## 4 Finite Element Analysis Model
### Parametric Analysis  
Using the abovementioned finite element model, we conducted a numerical analysis on this type of composite GFRP-confined concrete square column, and studied the law for the impact of the GFRP layers and the GFRP strip interval on the bearing capacity of the composite column. The specimen design based on the finite element simulation method is shown in Table 8, and the section size and height of the specimen are consistent with that above. Figure 11 shows the impact of the externally wrapped GFRP fiber layers on the load capacity of the composite column. As shown in the figure, when the clear spacing of the GFRP strips is constant, the load capacity of the composite column shows an approximate linear growth with the increase in the externally wrapped GFRP layers. To quantify the role of externally wrapped GFRP layers in improving the load capacity of the composite column, the bearing capacity \(f_{\text{D}}\) of the specimen wrapped with two layers of GFRP strips was used to normalize the load capacity \(f_{\text{u}}\) of the corresponding specimen and obtain the improvement ratio \(f_{\text{u}}/f_{\text{I2}}\) of the load capacity. As shown in Figure 12, with the increase in the wrapping layers, the improvement ratio of the load capacity exhibits  
Figure 11: Impact of the GFRP fiber layers on the load capacity. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimen Number** & **W/mm** & **S/mm** & **L** \\ \hline W50S130L2 & 50 & 130 & 2 \\ W50S130L4 & 50 & 130 & 4 \\ W50S130L6 & 50 & 130 & 6 \\ W50S85L2 & 50 & 85 & 2 \\ W50S85L4 & 50 & 85 & 4 \\ W50S85L6 & 50 & 85 & 6 \\ W50S60L2 & 50 & 60 & 2 \\ W50S60L4 & 50 & 60 & 4 \\ W50S60L6 & 50 & 60 & 6 \\ W50S40L2 & 50 & 40 & 2 \\ W50S40L4 & 50 & 40 & 4 \\ W50S40L6 & 50 & 40 & 6 \\ W600S0L2 & 600 & 0 & 2 \\ W600S0L4 & 600 & 0 & 4 \\ W600S0L6 & 600 & 0 & 6 \\ \hline \hline \end{tabular} Note: _W_—width of the strip—type GFRP fiber cloth, _S_—clear spacing of the strip interval—wrapped GFRP fiber cloth, and _L_—layers of GFRP fiber cloth.  
\end{table} 
Table 8: Design parameters of the finite element model. an approximate linear growth, thereby indicating that the number of externally wrapped GFRP layers is an important factor in controlling the load capacity. Figure 13 shows the influence of the net interval of externally wrapped GFRP strips on the load capacity of composite columns with the same numbers of layers of externally wrapped GFRP. Compared with the load capacity of the fully wrapped specimen, the bearing capacities of the specimens in the W50S40, W50S60, and W50S85 groups decreased by averages of 9.8%, 15.3%, and 16.1%, respectively, as shown in Table 9.  
Figure 12: Improvement ratio of the externally wrapped GFRP layers to the peak carrying capacity. Figure 13: Impact of the clear spacing of the externally wrapped GFRP strips on the load capacity. To analyze the impact of different wrapping methods on the confining effect of GFRP, the ratio of the load capacity of the specimen to the corresponding externally wrapped GFRP area is defined as the peak efficiency of the GFRP (unit: N/mm\({}^{2}\)). Figure 14 reflects that the peak efficiency of GFRP increases with the clear spacing of the external wrapping for a certain number of wrapped layers, thereby indicating that, compared to the entirely wrapped method, the use of GFRP strips for wrapping makes it both convenient for construction and conducive to the full utilization of the material properties of GFRP. To quantitatively evaluate the peak efficiency of GFRP, the peak efficiency of the entirely wrapped GFRP specimen was used to normalize the peak efficiency of the specimen wrapped with the same layers of GFRP strips to obtain the improvement ratio of the peak efficiency of GFRP strips, as shown in Table 10. The results show that, compared with the entirely wrapped GFRP specimens, the peak efficiency of the GFRP strips in the W50S40, W50S60, and W50S85 groups improved by approximately 50%, 70%, and 93%, respectively. Figure 14: Peak efficiency of GFRP.