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IITK-BMTPC Earthquake Tip 23

Why are Buildings with Shear Walls preferred in Seismic Regions? page 2
Ductile Design of Shear Walls increased. RC walls with boundary elements have
Just like reinforced concrete (RC) beams and substantially higher bending strength and horizontal
columns, RC shear walls also perform much better if shear force carrying capacity, and are therefore less
designed to be ductile. Overall geometric proportions susceptible to earthquake damage than walls without
of the wall, types and amount of reinforcement, and boundary elements.
connection with remaining elements in the building
help in improving the ductility of walls. The Indian

Standard Ductile Detailing Code for RC members Tension Compression
(IS:13920-1993) provides special design guidelines for
ductile detailing of shear walls.
Overall Geometry of Walls: Shear walls are
Closely spaced confining
oblong in cross-section, i.e., one dimension of the reinforcement in boundary
cross-section is much larger than the other. While elements

rectangular cross-section is common, L- and U-shaped Proper anchoring of vertical

sections are also used (Figure 3). Thin-walled hollow reinforcement into foundation
RC shafts around the elevator core of buildings also
act as shear walls, and should be taken advantage of to
resist earthquake forces. (a)

C-Shaped
L-Shaped Boundary Boundary Elements
Element without increased thickness

Boundary Elements Boundary
with increased thickness Element

RC Hollow
Core around

Elevators Confining reinforcement in
Anchoring of wall

reinforcement in
boundary elements: boundary element
135° hooks, closely spaced ties
Rectangular (b)

Figure 3: Shear walls in RC Buildings – different Figure 4: Layout of main reinforcement in shear

walls as per IS:13920-1993 – detailing is the
geometries are possible. key to good seismic performance.
Reinforcement Bars in RC Walls: Steel
reinforcing bars are to be provided in walls in
regularly spaced vertical and horizontal grids (Figure Related - Earthquake Tip
4a). The vertical and horizontal reinforcement in the Tip 6: How Architectural Features Affect Buildings During
Earthquakes?
wall can be placed in one or two parallel layers called Tip 19: How do Columns in RC Buildings Resist Earthquakes?
curtains. Horizontal reinforcement needs to be
anchored at the ends of walls. The minimum area of Reading Material
reinforcing steel to be provided is 0.0025 times the IS 13920, (1993), “Indian Standard Code of Practice for Ductile Detailing
cross-sectional area, along each of the horizontal and of Reinforced Concrete Structures Subjected to Seismic Forces,” Bureau
of Indian Standards, New Delhi
vertical directions. This vertical reinforcement should Paulay,T., and Priestley,M.J.N., (1992), “Seismic Design of Reinforced
be distributed uniformly across the wall cross-section. Concrete and Masonry Buildings,” John Wiley & Sons, USA
Boundary Elements: Under the large overturning
effects caused by horizontal earthquake forces, edges Authored by:
of shear walls experience high compressive and tensile C.V.R.Murty
stresses. To ensure that shear walls behave in a ductile Indian Institute of Technology Kanpur
way, concrete in the wall end regions must be Kanpur, India
reinforced in a special manner to sustain these load Sponsored by:
reversals without loosing strength (Figure 4b). End Building Materials and Technology Promotion
regions of a wall with increased confinement are called Council, New Delhi, India
boundary elements. This special confining transverse
reinforcement in boundary elements is similar to that This release is a property of IIT Kanpur and BMTPC New
provided in columns of RC frames (See IITK-BMTPC Delhi. It may be reproduced without changing its contents
and with due acknowledgement. Suggestions/comments
Earthquake Tip 19). Sometimes, the thickness of the may be sent to: nicee@iitk.ac.in Visit www.nicee.org or
shear wall in these boundary elements is also www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips.

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