Analysis and Design of Shear Wall

8/13/2019 Analysis and Design of Shear Wall

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For a structural engineer a tall building can be defined asone whose structural system must be modified to make itsufficiently economical to resist lateral forces due to windor earthquakes within the prescribed criteria for strength,

drift and comfort of the occupants. High land prices, limitations of its availability, transport

problems and in-creasing availability of energy, advancein technology and communications among otherbetween them, are moving the society to grow vertical.

Between 1940 and 1950 shear walls were introduced asan economical efficient bracing system for multistoriedbuildings.


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Traditionally, the primary concern of the structural

engineer designing a building has been the provision of

a structurally safe and adequate system to support

vertical loads

. The effect of lateral loads like wind loads, earthquakeforce and blast force etc., are attaining increasing

importance and almost every designer is faced with the

problem of providing adequate strength and stability

against lateral loads.


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The buildings are subjected to both vertical and

horizontal loads.

Ideally an efficient system should not require an increase

in the sizes of members when the effect of lateral loads

is also incorporated('Premium free design).

Horizontal loads can be divided into the following three

categories: -

(I) Wind loads

(ii) Earthquake loads, and

(iii) Blast loads.


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The structural requirements are: -(a) Strength

(b) Stiffness(c) Stability

The functional requirements are:-

To prevent non-structural damage in frequent minor ground

shaking

To prevent structural damage and minimize non-structuraldamage in occasional moderate ground shaking

To avoid collapse or serious damage in rare major ground

shaking


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Shear walls provide large strength and stiffness to

buildings in the direction of their orientation.

shear walls carry large horizontal earthquake forces, the

overturning effects on them are large.

Shear walls should be provided along preferably both

length and width.

Door or window openings can be provided in shear

walls, but their size must be small to ensure least

interruption to force flow through walls.

Shear walls in buildings must be symmetrically located in

plan to reduce ill-effects of twist in buildings.


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Simple rectangular types and flanged walls(bar

bell type)

Coupled shear walls

Rigid frame shear walls

Framed walls with in filled frames

Column supported shear walls

Core type shear walls


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Shear walls, in particular, must be strong in themselvesand also strongly connected to each other and to thehorizontal diaphragms.

In a simple building with shear walls at each end, ground

motion enters the building and creates inertial forces thatmove the floor diaphragms.

This movement is resisted by the shear walls and theforces are transmitted back down to the foundation.

While designing the walls a balance must be found in theratio of vertical load and ductility.

The possibility of any of the modes of failure occurringcan be minimized by increasing the vertical load on thewall.


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As shear walls act primarily as cantilevers they have three

basic failure modes.


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The stiffness of the shear wall, just like its strength,

depends on the combined stiffness of its components.

Shear walls provide stiffness in large part by the ratio oftheir height to width.

Long short walls are stiffer than tall narrow ones.

For a wall of constant height, the stiffness will grow

exponentially as the wall length increases.


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Properly designed and detailed buildings with shear

walls have shown very good performance in past

earthquakes.

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.


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Japanese concrete shear-wall apartment

buildings after the 1964 M 7.2 Niigata

earthquake. Despite the fact that the

foundations of the buildings failed due toliquefaction, the building structures were

undamaged and the buildings were later

jacked back to an upright position and they

were reoccupied.

Shear core used in multi-storey structure

(NZ).


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Millikan Library, a 9 story building in

Pasadena, CA, USA

El Castillo Building in Mayaguez, Puerto Rico. 19story, 2

basement concrete shear wall structure


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Murthy, C.V.R. (2004), Earthquake tip 23, IITK-bmtpc Earthquake

tips, IIT Kanpur, India.

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

Structures, BIS, New Delhi

IS 13920: 1993 code of practice for Ductile detailing of reinforcedconcrete structures subjected to seismic forces.

P.C.Varghese, Advanced Reinforced Concrete Design, Prentice-

Hall of India Private Limited, New Delhi, 2001 .

Paulay,T. and Priestley, M.J.N (1992) , Seismic design of reinforced

concrete and masonry buildings. Farzad Naeim, Theseismic design handbook,Chapman and Hall,

New York-1999.

J. N. Bandyopadhyay,Earthquake Resistant Design and Detailing of

RCC structures as per codal provisions, chapter 17-SE 106

NPCBEERM, MHA (DM).


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Analysis and Design of Shear Wall