Seismic Performance of Optimal Steel Moment Frames with Variation of Design Load Patterns

As a common practice, well-known building codes provide simplified design procedure based on equivalent lateral loading patterns, instead of performing rigorous dynamic step-by-step analyses. The present study concerns the effect of such lateral loading patterns on distribution of stiffness and strength in the structure and the resulted dynamic responses including failure sequence in the moment frames. Utilizing a genetic algorithm, design of the frame is fixed via sizing optimization under the corresponding equivalent static loads. Consequent structural responses for every such design are then derived via non-linear time-history analyses. Several issues are investigated in order to compare and rank the design patterns including minimal structural weight, sequence of plastic hinge formation and period shift due to non-linear seismic behavior. The results declare that the common code-based pattern is not necessarily the best in all the cases. Particularly, the proposed uniform-triangular distribution of base-shear can guide formation of plastic hinges to start from the less-critical stories in progressive collapse of moment frames

Keywords:

Optimal seismic design , Loading pattern , Steel building frame , Genetic algorithm , Non-linear dynamic analysis