Design of Special Structural Shear Wall - Compressive Stress Approach (ACI 318-19)
When properly proportioned so that they possess adequate lateral stiffness to reduce interstory distortions due to earthquake-induced motions, structural walls (also called shear walls) reduce the likelihood of damage to the nonstructural elements of a building. Structural walls are normally much stiffer than regular frame elements and are therefore subjected to correspondingly greater lateral forces due to earthquake motions. Because of their relatively greater depth, the lateral deformation capacities of walls are limited, so that, for a given amount of lateral displacement, structural walls tend to exhibit greater apparent distress than frame members. However, over a broad period range, a structure with structural walls, which is substantially stiffer and hence has a shorter period than a structure with frames, will suffer less lateral displacement than the frame, when subjected to the same ground motion intensity. Structural walls with a height-to-horizontal length ratio, hw/lw, in excess of 2 behave essentially as vertical cantilever beams and should therefore be designed as flexural members, with their strength governed by flexure rather than by shear. Special reinforced concrete structural shear walls are required in structures assigned to Seismic Design Category (SDC) D or higher. This example illustrates the design procedure and steps of a special structural shear wall in the first story of a 30-story building providing lateral and gravity load resistance for the factored loads shown in the “Design Data” section. This example will conclude with a comparison of the calculated results with the exact values obtained from the spColumn engineering software program from StructurePoint is also provided.
Figure 1 - Wall Cross-Section