Experimental and analytical investigation of the LRFD strength of tapered members

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Virginia Tech

Single story, rigid gable frames are commonly used by the metal building industry for light, industrial buildings. These rigid gable frames are usually constructed of built-up, web tapered, columns and rafters for reasons of economy. The tapering of the webs optimizes the members to develop a fully-stressed design.

The purpose of this study was to investigate the AISC LRFD strength of the rigid knee portion of gable frames. The experimental portion of this study was sponsored by Kawada Industries, Inc., Costa Mesa, California. Eight specimens consisting of a tapered column and a portion of the tapered rafter were tested to failure under three types of loading that approximated the gravity, lateral, and cyclic load cases. The analytical portion of this study investigated the LRFD strength of the eight tapered knee specimens. The calculated LRFD strengths were compared to the experimentally obtained capacities. It was concluded that the LRFD shear strength provisions were overly conservative.

The LRFD shear strength for tapered members was limited to the elastic or inelastic buckling strength of the web plate. Procedures for the application of the LRFD tension field action model to account for the post-buckling strength of tapered webs were presented. The application of tension field action to end panels, panels with large aspect ratios, and hybrid girders was also addressed. It was shown that the application of the LRFD tension field model to tapered members produced less conservative results.