associate Professor, Dept of Computer Aided Structural Engineering, BITS College, Adoni, Kurnool(Dt), AP, India.

2PG Scholar, Dept of Computer Aided Structural Engineering, BITS College, Adoni, Kurnool(Dt), AP, India.

Abstract: A shear wall is a structural system composed of braced panels (also known as shear panels). Reinforced concrete (RC)

buildings often have vertical plate-like RC walls called Shear Walls in addition to slabs, beams and columns. These walls used to

counter the effects of lateral load acting on a structure. Wind and seismic loads are the most common loads that shear walls are

designed to carry. Shear walls resist in-plane loads that are applied along its height. The applied load is generally transferred to

the wall by a diaphragm or collector or drag member to the foundation. Shear walls are easy to construct, because reinforcement

detailing of walls is relatively straight-forward and therefore easily implemented at site. Shear walls are efficient, both in terms

of construction cost and effectiveness in minimizing earthquake damage in structural and non-structural elements (like glass

windows and building contents.).

Keywords: Reinforced concrete (RC), Load Matrix, Stiffness Matrix, Displacement Matrix.

I. INTRODUCTION Construction is a complex process involving basically the

areas of Architectural planning, Engineering &

Construction. There is growing realization today that speed

of construction needs to be given greater importance

especially for large housing projects. The traditional mode

of construction for individual houses comprising load

bearing walls with an appropriate roof above or reinforced

concrete framed structure construction with infill masonry

walls would be totally inadequate for mass housing

construction industry in view of the rapid rate of

construction. Further, such constructions are prone to poor

quality control even in case of contractors with substantial

resources and experience. Structural design in an art of

science of designing, with economy and elegance, a safe

serviceable and durable structure. The process of designing

commences with the planning of the structure, primary to

meet the functional requirements of the user. The

requirements delivered by the client may not be well

defined and may be vague also but it is the work of the

designer to understand the needs and design the structure

accordingly.

The functional requirements and economy of the structure

for its intended use over the life span of the structure are

intended to by the structural designer. Shear walls in

buildings must be symmetrically located in plan to reduce

ill-effects of twist in buildings. They could be placed

symmetrically along one or both directions in plan.

Individual wall may be subjected to axial, translational, and

torsional displacements. The extent to which a wall will

contribute to the resistance of overturning moments, storey

forces, and storey torsion depends on its geometric

configuration, orientation and location within the plane of

the building. Under the large overturning effects caused by

horizontal earthquake forces, edges of shear walls

experience high compressive and tensile stresses. To ensure

that shear walls behave in a ductile way, concrete in the

wall end regions must be reinforced in a special manner to

sustain these load reversals without losing strength. End

regions of a wall with increased confinement are called

boundary elements. This special confining transverse

reinforcement in boundary elements is similar to that

provided in columns of RC frames.

Statement of project Salient features:

Utility of building: Residential complex

Number of stories: G+2

Ground floor: 3m

Floor to floor height: 3m

Total height of the structure: 39m

Total length of the building in X direction = 45m

Total length of the building in Y direction = 45m

Slab thickness: 150mm

Materials: Concrete grades: M20, M25

Steel grades: FE415, FE500

Material properties

The following materials are used in this project.

P. LAKSHUMAIH CHOWDARY, SAMPANGI AMARTESH

International Journal of Scientific Engineering and Technology Research

Volume.06, IssueNo.21, June-2017, Pages: 4101-4108

Table1. Concrete material

The M20 Concrete used for all slabs and beams.

The M25 concrete used for all columns

Table2. Steel properties

Fe 500 steel used for longitudinal reinforcement.

Fe 415 steel used for transverse reinforcement for analysis.

Software :This project is mostly based on software and it

is essential to know the details about these software’s. List

of software’s us

II. STATIC AND DYNAMIC LOADS

A. Typical Dynamic Loadings (Adapted from dynamics

of structures Ray W. Clough & Joseph Penzien, 2003)

Fig1.

