Shape optimization of butterfly-shaped shear links using Grey Wolf algorithm

Abstract

The shear loading applied to structures is resisted by implementation of hysteric dampers as structural seismic force resisting system. Recently, steel plates with engineered cut-outs are introduced to have controlled yielding. These structural elements behave as shear links are able to post pone brittle limit states, leading to resistance against early fracture. Among which, a promising type of link is butterfly-shaped link, for which the demand moment diagram aligns with capacity moment diagram to efficiently implement the steel. Previous studies show that these elements are used as appropriate choice for structural seismic fuse system since they are able to experience large drifts with sufficient ductility and full hysteric behavior. Therefore, the appropriate geometrical properties for these links are in need of further investigations. In this study, the finite element methodology is initially validated with experimental test. Then optimization criteria is introduced for set of 300 models to investigate the desired geometrical properties for having most energy dissipation with less fracture potential. This paper represents optimization process with which the geometrical properties of butterfly shaped link is improved to have sufficient energy dissipation performance and less potential for fracture. The pushover curves and equivalent plastic strains are obtained from ABAQUS through an iterative process. The Grey Wolf Optimizer method is adopted for optimization methodology due to having strong capability in non-linear system. It can be found that by implementation of optimization methodology the links are designed to have a mode switch from flexural yielding limit state to shear yielding and are able to dissipate energy over a less equivalent plastic strain value.