# Experimental and Numerical Studies on the Structural Performance of a Double Composite Wall
## 5 Conclusions  
In this paper, experimental and analytical studies were conducted on a double composite wall (DCW) that is suitable for large-scale basement wall construction. The failure patterns, flexural and shear responses, and slip between the PC panel and the CIP concrete of the specimens were measured and analyzed in detail. A non-linear flexural analysis was performed on the flexural specimen, and a finite element analysis was carried out on the shear specimens to quantitatively evaluate the flexural and shear performances of the DCW. In addition, a straightforward calculation method for the practical shear design of DCW was proposed based on the current design codes. On this basis, the following conclusions can be drawn:  
1. The end slip between the PC panel and CIP concrete in the flexural and shear specimens was only 0.02 and 0.03 mm, respectively, and the composite performance of the  
Figure 13: Shear strength estimation methods for DCW.  
PC panel and CIP concrete was found to be excellent. This is because rough surface finishing was applied to the PC panel, and the shear keys of the upper and lower panels were interlocked with each other.
2. In the composite DCW, although the bolts used for assembling the PC panels contributed considerably to the shear resistance mechanism of the member after inclined shear cracking, they failed to exhibit the yield strain until the maximum load was reached. This is because the bolt was not fully embedded in the PC panel concrete, but instead was composite with the PC panel by grout injected into the bolt hole during the assembly process; thus, the bolt and the PC panel failed to achieve fully composite behavior.
3. The non-linear flexural analysis model provided very good estimations not only of the flexural strength of the DCW member but also of its initial stiffness and post-cracking stiffness. Therefore, the non-linear flexural analysis model proposed in this study can be adequately applied in the design of DCW and the prediction of its flexural behavior.
4. The finite element analysis results showed that when the bolt and the PC panel were assumed to be fully composite, the finite element model overestimated the shear strength of the specimen. However, when the constitutive laws for the bond-slip relationship suggested in the _fib_ model code 2010 were taken into account, the analysis model evaluated the shear behavior of the specimen well, including the shear contribution of the bolts according to the load. In addition, the proposed practical equation, which considers the shear contributions of all the elements constituting the DCW section, provided reasonable shear strength estimation results on the safe side in a simple manner.
5. The flexural and shear performances of the DCW member were investigated in this study. For the DCW to be practically applied to construction sites, however, additional experimental and analytical research needs to be conducted regarding the flexural behavior at the foundation-DCW connection.  
Original draft manuscript, S.-J.H.; validation, I.H.; investigation, J.-H.K., Y.-H.O; supervision and review writing, K.-S.K. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2020R11A3054759).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.