# A Component-Based Model for Novel Modular Connections with Inbuild Component
## 4 Validation  
### Intramodule Connections  
The simplified finite element model of the intramodular connection was shown in Figure 41a. The floor beam (or ceiling beam) was modeled by the B3 IOS element in Abaqus, while the column was modeled by the B31 element. A rotational spring was placed at the intersection point between beam and column, which were modeled as connectors with \"join and revolution\" in Abaqus. The moment-rotation relationship of the spring was calculated through the method described in Section 3. To verify the accuracy of the simplified model, more refined models were built using a shell element as shown in Figure 41b. The column bottom face was pinned to the ground, and the material properties were consistent with the model in Section 2. The letter B followed by a number indicates the height of the beam, the letter P indicates whether the influence of inbuild component was considered, the letter G followed by a number represents the allowable error and values were considered, and the letter M means the simplified model. The thickness of inbuild component (\(t_{p}\)) was 10 mm. The other dimension details were the same as the refined finite element model in Section 2. Figure 41: Finite element model of intramodule connection for validation. (**a**) Simplified finite element model; (**b**) Refined finite element model. Figure 40: Spring-based model for intramodule connections. The comparison results between simplified and refined finite element model were shown in Figure 42. Figure 42a shows the moment-rotation curves without setting the inbuild component. When the connection was subjected to the positive bending moment, the \"I\" region was in compression and the \"II\" region was in tension. \"II\" had low mechanical properties as compare to \"I\" due to its proximity to the column open end. Therefore, the failure mode of the connection was the tension failure at the \"I\", and the beam had not reached its ultimate bearing capacity. The same conclusion can be deduced when the connections were subjected to negative bending moment but with the compression failure at \"II\". The curves of the simplified and refined finite element mode were almost coincided in elastic stage. In the nonlinear stage, the curve of the simplified model was slightly higher than that of the refined finite element method. Figure 42b shows the results of connections enhanced by the inbuild component under the positive bending moment. The inbuild component enhanced the stiffness and strength of the \"I\" part but had little effect to the \"II\" region, so the failure mode of the connection was still the tension failure of the \"II\" region. The results of simplified model were in good agreement with those of the refined finite element in linear stages. In the plastic stage, the curves of the simplified model were close to horizontal, while the curve of the refined finite element model showed a trend of slow decline. Figure 42c showed the comparison results under the negative bending moment with the inbuild component. The simplified model agreed well with the refined finite element model in the elastic stage. There was no obvious elastic-plastic stage in the mechanical model, and the ultimate bending moment in the plastic stage is slightly lower than that predicted by the refined finite element method. Under the negative bending moment, the \"I\" region was in the tension state, and the \"II\" region was in the compression state. The existence of the inbuild component greatly enhances the compressive stiffness and strength of the \"II\" region, and thus it improves the initial stiffness and ultimate bearing capacity of the connection (Figure 37). Therefore, the failure mode of the joint was that the plastic hinge was formed at the joint beam. When there was construction error between the inner plug-in and the node column, the moment-rotation curves under the negative bending moment were shown in Figure 42d.