Gene expression model to estimate the overstrength ratio of short links

Abstract

Short links are used as fuse members in Eccentric Braced Frames (EBFs), hybrid coupled-wall systems, and self-anchored suspension steel bridges. Compared to the intermediate and long links, short links have superior performance such as high strength and plastic deformation capacity. However, several researchers observed a considerably high overstrength ratio for short links. This study found that the AISC Seismic Provisions underestimate the plastic shear strength of short links, the experimental results of 103 specimens showed that only 8% of the specimens comply with the recommended AISC Seismic Provisions overstrength value of 1.25. The average of all data is 1.67 with COV 17.6% and RMSE 0.732. Therefore, a genetic expression-based model (GEP) was proposed to estimate the plastic shear strength of short links. A 96% of the overstrength ratio calculated by GEP of the 103 specimens comply with the recommended AISC overstrength value of 1.25. The average of the GEP overstrength values is 1.00 with COV 13.6% and RMSE 0.136. The GEP model considers the contribution of six variables such as the flange slenderness ratio (bf/tf), the web slenderness ratio (d/tw), the flange to web area ratio (Af /Aw), the flange force (Af fyflange), the web force (Awfyweb), and the link length ratio e/(M/V). Unlike the AISC overstrength ratio estimates, the GEP predictions are not sensitive to the variables. This is evidence that the GEP model is an inclusive and efficient equation to estimate the overstrength ratio of short links.