Shear Walls Design Review

 
In structural engineering, a shear wall is a wall composed of braced panels (also known as shear panels) to counter the effects of lateral load acting on a structure. Wind and earthquake loads are the most common loads braced wall lines are designed to counteract. Under several building codes, including the International Building Code (where it is called a braced wall line) and Uniform Building Code, all exterior wall lines in wood or steel frame construction must be braced. Depending on the size of the building some interior walls must be braced as well.
 
Walls subject to horizontal shear forces in the plane of the wall should, in addition to satisfying flexural requirements, be capable of resisting the shear. The nominal shear stress can be computed from:
 
 
This equation does not apply, however, when Mu/Vu - lw/2 is negative.
 
When the factored shear Vu is less than 0.5Vc, reinforcement should be provided as required by the empirical method for bearing walls.
 
When Vu exceeds 0.5Vc, horizontal reinforcement should be provided with:
 
 Vs = Av fyd/s2
 
where s2 = spacing of horizontal reinforcement, and Av = reinforcement area. Also, the ratio ph of horizontal shear reinforcement, to the gross concrete area of the vertical section of the wall should be at least 0.0025. Spacing of horizontal shear bars should not exceed lw/5, 3h, or 18 in (457.2 mm). In addition, the ratio of vertical shear reinforcement area to gross concrete area of the horizontal section of wall does not need to be greater than that required for horizontal reinforcement but should not be less than:
 
 
where hw = total height of wall. Spacing of vertical shear reinforcement should not exceed lw/3, 3h, or 18 in (457.2 mm).
 
In no case should the shear strength Vn be taken greater than:
 
 
at any section.
 
Bearing stress on the concrete from anchorages of posttensioned members with adequate reinforcement in the end region should not exceed fb calculated from:
 
 
where Ab = bearing area of anchor plate, and Ab' maximum area of portion of anchorage surface geometrically similar to and concentric with area of anchor plate.
 
A more refined analysis may be applied in the design of the end-anchorage regions of prestressed members to develop the ultimate strength of the tendons.   should be taken as 0.90 for the concrete.
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