Statics deals with the effect of forces on bodies at rest.

The term dynamic may be defined simply as time-varying;

thus a dynamic load is any load of which its magnitude,

direction, and/or position varies with time. Similarly, the

structural response to a dynamic load, i.e., the resulting

stresses and deflections, is also time-varying, or dynamic.

Two basically different approaches are available for

evaluating structural response to dynamic loads:

deterministic and nondeterministic. The choice of method to

be used in any given case depends upon how the loading is

defined. If the time variation of loading is fully known, even

though it may be highly oscillatory or irregular in character,

it will be referred to herein as a prescribed dynamic loading;

and the analysis of the response of any specified structural

system to a prescribed dynamic loading is defined as a

deterministic analysis. On the other hand, if the time

variation is not completely known but can be defined in a

statistical sense, the loading is termed a random dynamic

loading; and its corresponding analysis of response is

defined as a nondeterministic analysis. In general, structural

response to any dynamic loading is expressed basically in

terms of the displacements of the structure. Thus,

deterministic analysis leads directly to displacement time-

histories corresponding to the prescribed loading history;

other related response quantities, such as stresses, strains,

internal forces, etc., are usually obtained as a secondary

phase of the analysis. On the other hand, a nondeterministic

analysis provides only statistical information about the

displacements resulting from the statistically defined

loading; corresponding information on the related response

quantities are then generated using independent

nondeterministic analysis procedures.

B. Linear analysis

The linearity of a mechanical system depends upon the

linearity of its components which are mass, stiffness and

damping. Linearity implies that the response of each of these

components (i.e. acceleration, displacement, and velocity,

respectively) bears a straight line or linear relationship to an

applied force. Stress is proportional to strain. The straight

line relationship must extend over the whole range of

movement of the component, negative as well as positive.

All the principle of superposition are also valid. In linear

analysis we do not consider any cracking effects not do we

look for strength loss. In Linear analysis Structure returns to

original form No changes in loading direction or magnitude

Material properties do not change Small deformation and

strain In linear elastic analysis, all that happens(basically,

when you create a model) is [F] = [K][X] (Load matrix,

stiffness matrix and displacement matrix) equation is solved

and that's the end. One major assumption made here is that

axial force and bending moment are independent of one

another! In reality, they interact. This leads to geometrical

nonlinearity.

C. Non-linear analysis

Non-linear analysis always is a great challenge and it can

be frustration. In nonlinear analysis Stress is no longer

proportional to strain. If a member goes beyond its capacity

(elastic limit), it will experience some sort of strain

hardening or cracking and it will start losing its stiffness

which also means that the total stiffness of the structure or

Shear Wall Design of A G+2 Structure in STAAD Pro



building is also changing. When the materials move into the

zone beyond its yield strengths, it no longer behaves in a

linear fashion.

Fig2. Non-linear analysis.

There are many things that happen when material go into

this zone:

1. Permanent deformations: This means that when the

material is unloaded it will not go back to its original

shape or position. For example if you take a plastic bag

and stretch it, after a certain point even if you release the

bag you will see the permanent stretch marks. This is

called permanent deformation.

2. Cracking: Generally this occurs in linear design as

well, but we neglect the cracking of concrete, even

though we still consider the reduced stiffness of

members while doing seismic design, but still it is an

assumed value. While in nonlinear analysis we monitor

the cracking and so concrete will crack and member will

start losing its stiffness.

3. Beam rotations: When a beam is subjected to moments

greater than its capacity, it no longer resists the

moments, instead it rotates and forms a plastic hinge and

start dissipating energy. This is a part of material

nonlinearity but for beams it is called backbone curve

(aka FD relationship). In case of linear design we do not

case for anything greater than the capacity of the

member

4. Energy Dissipation: In linear analysis, energy

dissipation is in the form of strain energy, while in case

of nonlinear analysis it is in the form of inelastic energy

in addition to strain energy dissipation.

