Since the lateral loads are resisted by the truss diagonals, there is no bending of columns in the transverse direction. Thus, the columns are typically oriented with their weak axis perpendicular to the longitudinal direction of the building. Consequently, the weak-axis bending of columns due to gravity deflection of trusses must be considered in designing columns. This effect can, however, be minimized by introducing a camber in the truss by

Figure 3.13. Conceptual two-dimensional model for staggered truss system: (a, b) lateral deformation of adjacent bays; (c) overall behavior. Note the absence of local bending of columns.

deliberately making the truss bottom chord shorter than the top chord. An alternate solution is to design the connection between the truss bottom chord and column as a slip connection for dead loads. The bolts may then be torqued after the application of dead loads, thus limiting the bending moments in the columns due to truss deflections. If neither of these two methods is applicable, then the moments in columns due to the deflection of truss must be provided for in the design.

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