# Structural Behaviour of Concrete Deep Beams Reinforced with Aluminium Alloy Bars
## 1 Introduction  
Conventional steel bars are commonly employed in concrete structures because of their great strength and ductility. Steel bars are nevertheless susceptible to corrosion that can instigate the deterioration of reinforced concrete (RC) beams in the long term [1, 2, 3, 4]. Substitute materials, including non-metallic bars (i.e., fibre-reinforced polymer (FRP) bars), have gained significant attention in recent years since they can stop the reduction of RC beam strength [5, 6, 7, 8]. Although FRP bars have excellent mechanical and physical properties (e.g., corrosion resistance and high strength-to-low weight ratio) [9, 10, 11, 12], unlike metallic bars, FRP bars do not exhibit ductile behaviour with linear-elastic behaviour up to failure [4, 11]. This can lead to brittle failure in RC beams, raising concerns about energy absorption [13]. AA (aluminium alloy) bars are particularly superior to steel bars in terms of corrosion resistance and superior to FRP bars in terms of initial cost and ductility [4, 14, 15, 16, 15]. These characteristics can provide an alternative to using FRP and steel bars in RC beams [4, 14, 15, 13, 15]. Another alternative to steel bars is stainless steel; however, the cost of stainless steel is significantly higher than carbon steel [4, 16, 17]. The main advantage of the AA bar is corrosion resistance, which is provided by a thin, invisible oxide that appears once it has been exposed to the atmosphere [4]. Coating systems have also been used to improve the corrosion resistance of AA materials [18]. Recent research has examined the mechanical properties of aluminium alloys (AA), such as tensile strength and elastic modulus [4, 19, 20, 21, 22]. For example, the tensile strengths, strains corresponding to tensile strengths, and the elastic moduli of AA bars reported by [PERSON] and [PERSON] [4] varied from 344.1 to 378.9 MPa, 2.05 to 2.84%, and 67.7 to 68.3 GPa, respectively. [PERSON] et al. [19] also reported that the tensile strength, elastic modulus, and elongation of AA material varied from 555.69 to 681.86 MPa, 70.69 to 82.26 GPa, and 3.49% to 10.06%, respectively. These investigations have indicated that AA materials reveal a stress-strain curve which is distinct from both FRP and steel materials. The stress-strain curve is characterised by a low elastic modulus and yield plateau, which can directly contribute to energy absorption and ductility in RC beams. All these counted advantages instigated the use of AA materials in structural engineering applications such as the strengthening of existing RC beams, bridge construction, large span roofing, and wall systems [23; 24; 25; 26; 27; 28; 29; 30; 31]. However, the usage area has been limited to strengthening when the bar form is considered [23; 27; 28; 29; 30; 31]. Regardless of its advantages, the behaviour of RC beams reinforced with AA bars has remained underexplored. For instance, only one experimental study exploring the behaviour of RC deep (shear span-to-effective depth (a/d) ratio less than 2.5 [32]) beams reinforced with AA bars was conducted by [PERSON] and [PERSON] [4] based on the author's knowledge. The experimental programme carried out by [PERSON] and [PERSON] [4] included both AA\(-\) and steel-reinforced concrete beams. The investigated main parameters were tension reinforcement ratio and concrete compression strength. It was reported that even if the specimens' concrete strengths vary, the increase in the reinforcement ratio is primarily responsible for the significant increases in the specimens' strength and stiffness. Further investigations are therefore needed. A nonlinear finite element (FE) model based on the Disturbed Stress Field Model (DSFM) [33], which is an upgraded form of the Modified Compression Field Theory (MCFT) [34], has not yet been developed to examine the behaviour of AA RC beams. This would be useful since conducting experimental studies is difficult due to their high cost. However, carrying out numerical studies with verified experimental tests can reduce the cost and time.