Inelastic Buckling of Steel Struts under Cyclic Load Reversals

摘要

Cyclic axial loading experiments simulating severe seismic conditions are described for twenty-four structural steel struts of sizes and shapes typically employed as braces in small to moderately large steel buildings. The cross-sectional geometries of the specimens were also chosen to model the larger, heavier struts. Six of the twenty-four members were pinned at one end and fixed at the other, while the remaining eighteen were pinned at both ends. The range of cross-sectional shapes included wide flanges, double-angles, double-channels, structural tees, thin and thick-walled pipes, and thin and thick-walled square tubes. The responses of the specimens are evaluated and special attention paid to the effects of cross-sectional shape, end conditions, and slenderness ratio using hysteretic envelopes. While investigating the major parameters that influence a member's performance under cyclic loading, some important properties were recognized and quantified. Reduction factors were developed, which can account for the Bauschinger effect and initial curvature of struts. These factors can be used with an AISC code determined load to estimate the deteriorating compressive capacity of a strut during a few consecutive cycles of full inelastic load reversals. Some design recommendations are made for build-up members likely to experience severe load reversals.