Seismic performance and most unfavorable and favorable Load distributions of steel storage rack: an optimization approach
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In the current rack seismic design, the load distribution is generally considered to be placed uniformly on the rack, but the reality usually differ. In this paper, the objective is to identify the most unfavorable and favorable load distribution of the braced and unbraced racks under seismic loading through a stochastic optimization - Genetic Algorithm (GA). The GA optimization is performed with an established computational models of racks and the pushover analysis is integrated to evaluate seismic performance of the racks. It is analyzed that the distribution of load has a great influence on the seismic performance of steel racks. During the optimization, including the optimized solutions, there are other loading distributions that will make the racks fail with the seismic requirements. Statistical summary of these load pattern results create a cloud map. The cloud map from the optimization results show that the most unfavorable load distribution is in a ‘凸’ shape of the 3D space of the racks and the safe load distribution holds a ‘凹’ shape for braced racks. Meanwhile, unbracing racks have the characteristics of an unfavorable load distribution of a ‘卩’ shape. The gravity center of the loading has an apparent impact on the braced rack’s seismic performance such as the number of load carried by the columns in the back pulling zone, the total horizontal seismic force, and the distribution of local at the dangerous position. On the other hand, no obvious impact of the gravity.