Seismic Performance Assessment of Built-Up High-Strength Steel Tubular Columns through Multiaxis Cyclic and Hybrid Simulation

This study investigates the seismic performance of built-up steel tubular (BST) columns composed of four mild-steel plates welded to four ultrahigh-strength steel (UHSS) tubes of Grade 1200, presenting a novel concept in column construction. The focus of this research is to evaluate the behavior of these columns under six degrees-of-freedom (6DOF) boundary conditions, replicating realistic loads induced by seismic events. A comprehensive experimental program was carried out at Swinburne University of Technology, including quasi-static (QS) cyclic and hybrid simulation (HS) tests. These experiments aimed to monitor the progression of physical damage and assess the hysteresis response of the columns, providing valuable insights into their stiffness, strength, and energy absorption capabilities. The results demonstrate the columns' reasonable seismic performance, indicating their potential use in ordinary moment-resisting frames within regions experiencing low–moderate seismic activity.