This paper presents an innovative type of friction sliding bearing system incorporating shape memory alloy (SMA) cables. The study commences with cyclic tests on individual SMA cables to understand their fundamental mechanical properties. The working principle of the proposed SMA-cable-controlled friction sliding bearing (SMA-sliding bearing) is subsequently described, followed by physical tests on two SMA-sliding bearing specimens. The bearing specimens show rectangular hysteresis loops induced by Coulomb friction before the SMA cables are stretched, and afterward the load resistance and energy dissipation capacity of the bearings are increased accompanied by certain self-centering capability due to the engagement of the SMA cables. Such action is expected to effectively restrict excessive displacements of the bearings and to help reduce the residual displacement. Following the experimental study, a theoretical model of the new bearing is developed and numerical simulation is carried out. The theoretical and numerical results agree very well with the experimental results. A case study focusing on a three-span continuous bridge subjected to pulse-like near-fault (NF) ground motions is subsequently conducted, where three types of bearing system, namely, conventional sliding bearing system, SMA-sliding bearing system, and steel-cable-controlled (steel-sliding) bearing system are compared. The system-level analysis results show that the proposed SMA-sliding bearing has its superiority in superstructure displacement control, with a limited increase in the curvature ductility of the pier.

This study presents a novel type of shape memory alloy (SMA) cable-restrained high damping rubber (SMA-HDR) bearing, which is particularly suited to nearfault (NF) regions where the pulsing effect potentially exists in the ground motions. The working mechanism of the bearing is first described, followed by an experimental investigation on a full-scale SMA-HDR bearing specimen. The test results confirm the efficient restraining effect offered by the SMA cables, which contribute to 65% and 24.4% of the lateral load resistance and total energy dissipation, respectively, prior to the initial fracture of the SMA cables. The failure of the cables is initiated near the end grip where moderate stress concentration exists at this region. Following the experimental study, the numerical modeling strategy for the bearing is discussed, and a case study is then presented, demonstrating the application of the SMA-HDR bearings in the Datianba #2 highway bridge, a real project that first adopts the proposed bearings in the world. A simplified design process is introduced for the bridge with novel SMA-HDR bearings to mitigate the potential damage during strong earthquakes especially the NF ones. The system-level analysis on the prototype bridge shows that the novel SMA-HDR bearings equipped with ten 7×7×1.2 SMA cables in each bearing could reduce the average maximum bearing displacement (MBD) by nearly 30% compared with the conventional bridge with HDR bearings. The application of the novel SMA-HDR bearing can significantly alleviate the pounding effect, especially under the NF earthquakes. The presence of the SMA cables tends to increase the maximum force response of the piers, but this effect is minor and under control.

This study proposes a new type of self-centering damper equipped with novel bucklingrestrained superelastic shape memory alloy (SMA) bars. The new solution aims to address some critical issues related to degradation and loss of superelasticity observed in existing tension-only SMA-based self-centering devices, and in addition, to encourage enhanced material utilization efficiency. The cyclic tension-compression behavior of individual SMA bars is experimentally studied first, and subsequently, two proof-of-concept self-centering dampers are manufactured and tested. A simple yet effective numerical model capturing the flag-shaped response of the dampers is then established, and a preliminary system-level analysis is finally conducted to demonstrate the effectiveness of the proposed damper in structural seismic control. The individual SMA bar specimens show asymmetrical flag-shaped hysteretic responses with satisfactory self-centering capability and moderate energy dissipation. Through a specially designed configuration, the proposed damper shows desirable symmetrical and stable hysteretic behavior, and maintains excellent self-centering capability at 6% bar strain. The system-level dynamic analysis indicates that the dampers, as a means of retrofitting, could effectively reduce both the peak and residual inter-story drift ratios of a six-story steel frame. In particular, the mean residual inter-story drift ratio is reduced from over 0.5% to below 0.2% under the maximum considered earthquake, implying elimination of necessary structural realignment even after strong earthquakes.

No abstract

No abstract