Shear Walls

Cantilevered shear walls used for bracing structures against lateral displacement (sidesway) are a special case of deep beams. They may be used as the only lateral bracing, or in conjunction with beam-column frames. In the latter case, the lateral displacement of the combination can be calculated with the assumption that lateral forces resisted by each element can be distributed to walls and frames in proportion to stiffness. For tall structures, the effect of axial shortening of the frames and the contribution of shear to lateral deformation of the shear wall should not be neglected.
Figure 9.56 indicates the forces assumed to be acting on a horizontal cross section of a shear wall.

Reinforcement required for flexure of shear walls as a cantilever should be proportioned as for deep beams (Art. 9.88). Shear reinforcement is usually furnished as a combination of horizontal and vertical bars distributed evenly in each story (for increment of load). For low shear (where the factored shear force Vu at a section is less than 0.5Vc, where Vc is the nominal shear permitted on the concrete), the minimum shear reinforcement required and its location in a wall are the same as for bearing walls (Art. 9.68). Maximum spacing of horizontal shear reinforcement, however, should not exceed Lw/5, 3h, or 18 in, where Lw is the horizontal length of wall and h the overall wall thickness (Fig. 9.56). Maximum spacing of the vertical reinforcement should not exceed Lw/3, 3h, or 18 in.

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