Seismic design and numerical assessment of shape memory alloy-restrained rocking precast concrete bridge columns

This paper introduces a class of shape memory alloy (SMA)-restrained rocking (SRR) bridge columns and numerically evaluates their response under lateral loading. SRR columns are low-damage precast concrete columns that are connected to their adjacent substructure components through two series of unbonded links, namely, SMA links and energy dissipation (ED) links. The SMA links, which are prestressed and made of superelastic Nitinol, provide the rocking joints with self-centering and dissipate a moderate amount of energy. The ED links, which are made of mild steel and are replaceable, supplement the hysteretic energy dissipation provided by the SMA links. The rocking joints are protected against concrete damage via steel jacketing and end steel plates. Following the introduction of three SRR column design variations, a displacement-based procedure is proposed for their effective seismic design. Nonlinear 3D finite element models are then developed to investigate the performance of the proposed columns under monotonic and cyclic lateral loading. Finally, a parametric study is conducted to examine the effective ranges of two major design parameters of SRR columns. The findings illustrate that the proposed SRR columns are capable of meeting their targeted performance objectives, i.e., avoiding damage under the displacement demands induced by a 2475-year seismic event, as well as providing significant self-centering and hysteretic damping.