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Seismic Behaviour of RC Shear Walls MAHDI HOSSEINI

1, AHMED NAJM ABDULLAH AL-ASKARI

2, PROF, N.V. RAMANA RAO

3

1PG Scholar, Dept of Civil Engineering, JNTUH, Hyderabad, India, E-mail: [email protected].

2PG Scholar, Dept of Civil Engineering, JNTUH, Hyderabad, India & Ministry of Municipalities &

Public Works, Iraq, E-mail: [email protected]. 3Professor, Dept of Civil Engineering, JNTUH, Hyderabad, India, E-mail: [email protected].

Abstract: Shear walls are a type of structural system that provides lateral resistance to a building or structure. They 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. The performance of the framed buildings depends on the structural system adopted for the structure The

term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The

structural system transfers loads through interconnected structural components or members. These structural systems need to be

chosen based on its height and loads and need to be carried out, etc. The selection of appropriate structural systems for building

must satisfy both strength and stiffness requirements. The structural system must be adequate to resist lateral and gravity loads

that cause horizontal shear deformation and overturning deformation. Other important issues that must be considered in

planning the structural schemes and layouts are the requirements for architectural details, building services like vertical

transportation and fire safety among others. Each of the structural system will be having its own prospects and considerations.

The efficiency of a structural system is measured in terms of their ability to resist lateral load, which increases with the height

of the frame. A building can be considered as tall when the effect of lateral loads is reflected in the design. Lateral deflections

of framed buildings should be limited to prevent damage to both structural and nonstructural elements.

Keywords: RC Structure, Seismic Load ,Wind Load, RC Shear Wall, Structural System.

I. INTRODUCTION

A. What Causes Lateral Loads?

Lateral loads result from wind or earthquake actions and

both can cause a collapse of improperly braced building. The

way that wind or earthquake loads act on a building is

completely different, but they have the same general effect.

These two sources of lateral load are discussed below.

B. Wind Load

Wind load is really the result of wind pressures acting on

the building surfaces during a wind event. This wind pressure

is primarily a function of the wind speed because the pressure

or load increases with the square of the wind velocity (i.e.,

doubling of wind speed results in a four-fold increase in wind

load or pressure). Wind load during a hurricane can last hours

and a building experiences sustained wind load and short

wind impacts (gusts). While the wind pressures are treated as

a “static” (do not vary with time) or constant load for

purposes of design, the real loads actually fluctuate

dramatically with gustiness of wind as well as wind direction.

Two fundamental wind effects are of a concern: (1) localized

“spikes” in wind pressure that act on small areas of a building

to cause damage to items such as roof panels or siding

(known as components and cladding wind loads in

engineering terms) and (2) averaged wind loads that act on

larger areas of the building which the entire structure must

resist(known in engineering terms as main wind force

resisting system loads).

C. Earthquake Load

Earthquake forces experienced by a building result from

ground motions (accelerations) which are also fluctuating or

dynamic in nature, in fact they reverse direction somewhat

chaotically. The magnitude of an earthquake force depends

on the magnitude of an earthquake, distance from the

earthquake source(epicenter), local ground conditions that

may amplify ground shaking (or dampen it), the weight(or

mass) of the structure, and the type of structural system and

its ability to with stand abusive cyclic loading. In theory and

practice, the lateral force that a building experiences from an

earthquake increases in direct proportion with the

acceleration of ground motion at the building site and the

mass of the building (i.e., a doubling in ground motion

acceleration or building mass will double the load).This

theory rests on the simplicity and validity of Newton’s law of

physics: F = m x a, where ‘F’ represents force, ‘m’ represents

mass or weight, and ‘a’ represents acceleration. For example,

as a car accelerates forward, a force is imparted to the driver

through the seat to push him forward with the car(this force is

equivalent to the weight of the driver multiplied by the

http://en.wikipedia.org/wiki/Structural_system

http://en.wikipedia.org/wiki/Plane_(mathematics)

http://en.wikipedia.org/wiki/Diaphragm_(structural_system)

http://en.wikipedia.org/wiki/Drag_(physics)

