## 308 Design Charts

Research, testing, and applications have progressed to the point where tubular connections are about as reliable as the other structural elements with which designers deal. One of the principal barriers to more widespread use seems to be unfamiliarity. To alleviate this problem, design charts for connections of circular tubes have been presented by Marshall [10]. Packer's original charts for square and rectangular tubes appear in the AISC Manual.

The capacity of simple, direct, welded, tubular connections are given in terms of punching shear efficiency, Ev, where allowable punching shear stress main member allowable tension stress

Charts for punching shear efficiency for axial load, in-plane bending, and out-of-plane bending appear as Figure 30.5 to Figure 30.9. Note that for axial load, separate charts are given for K connections, T/Y connections, and X connections, reflecting their different load patterns and different values of the ovalizing parameter (alpha). Within each connection or load type, punching shear efficiency is a function of the geometry parameters, diameter ratio (beta), and chord radius or thickness (gamma), as defined earlier. For K connections, the gap, g, between braces (of diameter d ) is also significant, with the behavior reverting to that of T/Y connections for a very large gap. Punching shear efficiency cannot exceed a value of 0.4Fyo/0.6Fy = 0.67, the material limit for shear.

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