Cyclic Behavior of Steel Double Angle Connections

摘要

To study the inelastic cyclic behavior of double angle steel connections, six full-scale assemblages of beam-to-column connections were subjected to severe cyclic loadings simulating the effects of strong earthquakes. The connections consisted of two equal leg angles welded to the web of the beam and bolted to the column. Steel used in the specimens was A36. The bolts were 3/4 inch A325 or A307 rib bolts. The major parameters studied were moment-rotation hysteresis behavior and variations in the bolt force. Some bolts were instrumented with strain gages, and the connection was instrumented to measure moment and rotations as well as bolt forces. The specimens were subjected to increasing levels of cyclic rotation, with each level of rotation repeated. The results include moment-rotation cyclic hysteresis loops and cyclic bolt force variations, as well as qualitative observations. The failure modes observed were bolt tension failure, thread stripping off, and cyclic fatigue fracture of angle legs. Results of bolt pull tests and material tension coupon tests are also reported. The main conclusion was that the connections with A325 bolts tightened to 70% of proof load behaved well. Whereas, in some cases, connections with ribbed bolts were brittle and failed in early cycles through bolt thread stripping.