http://en.wikipedia.org/wiki/Structural_engineering

http://en.wikipedia.org/wiki/Structural_load

http://en.wikipedia.org/wiki/Sub-system

http://en.wikipedia.org/wiki/Structural_load

http://en.wikipedia.org/wiki/List_of_structural_elements

MAHDI HOSSEINI, AHMED NAJM ABDULLAH AL-ASKARI, PROF, N.V. RAMANA RAO

International Journal of Scientific Engineering and Technology Research

Volume.03, IssueNo.18, August-2014, Pages: 3878-3886

acceleration or rate of change in speed of the car). As the

brake is applied, the car is decelerated and a force is imparted

to the driver by the seat-belt to push him back toward the

seat. Similarly, as the ground accelerates back and forth

during an earthquake it imparts back-and-forth(cyclic) forces

to a building through its foundation which is forced to move

with the ground. One can imagine a very light structure such

as fabric tent that will be undamaged in almost any

earthquake but it will not survive high wind. The reason is

the low mass (weight) of the tent. Therefore, residential

buildings generally perform reasonably well in earthquakes

but are more vulnerable in high-wind load prone areas.

Regardless, the proper amount of bracing is required in both

cases.

D. What parts of a structure resist lateral loads?

The lateral resistance of the residential structure is almost

entirely provided by a system of shear walls and diaphragms.

These two parts of the lateral force resisting system (bracing

system) of a home are discussed below.

Fig1. Concept of shear walls and diaphragms. All walls

contribute to the house stiffness.(a) Schematic, (b) Wall

participation is the force transfer.

1. Diaphragm

A diaphragm is a structural term that simply refers to a

horizontal plate-like system (i.e., a sheathed floor, ceiling or

a roof assembly) that distributes lateral loads acting on the

building to shear walls (or braced wall lines) that support a

floor or roof diaphragm and prevent it from excessive

sideways movement leading to potential collapse. Thus, a

floor or roof diaphragm serves an important role of tying the

light-frame building together (Figure 1). The basic concept is

to collect all the loads and transfer them to the foundation. In

the IRC, construction of floor and roof systems (diaphragms)

is addressed in separate chapters of the code (Chapters 5 and

8)

2. Shear Wall

A shear wall is a structural term for a wall or portion of a

wall line (i.e., braced wall panel) that is specifically braced to

prevent racking of the studs in domino fashion as the floor or

roof diaphragm above transfers shear (racking) forces into

the plane (length direction) of a braced wall line (braced wall

line is explained latter in the text). In general, only braced

wall lines parallel to a given lateral load direction are

considered in providing racking resistance. However, even

the interior and transverse walls (Figure 1b) participate in

load transfer and overall stiffness providing that they too are

adequately connected to the floor or roof diaphragm system

above. This three-dimensional action is not explicitly

considered in the current IRC bracing provisions and requires

the services of a design professional to implement. In

addition, the portion of the lateral load imparted to each shear

wall or braced wall line by a floor or roof diaphragm depends

on various factors but, in general, a stiffer wall (stronger and

more rigid bracing) will attract a larger portion of the total

lateral load as compared to the less stiff wall (3). Unlike

water, structural loads tend to follow the path of greatest

resistance or stiffness until that path is “broken” or

weakened.

Fig2. Schematic of the deformations of the structure due

to the lateral loads.

This means, for example, that a wall with large opening

will attract fewer loads compared to a wall of the same size

and construction with small or no opening. As discussed

above, “wall bracing” is an important part of the bracing

system but will not, by itself, be sufficient in providing

lateral resistance of the building. An entire system and load

path must be established (e.g., diaphragms connected to shear

walls, shear walls connected to floors/foundation, etc.).

Consequently, the IRC provides basic connection

requirements for framing (floor, wall, and roof construction)

to provide such a system for the limited design wind and

earthquake conditions addressed directly in the code. For

extremely hazards areas (hurricane-prone regions) and near

fault areas in seismic zones, an engineered design is required.

Alternatively, a prescriptive design in accordance with

reference standards in Section R301 of the IRC may be used.

