Development of the tied butterfly shape for structural fuses

Abstract

Recently, there has been research and interest in structural fuses as a way to concentrate seismic damage in replaceable elements and protect the rest of the structure from inelastic actions. However, there is no consensus on structural fuse shape, particularly for structural fuses consisting of a steel plate subjected to shear deformations, because studies with different objectives arrive at different shapes. For example, studies seeking to optimize the structural fuse shape to maximize fracture resistance often result in something that looks like the butterfly-shaped link, whereas other studies that optimize the form to maximize buckling resistance result in a shape with links that are tied together. In this study, a new structural fuse shape, named the tied butterfly shape, was developed to integrate the advantages of both the buckling-resistant configuration and the butterfly-shaped link. First, the concepts for the tied butterfly shape are presented along with plastic mechanism analysis to derive an equation for shear strength. Then, an experimental program is described including three tied butterfly shape structural fuses and one straight link structural fuse for comparison. Finite element models are then validated against the experimental results and a parametric computational study is presented that evaluates the effect of key design variables on the structural behavior of this tied butterfly shape. The experimental study revealed that the tied butterfly shape structural fuse was capable of maintaining stable hysteretic behavior up to a shear angle of 23% before fracture or buckling and that multiple tied butterfly shapes can be connected together. Based on the plastic mechanism analysis and parametric study, design equations and recommendations for implementation in practice are provided.