Tensile forces for seismic design of braced frame connections — Experimental results

Experimental results from seventeen large scale tests on bracing members are presented within the context of tensile force demands on connections during seismic loading. The bracing members are subjected to three cyclic loading histories consistent with expected axial deformation demands during seismic loading in concentrically braced frames. The experiments feature commonly used cross-sections including HSS, Pipe and Wide-flanged beams. The test data suggests that the current approach of designing bracing connections based on the expected yield strength of the brace is somewhat unconservative, since it does not incorporate the effect of strain hardening. This trend is observed across all the cross-section types and loading histories. On average, the current approach underestimates the maximum forces transferred to connections by 9%–11%, depending on the level of deformation expected in the brace. To reduce this unconservatism, an alternate approach, based on the average of the expected yield and ultimate strength is proposed. This approach provides significantly improved estimates of the forces that may be transferred to bracing connections. Limitations of the study and future work are outlined.