In Pennsylvania, such high hazard wind or seismic conditions

do not exist. When a building is subjected to wind or

earthquake load, various types of failure must be prevented:

Seismic Behaviour of RC Shear Walls



Slipping off the foundation (sliding)

Overturning and uplift (anchorage failure)

Shear distortion (drift or racking deflection)

Collapse (excessive racking deflection)

The first three types of failure are schematically shown in

the Figure2 Clearly, the entire system must be tied together to

prevent building collapse or significant deformation.

II. METHODOLOGY WHY ARE BUILDINGS WITH

SHEAR WALLS PREFERRED IN SEISMIC ZONES? Generally shear wall can be defined as structural vertical

member that is able to resist combination of shear, moment

and axial load induced by lateral load and gravity load

transfer to the wall from other structural member. Reinforced

concrete walls, which include lift wells or shear walls, are the

usual requirements of Multi Storey Buildings. Design by

coinciding centroid and mass center of the building is the

ideal for a Structure. An introduction of shear wall represents

a structurally efficient solution to stiffen a building structural

system because the main function of a shear wall is to

increase the rigidity for lateral load resistance. In modern tall

buildings, shear walls are commonly used as a vertical

structural element for resisting the lateral loads that may be

induced by the effect of wind and earthquakes which cause

the failure of structure as shown in figure Shear walls of

varying cross sections i.e. rectangular shapes to more

irregular cores such as channel, T, L, barbell shape, box etc.

can be used. Provision of walls helps to divide an enclose

space, whereas of cores to contain and convey services such

as elevator. The use of shear wall structure has gained

popularity in high rise building structure, especially in the

construction of service apartment or office/ commercial

tower. It has been proven that this system provides efficient

structural system for multi storey building in the range of 30-

35 storey’s (MARSONO & SUBEDI, 2000). In the past 30

years of the record service history of tall building containing

shear wall element, none has collapsed during strong winds

and earthquakes (FINTEL, 1995).

A. RC Shear Wall

Reinforced concrete (RC) buildings often have vertical

plate-like RC walls called Shear Walls in addition to slabs,

beams and columns. 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. The overwhelming 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.” as said by Mark Fintel, a noted consulting

engineer in USA. RC shear walls provide large strength and

stiffness to buildings in the direction of their orientation,

which significantly reduces lateral sway of the building and

thereby reduces damage to structure and its contents. Since

shear walls carry large horizontal earthquake forces, the

overturning effects on them are large. 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. Shear

walls are more effective when located along exterior

perimeter of the building such a layout increases resistance of

the building to twisting.

B. Function of Shear Wall

Shear walls must provide the necessary lateral strength to

resist horizontal earthquake forces. When shear walls are

strong enough, they will transfer these horizontal forces to

the next element in the load path below them Shear walls also

provide lateral stiffness to prevent the roof or floor above

from excessive sides way. When shear walls are stiff enough,

they will prevent floor and roof framing members from

moving off their supports. Also, buildings that are

sufficiently stiff will usually suffer less nonstructural

damage. Reinforced concrete building structures can be

classified as:

1. Structural Frame Systems: The structural system consist

of frames. Floor slabs, beams and columns are the basic

elements of the structural system. Such frames can carry

gravity loads while providing adequate stiffness.

2. Structural Wall Systems: In this type of structures, all the

vertical members are made of structural walls, generally

called shear walls.

3. Shear Wall–Frame Systems (Dual Systems): The system

consists of reinforced concrete frames interacting with

reinforced concrete shear walls.

In the lateral load analysis of building structures having

shear walls, proper methods should be used for modeling

planar and no planar shear wall assemblies. Shear wall

models in the literature can be divided into two:

1. Models developed for elastic analysis of building

structures.

2. Models developed for nonlinear analysis of building

structures.

C. Shear Walls: Stiffness

Deflection calculations shall be based on cracked section

properties. Assumed properties shall not exceed half of gross

section properties, unless a cracked-section analysis is

performed.




Real wall is probably between two cases; diaphragm provides

some Shear Walls 9 rotational restraint, but not full fixity.

