STABILITY OF DAMAGED STEEL MOMENT FRAMES IN LOS-ANGELES

During the 17 January, 1994 Northridge earthquake a number of welded m oment resisting frames (WMRF) developed cracks in their beam-column co nnections. In this work, the seismic performance of a four-story, a 14 -story and a 27-story moment resisting frame damaged during the Northr idge earthquake is analyzed in order to assess the seismic vulnerabili ty of damaged WMRF's. Analytical models of planar frames with damaged and undamaged connections are developed, and nonlinear analyses are co nducted by subjecting the models to various intensities of the Northri dge-Newhall, Miyagi-ken-Oki, El Centro and Taft records. Analysis resu lts show that the damaged frames behave somewhat like a semi-rigid ste el structure and that, at least in the cases covered by this investiga tion, it does not appear that the damaged structures were susceptible to collapse as a result of the earthquakes used in this study. (C) 199 7 Elsevier Science Ltd.