D. Types of Nonlinearity

1. Nonlinear Material

Materials that do not have a complete linear stress strain

curve as seen in plastic and rubber materials for

example .The material starts to yield, then the stress

strain curve changes.

2. Nonlinear Geometry

The changing shape of a model when large deformations

exists provide nonlinear changes in the components

stiffness.

Geometrical nonlinearity usually consists of two effects:

Effect of Axial strain on bending moment: P-Delta

effects.

Effect of bending strain on axial stiffness: presence of

axial force reduces bending stiffness, presence of

bending moment also reduces axial stiffness. And once

again, this interaction renders the analysis nonlinear and

there is no F=KX anymore.

The most famous geometric nonlinearity is P-Delta

analysis.

3. Nonlinear Boundary Condition

Boundary conditions that involve components in contact

with one another often produce disproportionate

changes in deformation.

4. Nonlinear Loading Condition

Loading changes over time.

If the loss in stiffness is significant and the results or the

energy balance do not converge, we iterate the same process

and do the analysis again. This cycle will go on till the

desired accuracy is achieved. Thus a nonlinear analysis takes

longer than a linear analysis because of such loses in

stiffness and its iterative nature.

III. SHEAR WALL ANALYSIS

A shear wall is a structural system composed of braced

panels (also known as shear panels).Reinforced concrete

(RC) buildings often have vertical plate-like RC walls

called Shear Walls in addition to slabs, beams and

columns. These walls used to counter the effects of lateral

load acting on a structure. Wind and seismic loads are the

most common loads that shear walls are designed to carry.

Shear walls resist in-plane loads that are applied along its

height. The applied load is generally transferred to the

wall by a diaphragm or collector or drag member to the

foundation. The shear walls requirements given in IS

13920: 1993 code book. These walls generally start at

foundation level and are continuous throughout the

building height. Their thickness can be as low as 150mm,

or as high as 400mm in high rise buildings. Shear walls

are usually provided along both length and width of

buildings. Shear walls are like vertically-oriented wide

beams that carry earthquake loads downwards to the

foundation. Properly designed and detailed buildings with

shear walls have shown very good performance in past

earthquakes.

In India 60% of geographical area comes in earthquake

zone 3, 4 and 5. So use of shear wall structures has

become popular in buildings up to 70 storeys. Shear walls

in high seismic regions require special detailing.

However, in past earthquakes, even buildings with

sufficient amount of walls that were not specially detailed

for seismic performance (but had enough well-distributed

reinforcement) were saved from collapse. Shear walls are

easy to construct, because reinforcement detailing of walls

is relatively straight-forward and therefore easily

implemented at site. Shear walls are efficient, both in

terms of construction cost and effectiveness in minimizing

earthquake damage in structural and non-structural




elements (like glass windows and building contents.)

Since shear walls carry large horizontal earthquake forces,

the overturning effects on them are large. Thus, design of

their foundations requires special attention.

A. Pattern of shear wall

Different geometries are possible. Shear walls are

oblong in cross-section, i.e., one dimension of the cross-

section is much larger than the other. While rectangular

cross-section is common, L and U shaped sections are

also used. Thin-walled hollow RC shafts around the

elevator core of buildings also act as shear walls. If the

shear wall locates on plan unsymmetrical then there are

increased chances of torsion besides shear force and

bending moment. Walls are connected by floor slabs or

beams which are assumed to have negligible bending

resistance.

Fig3. Shear wall typical sections.

B. Location of Shear wall

Shear walls in buildings must be symmetrically located

in plan to reduce ill-effects of twist in buildings. They

could be placed symmetrically along one or both

directions in plan. Individual wall may be subjected to

axial, translational, and torsional displacements. The

extent to which a wall will contribute to the resistance of

overturning moments, storey forces, and storey torsion

depends on its geometric configuration, orientation and

location within the plane of the building. Position of shear

wall is usually dictated by functional requirements. These

may or may not suit structural planning. Under the large

overturning effects caused by horizontal earthquake

forces, edges of shear walls experience high compressive

and tensile stresses. To ensure that shear walls behave in a

ductile way, concrete in the wall end regions must be

reinforced in a special manner to sustain these load

reversals without losing strength. Sometimes, the

thickness of the shear wall in these boundary elements is

also increased. RC walls with boundary elements have

substantially higher bending strength and horizontal shear

force carrying capacity, and are therefore less susceptible

to earthquake damage than walls without boundary

elements.

