Seismic reliability-based design optimization of steel structures

The seismic design of steel moment frames is a complex process that incorporates seismic demand with a structural capacity to attain safe buildings aligned with specified constraints. An intuitive approach is a must to initiate the design, but it is inadequate to yield efficient design solutions because of interrelated design parameters. This study presents a computationally efficient algorithm for the seismic reliability-based design optimization of steel moment frames. The new base shear force equation introduced in this study combines the seismic demand statistics with the reliability objective to calculate a fictitious base shear force for linear static analysis. By concentrating on the seismic demand and promising to meet a certain level of reliability, the equation converts the reliability-based design optimization problem to a code-based deterministic design optimization one. Four real-size moment frame groups with different heights are optimized with respect to target reliability levels to demonstrate the competence of the proposed procedure. The optimization procedure starts with the ground motion selection and continues with iterations to yield the least weight structure. The seismic reliability of the optimized frames is evaluated through response history analysis, and the results prove the legitimacy of the proposed reliability-based optimization procedure. Although the proposed algorithm does not pledge to find a global optimum design solution, the efficiency and ease of use of the proposed algorithm make it a powerful tool for improving the design-related decision-making process of real-size structures.