D. Maximum reinforcing

No limits on maximum reinforcing for following case

Reinforcement limits: Calculated using Maximum stress in

steel of fy Axial forces taken from load combination

D+0.75L+0.525QE Compression reinforcement, with or

without lateral ties, permitted to be included for calculation

of maximum flexural tensile reinforcement

Fig1.




III.SEISMIC BEHAVIOUR OF SHEAR WALL










IV. CONCLUSIONS

Properly designed and detailed buildings with shear walls

have shown very good performance in past earthquakes. The

overwhelming 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. 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 wall buildings are a popular choice in many

earthquake prone countries, like Chile, New Zealand and

USA. 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 properly designed

and detailed buildings with Shear walls have shown very

good performance in past earthquakes. The overwhelming

success of buildings with shear walls in resisting strong

earthquakes is summarized in the quote: And effectiveness in

minimizing earthquake damage in structural and non-

Structural elements (like glass windows and building

contents).

V. REFERENCES

[1] Solution of shear wall in multi-storey building”,

Anshuman, Dipendu Bhunia, Bhavin Ramjiyani,

International journal of civil and structural engineering,

Volume 2, no.2, 2011.

[2] “Review on Shear wall for soft storey high rise building,

Misam Abidi and Mangulkar Madhuri N. ,International

Journal of Civil and Advance Technology, ISSN 2249-

8958,Volume-1,Issue-6, August 2012

[3] “Effect of change in shear wall location on storey drift of

multi-storey residential building subjected to lateral load”,

Ashish S. Agrawal and S. D. Charkha, International journal

of Engineering Research and Applications, Volume 2, Issue

3,may-june 2012, pp.1786-1793.

[4] “Configuration of multi-storey building subjected to

lateral forces”, M Ashraf, Z. A. Siddiqui, M. A. Javed, Asian

journal of civil engineering ,vol. 9,no.5, pp. 525-535, 2008.

[5] Y. L. Mo and C. J. Kuo. 1998. Structural behavior of

reinforced concrete frame-wall components, department of

civil engineering, national Cheng kung University, Tainan,

701, Taiwan.

[6] Chen Qin and Qian Jiaru .2002.Sstatic inelastic analysis

of RC shear walls, department of civil engineering, Tsinghua

University, Beijing 100084, China. Article ID: 1671-

3664(2002) 01-0094-06.

[7] Y. L. Mo and S.D. Jost .1993.Seismic response of

multistory framed shear walls, department of Civil

Engineering, National Cheng Kung University, Taiwan

70101, Taiwan.

[8] Arnaldo T. Derecho and M. Reza Kianoush, seismic

Design of reinforced concrete structures, Professor, Ryerson

Polytechnic University, Ontario, Canada.

[9] Taranath, B. S., Structural Analysis and Design of Tall

Buildings, McGraw-Hill Company, 1988.

[10] Öztorun, N. K., “Computer Analysis of Multi-Storey

Building Structures”, Ph.D. Thesis, Middle East Technical

University, 1994.

[11] “Response of Buildings to Lateral Forces”, ACI

Committee Report, SP-97, American Concrete Institute,

Detroit, 1985: 21-46.

Author’s Profile:

Mahdi Hosseini, Post Graduate

Student, Dept. of Civil Engineering,

Jawaharlal Nehru Technological

University Hyderabad (JNTUH),

Hyderabad, Andhra Pradesh, India.

Email: [email protected].

Ahmed Najm Abdullah Al-Askari,

Ministry of Municipalities and Public

Works-IRAQ, Post Graduate Student,

Dept. of Civil Engineering, Jawaharlal

Nehru Technological University

Hyderabad (JNTUH), Hyderabad,

Andhra Pradesh, India.

Email: [email protected],

[email protected].

mailto:[email protected]






Prof.N.V.Ramana Rao, Professor,

Dept. of Civil Engineering, Jawaharlal

Nehru Technological University

Hyderabad (JNTUH), Hyderabad,

Andhra Pradesh, India.

Email: [email protected].

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