## 3 Analyzing Experimental Phenomena and Results
### Damage Modes and Finite Element Analysis  
Using the classical calculation method combining [PERSON]'s equivalent intercalation theory with [PERSON]'s model, the ECC material containing PVA fibers was equated to a single dielectric material, and the parameters for homogenization of the composite were calculated as shown in Table 6.  
Accordingly, the plastic damage model of ECC material can be determined and its intrinsic structure relationship is determined according to the uniaxial compressive and tensile stress-strain relationship of concrete according to the specification of the \"Technical Specification for the Application of Fiber Concrete JGJ/T221-2010\". ABAQUS finite element analysis software was used to perform the test force analysis on the plate members of this test. Among them, the ECC and steel plate were simulated by the C3D8R three-dimensional solid unit, which can greatly improve the computational efficiency by using the integration method of nodes with three translational degrees of freedom and eight nodes forming a unit. The mesh size of the steel plate is 10 mm, and the mesh size of the ECC plate is 5 mm; the steel reinforcement is simulated by the two-node 3D T3D2 of the truss unit and the mesh size is 50 mm, and it is embedded in the ECC in \"Embedded\" mode, corresponding to the test member SE-50-150-1; and the established finite element model is shown in Figure 10. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Materials** & **Density/(kg\(\cdot\)m\({}^{-3}\))** & **Elastic Modulus/GPa** & **Poisson’s Ratio** \\ \hline PVA-ECC & 2213 & 35 & 0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Performance parameters of ECC composites after homogenization. Figure 8: ECC cracking photo. Figure 9: Load-crack width curve. (**a**) Group 1; (**b**) Group 2. The ultimate load calculated by the finite element model is 28.64 kN, which is consistent with the test results, and the error is controlled within 10%. The reason for the error may be that the model calculation of the composite material and the assumptions and simplifications made by the CDP plastic damage model for ECC do not perfectly match the real material, and, in addition, the embedding and connection of the bolts and reinforcement also deviate from the actual situation to some extent. By defining the parameters of the tensile damage factor in the CDP plastic damage model in ABAQUS software, a tensile damage cloud of the structure was obtained, as shown in Figure 11. The tensile damage in the model is very similar to the crack distribution in the test process and results, with cracks appearing early and concentrated in the pure bending section and relatively late and scattered in the non-pure bending section. After the test unloading, the whole specimen showed an obvious rebound phenomenon, but the ECC layer did not peel off as a result, indicating that the ECC has high ductility and the steel plate did not yield during the whole loading period. Finally, a large area of cracks appeared in the flexure-only section of the lower ECC layer, and the load-bearing capacity was lost, explaining the damage to the member. The CDP model of the combined structure established by the inclusions theory can more accurately simulate the force of the test specimen throughout the test process, the inclusions theory, and CDP damage model, but there are certain errors that include: (1) the Eshelby-Mori-Tanaka single inclusions theory yielded elastic mode tends to be homogeneous, and the actual model of multiple inclusions mixed material properties there is a certain error; (2) the CDP model is a simulation method of isotropic elastic damage superimposed on anisotropic tensile and compressive plastic damage, while the ECC is a non-homogeneous and complex mechanical property, which forms an elastic-plastic material with considerable ductility after the addition of reinforcement; (3) the embedding mode of reinforcement is idealized, and it is not able to effectively simulate the non-negligible  
Figure 11: Tensile damage cloud.