Probabilistic Design of Moment‐Resistant Frames Under Seismic Loading

Abstract

This is the second part of a two‐part paper on the development and preliminary testing of a methodology for the optimal probabilistic limit states design of seismic‐resistant steel frames. Part two illustrates the design of a three‐story, single‐bay, moment‐resistant steel frame using a computer‐aided design system called DELIGHT.STRUCT. Linear and non‐linear time history analyses are built into the design procedure itself rather than serving as a check at the end of the design process. The frame's performance is assessed on the basis of its statistical response to gravity loads alone, gravity loads plus a family of moderate earthquakes, and, finally, gravity loads combined with an ensemble of rare severe earthquake ground motions. Design objectives include the frame volume, minimum story drifts and maximum hysteretically dissipated energy. The Phase I–II–III Method of Feasible Directions is used to solve the constrained optimization problem for an optimal design that balances the attributes of minimum volume, minimum story drifts and maximum dissipated energy in a desirable way.