# Behaviour Investigation of SMA-Equipped Bar Hysteretic Dampers Using Machine Learning Techniques
## 1 Introduction
During in-plane bending, the yielding process of teeth in these dampers could cause energy dissipation. The E- and C-shaped tools, which dissipate energy due to the plastic deformation of steel materials, were employed as a damper in several other investigations [43]. [PERSON] et al. [44] and [PERSON] and [PERSON] [45] employed steel J-shaped sheets as dampers, which allow the energy to be dissipated by yielding of steel plate under the roll bending. In several research works, U-shaped components were also employed as steel hysteretic dampers [46; 47; 48; 49; 50; 51; 52; 53]. Recently, steel bars are also used as a novel type of hysteretic dampers, in which the two ends of steel bars are connected to two steel plates in order to dispel energy through the bending deformations mechanism. In addition to [PERSON] et al. [54; 55], [PERSON] and [PERSON] [56] evaluated the steel bar dampers with repair capability of bar substitution. The obtained results indicate that steel bar dampers have a high ability to dissipate energy and withstand significant deformations. In an experimental study, [PERSON] et al. [57] considered the steel bar hysteretic dampers (SBHD) as added dampers to elastomeric isolators and proposed a simple method to design them. [PERSON] et al. [58] conducted a comprehensive numerical study on the role of geometrical parameters in SBHD dampers. SBHD with steel bars of different lengths, numbers, and cross sections were analysed in their study, and the seismic behaviour was investigated by utilising hysteresis curves. Moreover, using the multiple nonlinear regression (MNLR) methods, some models were proposed to estimate the behaviour of SBHDs in pre- and post-yielding point sections. Steel bar hysteretic dampers (SBHDs), as added dampers to isolation systems, could withstand strong earthquakes, but the residual displacements result in higher repair costs, lower safety levels, and a significant decline in the ability of SBHD-equipped structures to withstand aftershocks. To overcome this problem, externally bonded composites can strengthen structural components [59; 60; 61; 62; 63; 64]. For the near-fault areas with greater seismic risks, a substation of steel bars with shape memory alloys (SMAs) with recurring properties may be a better option. Scientists found that SMA materials could withstand significant nonlinearities and return to their original shape after unloading. As a result of their excellent corrosion resistance, fatigue resistance, and damping capacity [65], these materials reduce maintenance costs. The use of SMAs for structural purposes has been assessed through some studies throughout the past several decades, including damping devices [66], bridge supports [67; 68; 69], vibrational damage detection systems [70], reinforcement systems [65; 71; 72; 73; 74], and systems of seismic isolation [75]. On the opposite of SMA advantages in improving structural behaviour, earlier studies have demonstrated that SMAs usage poses certain drawbacks as a steel bar in SBHDs. In particular, large-diameter SMAs rebar is difficult to manufacture due to their great hardness [76]. Moreover, due to the fragility of the connecting point in SMA bars, they cannot be welded to steel sections [77]. Therefore, one of the most challenging aspects of using SMAs is the high preparation costs. Despite a decline in price over the past decade, the price for these alloys remains expensive when compared with other contemporary materials. As a result, SMAs are usually used in an optimum manner only in places where more deformation is experienced. Despite several studies conducted on various hysteretic dampers with various geometric shapes, there are still some questions regarding their behaviour, and in particular their behaviour with steel bars. Moreover, the residual displacements in steel bar hysteretic dampers (SBHDs) increase the maintenance and repair costs after earthquakes occurrence.