Design optimization of industrial structures is of great importance for engineers in order to provide a cost-effective structural design. Meanwhile, pipe rack is a skeletal industrial structure subjected to various types of loading such as gravity, seismic, piping, and thermal forces. While there are many studies on design optimization of the most common structures, only a limited number of studies exist on optimal design of industrial structures. In this article, a design optimization problem is proposed for weight minimization of steel pipe rack structures, and then the problem is solved through three meta-heuristic algorithms consisting of a modified particle swarm optimization (PSO), grey wolf optimizer (GWO), and the recently developed improved grey wolf optimizer (IGWO). The optimization problem is in discrete form in order to consider practically available cross-sections for the structural members. Stress ratio, drift, and dimensional constraints are imposed during the optimization. In order to demonstrate the capability and effectiveness of the present design optimization problem, a pipe rack structure is optimized by the proposed algorithms, and the optimized designs are compared to an ordinary design in terms of the structural weight and the status of constraints.
