Studying the Ductility Factor for Middle Gusset Connections in Chevron Braced Frame Configurations

Chevron bracing is a common configuration for concentrically braced frames. Typically gusset plates are used to connect the braces to the frame in such braced frames. One of the common issues in brace connections is the uneven stress distribution across the welded gusset edge. The development of a peak stress induced at some point across the welded connection might cause the weld to fail at the point where the stress is concentrated causing an unzipping of the weld and a progressive failure of the welded connection. A weld ductility factor has been used to account for the uneven connection stress distribution. However, the limited experimental work on which the ductility factor is based was performed considering only corner gussets. This study evaluates the ductility factor value for chevron (middle) gusset plate connections. In order to do so, a group of twenty assemblies, each consisting of a beam, rectangular gusset(s) with chavron V- and X-type bracing configuration, and the beam to gusset(s) weld connections are designed, and then modeled in a finite element software to check the stress distribution along the weld line. Based on the obtained results, the common weld ductility factor value should be increased to a larger amount for the case of chevron gusset plate.