Experimental and numerical study of self-centring steel column base connection with modular SMA shear dampers

This study presents the development of a novel self-centring steel column base connection (SCCBC) for seismic-resilient structures. The key component in the developed connection is a modular shape memory alloy (SMA)-based damper that exploits combined shear and bending deformation of superelastic SMA bars, which allows an enhanced efficiency of utilising this smart material. Two damper configurations were developed and tested, each employing a different combination of series and parallel SMA bar arrangements. Experimental tests demonstrated an excellent self-centring capability of the proposed dampers, with the ultimate recoverable deformation ranging from 3.2 mm to 7.2 mm. Finite element (FE) simulations of these SMA dampers accurately reproduced the self-centring hysteretic response observed in the experiments. The simulations also revealed pronounced local strain concentrations at the bearing interfaces between the SMA bars and connection plates, in consistence with the experimentally observed indentations, indicating a failure mechanism governed by micro-crack initiation and propagation under cyclic loading. Subsequent FE parametric analyses of SCCBCs further examined the effects of axial load ratio, sequential cyclic loading, and column section dimensions on the connection behaviour. It was found that maintaining an appropriate axial load ratio (e.g., ≤ 0.3) is critical to confining inelastic deformation to the SMA bars and preventing yielding of the steel members. The connection exhibited no significant stiffness or strength degradation under consecutive loading sequences, indicating superior resilience. Additionally, increasing the column section size raises the connection load-bearing capacity, without significantly altering the energy-dissipation capacity.