Probabilistic Modeling of Steel Moment Frames with Welded Connections

Improved building practices for earthquake-resistant design and evaluation rely on accurate nonlinear analysis procedures and a rational approach to dealing with uncertainties. To address building performance issues and support probability based evaluation of steel buildings, two steel moment-resisting frames (WSMF) that suffered damage to welded connections in the Northridge Earthquake are evaluated using deterministic and stochastic approaches. Nonlinear dynamic analyses of these two buildings utilize a new degrading hysteretic connection model that incorporates the effects of weld fractures. The role of inherent randomness and modeling uncertainties in ground motion and structural resistance in forecasting or explaining observed building performance is examined for one of the buildings, leading to a probabilistic description of building performance and insights that are useful for condition assessment and performance based design.