Fig4. Shear wall plan layout(adapted from earthquake

tips)

IV. RESULTS

A. Combined footing

Whenever two or more columns in a straight line are

carried on a single spread footing, it is called a combined

footing. Isolated footings for each column are generally

the economical. Combined footings are provided only

when it is absolutely necessary, as When two columns are

close together, causing overlap of adjacent isolated

footings Where soil bearing capacity is low, causing

overlap of adjacent isolated footings Proximity of building

line or existing building or sewer, adjacent to a building

column.

Fig5. Combined Footing with Loads.

B. Types of Combined Footing

The combined footing may be rectangular,

trapezoidal or Tee-shaped in plan.

The geometric proportions and shape are so fixed that

the centeroid of the footing area coincides with the

resultant of the column loads. This results in uniform




pressure below the entire area of footing.

Trapezoidal footing is provided when one column

load is much more than the other. As a result, the both

projections of footing beyond the faces of the

columns will be restricted.

Rectangular footing is provided when one of the

projections of the footing is restricted or the width of

the footing is restricted.

Longitudinally, the footing acts as an upward loaded

beam spanning between columns and cantilevering

beyond. Using statics, the shear force and bending

moment diagrams in the longitudinal direction are

drawn. Moment is checked at the faces of the column.

Shear force is critical at distance ‘d’ from the faces of

columns or at the point of contra flexure. Two-way

shear is checked under the heavier column.

The footing is also subjected to transverse bending

and this bending is spread over a transverse strip near

the column.

Fig6. Types of Combined Footing.

Fig7. Critical Sections for Moments and Shear.

C. Design Steps

Locate the point of application of the column loads on the

footing. Proportion the footing such that the resultant of

loads passes through the center of footing. Compute the area

of footing such that the allowable soil pressure is not

exceeded. Calculate the shear forces and bending moments

at the salient points and hence draw SFD and BMD. Fix the

depth of footing from the maximum bending moment.

Calculate the transverse bending moment and design the

transverse section for depth and reinforcement. Check for

anchorage and shear. Check the footing for longitudinal

shear and hence design the longitudinal steel Design the

reinforcement for the longitudinal moment and place them in

the appropriate positions. Check the development length for

longitudinal steel Curtail the longitudinal bars for economy

Draw and detail the reinforcement Prepare the bar bending

schedule.

Table3.

Table4.

Foundation:

Table5




Based on spacing reinforcement increment; provided

reinforcement is Ø12 @ 185 mm o.c.




V. CONCLUSION AND FUTURE WORK

This study deals with the analytical investigation of a

structure subjected to gravity and lateral loads. Based on

the results and comparisons the following conclusions are

drawn Placement of shear wall inside mid greatly resisted

by lateral loads other than shear wall. All the types of

buildings whose length is same in X & Y direction,

placing the shear wall would give the best resistant to

lateral loads.

Future Scope of Study : Cost comparison Placing right

position of shear wall in unsymmetrical building to resist

maximum lateral force. Analysis with constructing wall

on beams with specific wall bond type and wall prismatic

compressive strength is required.

VI. REFERENCES

[1] IS 1893-2002 Criteria for Earthquake Resistant Design

of Structures Part 1 General Provisions and Buildings.

[2] Earthquake tips, C.V.R. MURTY

[3] IS 875 Code of practice for design loads (other than

earthquake) for buildings and structure

[4] IS 13920, (1993), “Indian Standard Code of Practice

for Ductile Detailing of Reinforced Concrete Structures

Subjected to Seismic Forces”.

[5] Staad .pro manual.

Shear Wall Design of A G+2 Structure in STAAD Pro

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