Techno Press

Steel and Composite Structures   Volume 24, Number 2, June10 2017, pages 227-237
Optimization of long span portal frames using spatially distributed surrogates
Zhifang Zhang, Jingwen Pan, Jiyang Fu, Hemant Kumar Singh, Yong-Lin Pi, Jiurong Wu and Rui Rao

Abstract     [Full Text]
    This paper presents optimization of a long-span portal steel frame under dynamic wind loads using a surrogate-assisted evolutionary algorithm. Long-span portal steel frames are often used in low-rise industrial and commercial buildings. The structure needs be able to resist the wind loads, and at the same time it should be as light as possible in order to be cost-effective. In this work, numerical model of a portal steel frame is constructed using structural analysis program (SAP2000), with the web-heights at five locations of I-sections of the columns and rafters as the decision variables. In order to evaluate the performance of a given design under dynamic wind loading, the equivalent static wind load (ESWL) is obtained from a database of wind pressures measured in wind tunnel tests. A modified formulation of the problem compared to the one available in the literature is also presented, considering additional design constraints for practicality. Evolutionary algorithms (EA) are often used to solve such non-linear, black-box problems, but when each design evaluation is computationally expensive (e.g., in this case a SAP2000 simulation), the time taken for optimization using EAs becomes untenable. To overcome this challenge, we employ a surrogate-assisted evolutionary algorithm (SAEA) to expedite the convergence towards the optimum design. The presented SAEA uses multiple spatially distributed surrogate models to approximate the simulations more accurately in lieu of commonly used single global surrogate models. Through rigorous numerical experiments, improvements in results and time savings obtained using SAEA over EA are demonstrated.
Key Words
    structural optimization; steel portal frames; equivalent static wind loading; SAP2000; surrogate-assisted evolutionary algorithm
(1) Zhifang Zhang, Jingwen Pan, Jiyang Fu, Jiurong Wu, Rui Rao:
Guangzhou University-Tamkang University Joint Research Center for Engineering Structure Disaster Prevention and Control, Guangzhou University, Guangzhou 510006, P.R. China;
(2) Hemant Kumar Singh:
School of Engineering and Information Technology, University of New South Wales, Canberra, Australia;
(3) Yong-Lin Pi:
Centre for Infrastructure Engineering Safety, University of New South Wales, Sydney, Australia.

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