| The numerous brittle failures observed in welded beam-to-column connections during the 1994 Northridge earthquake have raised questions and concerns about the seismic performance of welded special moment-resisting frame (WSR;IF) steel structures. Four WSMFs of different sizes and configurations that suffered connection damage in the Northridge earthquake are evaluated using both deterministic and stochastic approaches. In the deterministic approach, a new degraded hysteretic connection model which incorporates the effects of brittle weld failure is developed based on experimental data. Nonlinear dynamic time domain analyses of these four WSMFs are performed using ground motions representing the Northridge earthquake, and predicted behavior is compared with the actual damage observed. In the stochastic approach, an analysis of variance is performed with respect to the parameters in the degraded hysteretic connection model and the stochastic earthquake ground motion. A detailed uncertainty analysis is conducted for one of the four buildings, and probability distributions of maximum roof displacement angle and maximum inter-story drift angle are constructed. Results using degraded and bilinear connection models are compared. Building fragilities are constructed and are convolved with the seismic hazard to evaluate the reliability of the building; these results compare favorably with independent findings from concurrent research on aseismic design of steel buildings. |
