Numerical simulation and behavior insights of steel columns with SMA bolts towards earthquake resilience

Abstract

Shape memory alloys (SMAs) are high-performance metallic materials that can experience large strain and still recover their initial shape through either temperature-induced effect (shape memory) or stress-induced effect (superelasticity). The superelasticity of SMAs is very attractive to the earthquake resilient design because of the inherent material feature with excellent self-centering (SC) and energy dissipation capabilities. This paper presents a comprehensive numerical simulation of the steel columns with SMA bolts. A finite element model was validated by tests of two SC steel columns in terms of global hysteresis loops and local strain states. Subsequently, special attention to the effects of prestrain in the SMA bolts, bidirectional loading, and multi-earthquake loading was paid to offer insights into the cyclic responses of the SC steel column. Results showed that the steel columns equipped with SMA bolts could exhibit satisfactory and stable flag-shaped hysteresis loops with excellent SC and energy dissipation capabilities under different loading conditions. In addition, SC column exhibited nearly equivalent seismic performance under multi-earthquake loading. Therefore, the SC steel columns can achieve earthquake resilient design that requires no (or minimal) repair even after strong earthquakes and remains highly functional for immediate aftershocks or future earthquakes.