LESSONS LEARNED FROM THE NORTHRIDGE EARTHQUAKE

The performance of welded connections in special moment resisting fram es (SMRF) during the Northridge, California earthquake in January 1994 was influenced by many variables. The actual ground motions experienc ed by the buildings, the design details employed in the connections, m aterial properties, fabrication workmanship and inspection practices. The evidences of workmanship-related problems were primarily the resul t of lack of conformance to the requirements specified in the AWS Stru ctural Welding Code D1.1, Lack of emphasis on in-process visual inspec tion may have permitted questionable fabrication practices to go undet ected. A fundamental expectation regarding the performance of the SMRF is that of 'ductility'. In concept, the seismic energies are to be ab sorbed by the formation of plastic hinges within the structure. The pr e-Northridge connection detail is examined in light of quality, fractu re and multi-directional stresses, and its relative performance regard ing expectations of ductile behavior. Post-Northridge research specime ns are examined with respect to the same factors, along with their rel ative level of ductile behavior. Details that enhance ductile behavior and the reasons that this behavior can be expected are presented. (C) 1997 Elsevier Science Ltd.