## 1 Introduction  
Reinforced concrete (RC) is one of the most commonly used construction materials in modern society. However, RC structures deteriorate due to poor initial design, poor construction, aging, and unpredicted use load, and as a result, most RC structures need to be retrofitted using various reinforcement techniques. One of best-known methods for strengthening RC members is the externally bonded reinforcement (EBR) method. The EBR method uses a fiber reinforced polymer (FRP) composite made of carbon fiber, aramid fiber, or basalt fiber attached with an adhesive to external surfaces (e.g., tension zones) of the RC beams and slabs [1, 2]. The EBR method has several advantages, such as simple installation and easy manufacturing, as well as high strength, light weight, corrosion resistance, chemical resistance, and fatigue resistance. However, it is exposed outside, which makes it easily damaged by fire and ultraviolet rays [3]. To overcome these drawbacks, a near surface mounted (NSM) method has been studied, using a FRP strip embedded in a pre-performed groove on the tension zone surface of the beam and slabs. The NSM method has solved the mentioned problems of the EBR method, but suffers because the FRP strip can be separated from the groove early, before the FRP strip is fully tensioned [4]. Several studies from various universities and research institutes have focused on a pre-stressing strengthening (PS) method using a pre-tensioned FRP composite as the strengthening material [5, 6, 7]. One side of the pre-tensioned FRP composite is anchored while the other side of it is pulled using a hydraulic jack installed on the surface of the RC structures. The PS method improves the stiffness and durability of the RC structures, due to its excellent crack control performance [8]. However, installing the anchorage and hydraulic systems for the PS method increases construction cost and time. Furthermore, the tensioned FRP strip cannot be re-tensioned after it relaxes due to concrete creeping and shrinkage. Recently, a study on a strengthening method using a shape memory alloy (SMA) was conducted as an alternative to the pre-tensioned FRP composite of the PS method [9]. SMA is an alloy with the ability to return to its original shape after plastic deformation when heated [10]. When the deformed SMA is embedded in the concrete and heated, the deformation recovery is restricted by the adhesive force between the concrete and the SMA, which creates a recovery stress in the SMA that will act as a compressive force on the concrete. One well-known SMA is the Ni-Ti-based Nitinol, which is mainly used in aerospace and ergonomics. Nitinol is not suitable for the construction field because of its high raw material prices, and lower temperature history [11; 12]. After the discovery of Fe-SMA in 1982 by [PERSON] et al. [13], researchers and engineers in the civil engineering field have used Fe-SMA, which has a lower raw material price than Nitinol [14; 15]. [PERSON] et al. [16] conducted an experimental study to evaluate the mechanical properties and recovery properties of Fe-17 Mn-5 Si-10 Cr-4 Ni(V,C) alloys. He reported that the Fe-SMA exhibited a recovery stress of 300-350 MPa at a heating temperature of 160 \({}^{\circ}\)C. Additionally, it was reported that about 400 \({}^{\circ}\)C is the maximum heating temperature at which the recovery stress of 450 MPa occurs in the Fe-SMA. [PERSON] et al. [17] experimentally evaluated the flexural behavior of RC beams strengthened with Fe-SMA by the EBR method. They reported that the crack load and ductility of the RC beams strengthened with Fe-SMA were significantly increased, compared to those reinforced with CFRP. [PERSON] et al. [18] conducted an experimental study to evaluate the flexural performance of RC beams strengthened with the Fe-SMA using the NSM method. They reported that the crack load and initial stiffness of the RC beams with activated Fe-SMA strips were significantly improved compared to those with deactivated Fe-SMA strips, due to the prestressing effect.