# Superelastic Shape Memory Alloy Honeycomb Damper
###### Abstract  
The relative displacements between the girders and piers of isolated bridges during intense earthquakes are usually so large that traditional restrainers cannot accommodate the resulting deformation. A novel superelastic shape memory alloy (SMA) honeycomb damper (SHD) is proposed as a means to combine the large strain capacity of SMA and the geometrical nonlinear deformation of honeycomb structures. As a result, the large deformation capacity of the novel damper satisfies the requirements for bridge restrainers. The proposed device consists of a superelastic shape memory alloy (SMA) honeycomb structure, which enables a self-centering capability, along with steel plates that serve to prevent the buckling of the SMA honeycomb. An examination of the SHD was undertaken initially from theoretical perspectives. A multi-cell SHD specimen was subsequently manufactured and evaluated. Following this, numerical simulation analyses of the SHDs using a three-dimensional high-fidelity finite element model were employed to examine the experimental results. In the end, a technique for improving the SHD was suggested. The results indicate that the SHD is able to demonstrate superior self-centering capabilities and stable hysteretic responses when subjected to earthquakes.  
superelastic SMA; honeycomb damper; geometric nonlinearity; long-stroke; thickness of walls +
Footnote †: journal: Applied  
There are also proposals for shape memory alloy (SMA) restrainers that can withstand significant displacement and function as energy dissipation devices [5; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. Re-strainers can demonstrate high fatigue resistance, energy consumption, anti-corrosion, and self-centering abilities with the use of SMA material [26; 27; 28; 29; 30]. Therefore, SMAs are regarded as the optimal material for bridge restrainers. They are capable of reshaping to their initial configuration following a 7% strain deformation, and their characteristic flag-shaped hysteretic behavior allows them to dissipate input energy when loaded [29; 31; 32; 33; 34]. An in-plane deformation behavior analysis and buckling mechanism analysis were conducted by [PERSON] et al. [10] on a Ni-Ti SMA structure with narrow walls. It was observed that the honeycomb structure retains its capacity for self-recovery even after undergoing substantial deformation, provided that the strain of the SMA material remains below 7% (ultimate recoverable strain of SMA material). This affords the honeycomb structure a notable advantage in that it can withstand a maximum macro strain of 41.7%.  
In this paper, a self-centering SMA honeycomb damper (SHD) is proposed, which utilizes the geometrical nonlinearity of honeycomb structures and the superelastic nature of SMA materials to provide large-stroke capacity. Its overall strain is much larger than the local strain [13; 35; 36]. In the introduction, the configuration and operational mechanism of SHD are described. A specimen of SHD is subsequently fabricated and evaluated. A discussion follows the results. Experimental results are then used to validate a three-dimensional finite element model of the specimen. Furthermore, the impact of wall thickness on the properties of the SHD is examined through the implementation of parametric analyses. Additionally, a method to improve the deformation capacity of the SHDs is suggested at last.