Effects of connection fractures on global behavior of steel moment frames subjected to earthquakes

Brittle fractures have been observed in beam-to-column connections of welded steel moment frames following several recent earthquakes. To help understand the effects of connection fractures on seismic safety and response, a series of shaking table experiments and numerical simulations were carried out on a one-third scale, two-story, one-bay moment-resisting steel frame. Simplified mechanical connections were utilized in the experiments to create different types and distributions of fracture behavior. These investigations demonstrate that connection fracture may not always have deleterious consequences, especially when few fractures occur. On the other hand, the experimental and numerical investigations clearly demonstrate that severe strength loss due to the combination of numerous fractures, undesirable postfracture hysteretic behavior, and large excitation can have adverse consequences including collapse.