## 2 Methodology
### Numerical Simulation of the Steel Plate Composite Structure  
Steel plate composite structures are affected by various factors, such as raw materials, welding conditions, and testing conditions. In this study, field application verification tests were conducted to verify the performance of the structures. Based on the field test results, finite element calculations were also performed to investigate the relationship between the initial peak value and the constant resistance value of the multi-specification steel plate composite structure. This study provides a solid foundation for the development and application of backward energy-dissipation supports. Imposing a vertical displacement constraint on top of the upper connecting steel plate set the constraint on both sides to slide vertically only. In addition, a fixed constraint was arranged at the bottom of the lower connecting steel plate. The unit is a hexahedral 20-node reduced integration unit, and to consider the post-flexion state, the vertical plate and the connecting plate are set to be in self-contact, the contact does not consider tangential friction, and the contact mode was set  
Figure 6: Schematic diagram of the loading device: **(a)** Picture of the instrument; **(b)** Picture of the loading process  
Figure 7: The deformation process of the steel plate composite structure. to \"hard contact\", and the finite element analysis model is shown in Figure 8. Since the connecting plate is only a force transmission member, not the main body of analysis, and is connected with other materials in engineering applications, the upper connecting steel plate and the lower connecting steel plate were made of elastic material, and the vertical steel plate was made of elastic-plastic material, the calculated parameters of which are shown in Table 1. Vertical steel sheet material parameters are based on ex-factory parameters and the results of [PERSON] et al. 's work on Q235 steel stress-strain curves [25], inverted from the average veneer constant resistance values obtained from the tests. Since the performance of a steel plate composite structure is determined by its vertical steel plate, the required thickness and height of the latter were investigated as part of the present study, the calculation conditions of which are shown in Table 2 below. The finite element model was established via ABAQUS, and the calculation was carried out according to the boundary conditions mentioned above. Selecting the same data as the numerical simulation for statistics, the finite element calculation results are shown in Figure 9. The compression of the steel plate type restrictor reaches more than 75%, has a large stroke, and can fully dissipate the pressure of the surrounding rock. Since the model material of numerical simulation is uniform, the result is relatively large, but the \begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**Steel Plate Composite Structure**} & **Elastic Parameter** & \multicolumn{2}{l}{**Plastic Parameter**} \\  & **Elastic Modulus** & **Poisson’s Ratio** & **Yield Stress** & **Plastic Strain** \\  & \(E\) **(Gpa)** & \(\mathbf{v}\) & \(\mathbf{\sigma p}\) **(MPa)** & \(\mathbf{\epsilon p}\) \\ \hline Upper and lower connecting plates & 200 \(\times\) 10\({}^{3}\) & 0.3 & — & — \\ Vertical plate & 200 & 0.3 & 320 & 0 \\  & 200 & 0.3 & 650 & 0.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Table of calculation parameters. Figure 8: Finite element analysis model. accuracy rate is more than 95%, which can be determined that the calculation method used is correct and reasonable, as shown in Table 3.  
The stress-deformation curves of the steel plate composite structure under five working conditions are shown in Figure 10. Based on the validation test results, the working period of the steel plate composite structure can be divided into four main stages. The first stage is the elastic deformation stage, characterized by a linear increase in pressure with deformation.