Another example of deflection incompatibility is with a wall under wind load. This is particularly true of cold formed steel (CFS) framing. Wood framing is usually overdesigned by default.
Consider a wall under lateral wind load with one or more windows in the wall. The corners of the wall are restrained by shear resistance, either through a 90 degree wall return or by termination of the wall into something more substantial such as a masonry or cast-in-place concrete intersection.
The studs for the wall are designed for stress, with only minor consideration for deflection, since that is moreso a serviceability issue. In an effort to create fewer problems for the contractor, the designer uses the same size/configuration/Section properties of the studs across the wall. When you get to a window opening, there is at least a doubling of the studs on either side of the window, sometimes a tripling or quadrupling of the studs considering the size and loading on the window.
Now consider that the face cladding on the wall is a rigid material such as stucco. Stucco has a typical maximum deflection criterion of L/360. This is commonly checked in one direction for the studs (individually), but is often not considered for the condition where the window framing creates a "hard spot" in the wall and the wall bends in two directions, not just one as the deflection check implies. The result is lack of consideration that bending occurs in the wall in a diaphragmatic condition, not just linearly as was checked. This leads to more potential for stucco cracking, water intrusion, and deterioration of the walls from this lack of appropriate consideration of deflection incompatibility. Leads to many thousands, perhaps millions, of dollars in damage to the structure.
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