Shear walls

A shear wall is a reinforced concrete wall that resists lateral load by acting as a deep vertical cantilever fixed at the foundation. Because its stiffness in its own plane is far greater than that of a column, a few well-placed walls can control the drift of a building in wind and earthquakes and keep partitions, services and the occupants safe.

Under lateral load, a slender wall bends: one edge goes into tension and the other into compression, and shear runs through the web. Vertical reinforcement resists the bending tension, horizontal reinforcement resists shear, and both are distributed in two curtains in walls of normal thickness. At the edges, where compression is highest, boundary elements with closely spaced confining hoops prevent crushing and bar buckling. Openings for doors and windows turn a solid wall into coupled walls linked by short deep beams, which need diagonal reinforcement to work as fuses.

Placement matters as much as strength. Walls arranged symmetrically in plan, preferably near the perimeter, resist torsion; a single wall core on one side causes the building to twist. Walls should run continuously from the foundation to the top; stopping a wall at the first floor to open up a lobby creates a dangerous discontinuity.

Foundations of shear walls see large overturning moments and need a raft, piles or a heavy combined footing. In analysis, cracked-section stiffness is used for drift checks. Indian rules for ductile walls are in IS 13920, with overall seismic design in IS 1893.