Brace Test

This project enhanced our understanding of the process by which steel structures incur fracture when subjected to strong earthquake effects. The fracture in this case is termed "ductile", because it is driven by the development of inelastic (plastic) deformations. The resistance to fracture initiation and propagation also depends on the stress conditions that a particular region of a structure may experience. Additionally, it may depend on the metal forming process, by which flat steel plates are deformed to give a desired profile shape for a steel member. There is a concern that metal forming may lead to regions in a steel profile, such as the corner regions of a tube profile, where the material resistance to rupture may be different than that in regions away from the corners.
This research included both physical experimentation and computational simulation. Physical experimentation on small steel coupons up to fracture allowed an understanding of the crack formation and propagation process which may occur at critical regions of steel structural members having a hollow rectangular (tube) cross-section. Metal forming was found to have a fairly minor effect on fracture resistance. Further experimental tests on a structural brace having a tubular cross-section, together with computational simulation, provided insights into the process by which local buckling in the thin walls of the tube entails large localized deformations which ultimately cause the formation and propagation of cracks until full fracture of the brace.