Inelastic cyclic behavior of bolted flange plate connections

The object of this study is to investigate experimentally several bolted flange plate connections (BFP) to identify the inelastic cyclic behavior and modes of failure. Eight full-scale bolted flange plate connections were tested at the University of Illinois at Urbana-Champaign in 1999. This research was funded by the SAC Joint Venture under the SAC task 7.09. This research is coordinated to develop new design guidelines, which accurately estimate the strength, stiffness, and ductility of BFP connections. The BFP connection specimens were designed to capture two ductile modes of behavior: the hinging of the girder and the hinging of the flange plate. The W24 and W30 girder section were used to study the effect of girder size on the ductility of the BFP connections. In addition, the design details to improve the ductility and to control the failure modes were considered such as the effect of lengthened flange plates, the effect of oversize holes, and the ability of clamp plates to control failure modes.; All of the BFP connections reached 5.0% total rotation and 3.0% plastic rotation without significant strength degradation. The participation of BFP connection components in the inelastic behavior depends upon the relative strength and strain hardening of BFP connection components. The slip behavior results in more energy dissipation for BFP connections. Experimental results have clearly demonstrated that capacity controlled by the net section fracture of the girder is lower than the full plastic bending capacity, which invalidates the current design provisions. The inelastic behavior of BFP connections can be modeled by using several flexural elements and rotational springs. At least two analytical models are needed to represent the behavior: pre-slip model and post-slip model. These analytical models provide a reasonable estimate for the initial stiffness and inelastic behavior of BFP connections.