Fast Procedure for Practical Member Sizing Optimization of Steel Moment Frames.

A conceptually intuitive, computationally efficient iterative procedure is formulated to optimize the member sizes of regular steel moment frames under both lateral forces and gravity loads. This procedure aims to maximize the interstory drifts of a steel frame while satisfying code requirements on both individual member strength and story lateral stiffness. Akey premise of the present optimization method is that the process of pushing the interstory drift profile of a steel frame toward the code-specified interstory drift limit (i.e., attaining a fully drifted state) is inherently accompanied by a reduction in the total steel weight of the frame. To attain the desired fully drifted state, an iterative scheme for the story-by-story updating of the column and beam sizes is provided. At each iteration, a steel member is resized according to the worst of its strength demand-to-capacity ratio and the interstory drift demand-to-limit ratio. The iterative process continues until the total steel weight of the frame has been reduced to a satisfactory level, and both member strength and interstory drift have met the code requirements. Member sizing optimization of three example steel moment frames with varied complexities is carried out using the present iterative procedure. Numerical results show that an improved frame design can be generated within a few iterations, and that this design compares favorably with the baseline frame design that results from weight minimization by either an exhaustive enumeration or a genetic algorithm. Therefore, the present iterative procedure is an appealing tool for practical design optimization of steel frames. [ABSTRACT FROM AUTHOR]