## 5 Conclusions  
In this study, the prestressing effect by the Fe-SMA bars of the RC beams was investigated both numerically and experimentally. The FE simulation model was developed to investigate the bending responses of the RC beams including nonlinear material properties such as concrete cracking and crushing as well as the plastic deformation of the Fe-SMA bars. By interpreting the numerical results and comparing them with the experimental observations for the RC beams prestressed by the Fe-SMAs in different prestressing scenarios, the following conclusions are drawn:  
* A FE simulation model was developed to investigate the prestressing effect by the Fe-SMA bar on the RC beam bending deformation. The developed FE model took account of concrete cracking and crushing behavior, the prestressing effect by thermal activation of Fe-SMA bars, and the non-linear response of Fe-SMA bars.  
Figure 16: Experimentally observed crack patterns of RC beams after bending fracture with deflection of 40 mm, with various numbers of activated Fe-SMA bars of 5, 4, 3 and 2 [31].  
Figure 15: Concrete cracking and crushing patterns on \(x\)-\(y\) plane developed during RC beam bending, with activated 4, 3 and 2 Fe-SMA bars.  
* The FE model developed in this study was able to capture the bending behavior of the RC beam prestressed with the Fe-SMA bars. The prestressing effect was clearly represented in the bending load-deflection curve predicted by the FE simulations. However, the FE model slightly overestimated the prestressing effect by the Fe-SMA bars. The bending load predicted by the FE simulations was 20-30 kN higher than that obtained in the real experiments. This was thought to be due to the highly idealized perfect bonding assumption between the Fe-SMA bars and the concrete used in the FE simulations.
* The prestress induced by the activation of the Fe-SMA bars was influenced only slightly by the sequence of the activations of multiple Fe-SMA bars. When interpreting the FE simulation results, this was due to the complex bending distortions of the RC beam occurring during the sequential activation of the Fe-SMA bars. However, the bending response of the RC beam was not significantly influenced by the sequence of the activation. Therefore, the activation sequence can be neglected in the FE simulations for calculating the bending deformation responses.
* FE simulations of the RC beams prestressed by different numbers of the Fe-SMA bars qualitatively reproduced the experimentally observed bending deformation behaviors very well. The cracking behaviors of the concrete beams strengthened by prestressed Fe-SMA bars during bending are also well represented by the developed FE models. Although the FE model developed in this study slightly overestimates the prestressing effect, the developed FE model can be used for an optimization study to select the best possible design parameters for prestressing the RC beam with the Fe-SMA bars.  
Conceptualization, Y.-M.Y. and W.L.; methodology, Y.-M.Y.; software, W.L.; validation, Y.-M.Y. and K.-N.H.; investigation, Y.-M.Y.; resources, K.-N.H.; writing--original draft preparation, Y.-M.Y.; writing--review and editing, W.L. and K.-N.H. All authors have read and agreed to the published version of the manuscript.  
This work was supported by Pusan National University Research Grant, 2021.  
Not applicable.  
The data presented in this study are available on request from the corresponding author, upon reasonable request.  
The authors declare no conflict of interest.