ABSTRACT
In the years since the 1994 Northridge earthquake when brittle fractures were discovered in welded steel moment connections, much has been learned about the behavior of these connections through both experimental and analytical work. The next logical step is to determine the effects of connection behavior on the behavior of the whole structural system. This paper presents a brief summary of a selection of results from a series of shaking table tests which were performed on a simple steel moment frame test specimen. This specimen was subjected to cosine pulses, which are idealizations of fault-normal, near field ground motions. The observed effects of fracture on the specimen have been subdivided into effects on global and local response quantities and local fracture-induced phenomena. Observed effects on global response quantities include period elongation, increase in maximum and residual interstory drifts, and reduction in base shear. Effects on local response quantities include sharp decreases in moment and more gradual increases in rotation at connections where fracture occurs, as well as sharp reductions in moments in adjacent members. Four local fracture-induced phenomena were observed: sudden change in beam deflected shape, propagation of stress waves away from the fracture, moment redistribution, and excitation of beam higher modes. The extent to which these local phenomena affect the global response is currently under study.
