Finite element analysis of cyclic behavior of steel shear links of different geometry

Abstract

In seismic resilient structural systems like coupled shear wall systems andeccentrically braced frames, a small beam like segment known as the shear link is used as a replaceable structural fuse which dissipates seismic energy primarily by shear deformation. However, the feasibility of interchangeability between the different types of links is yet to be established. Different aspects of links,e.g., stocky short links without stiffeners which are not available in the existing codes need further research. The present study focuses on the numerical investigation of cyclic behavior of shear link to address some of these issues. Several three-dimensional finite element modelsof shear links have been developed considering both geometric and material nonlinearity. The developed models were validated against experimental studies on shear links conducted in the past.With the validated models, studies have been carried on shear links with I-shaped sections and box-type sections. Applicability of existing equations for capacities of shear links having solid webs has been investigated. For shear strength reduction of short links with compact webs, perforated links (links having circular openings in web) have been investigated. Two different patterns of perforations for perforated links were studied and it was found that links with diagonal pattern of perforation can perform better than those with rectangular pattern.The effect of perforation density in link web has been investigated and it was found that dense perforations in link webs result in earlier web buckling during cyclic loading.Certain web compactness limit hasalso been suggested to avoid web buckling of links with even extremely dense perforations. Comparative study on energy dissipation and hysteresis efficiency of different types of links was done.Equal amount of energy was found to be dissipated by two links of the same shear capacity when the shear capacities are based on the suggested equations. However, the hysteresis efficiencies of I-shaped links are found to be higher than those of box-shaped links at rotations less than 0.09 radian. Refined equations for predicting plastic shear capacities of perforated links have been proposed and are validated against finite element analysis results. These equations for perforated shear links can be used in design for achieving cyclic response equivalent to that of a commonly used solid I-link of the same shear capacity.