# A Component-Based Model for Novel Modular Connections with Inbuild Component
## 2 Parameter Analysis  
### Establishment and Validation of FEM  
To ensure the logical integrity of the study, the finite element modeling procedure and validation were reviewed briefly. Three full-scale connections experiments were carried out to investigate the basic mechanical behavior. The dimension details and relevant number of specimens were shown in Figure 3 and summarized in Table 1. The reasonable modeling process is the premise to ensure the accuracy of the numerical model. According to [PERSON] [27; 28], a refined nonlinear solid FE model, accounting for the influence of friction, preload of bolts, relative slippage of components, could well reproduce the test result. The typical finite element model was shown in Figure 4a; the loading and support condition were exactly the same as the experiment (Figure 4b). All degrees of freedom on the top and bottom were constrained to achieve a fixed state. A z-direction constraint plane was set at the twin beams to simulate the out-of-plane restraint device in experiment. The bolts and nuts are simplified into cylinders of the same volume, and the pre-tightening force is applied using the \"bolt load\" method in the Abaqus. All contacts between components are modeled using the \"surface-to-surface\" algorithm. Normal contact is simulated by \"hard contact\" to ensure complete pressure transfer and allow separation after contact. Tangential  
Figure 2: The novel modular connection with inbuild component. contact is simulated by \"penalty\" with a friction coefficient of 0.3. All welded parts are modeled as solid units and \"tie\" to surrounding components. To ensure that the model can accurately simulate the local buckling behavior of the web and the flange of the beam, at least two layers of mesh are set in the direction of the thickness of all the member plates. The model was meshed using the C3D8R element with the size of 10 mm at the connection domain and 20 mm in other areas to speed up the calculation while ensuring accuracy. The model contained 94,594 elements and 143,067 nodes. The geometrical nonlinearities were considered through switching \"nlgeom\" on in Abaqus. Material nonlinearities were considered by plastic function in \"material manger\" in Abaqus. For more detailed material parameters, one can refer to the author's previous articles [23]. In the experiment, the load was applied to test specimens through a particular steel bracket. It ensured that the upward displacement of floor and ceiling were equal. In the numerical model, the upward displacement was applied at the bottom flange of the floor beam to achieve the same effect as the experiment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen No.** & **Floor Beam** & **Ceiling Beam** & **Column** & **Stiffener** \\ \hline T1 & [ 250 \(\times\) 140 \(\times\) 10 & [ 200 \(\times\) 140 \(\times\) 10 & \(\square\)150 \(\times\) 150 \(\times\) 8 & None \\ T2 & [ 250 \(\times\) 140 \(\times\) 10 & [ 250 \(\times\) 140 \(\times\) 10 & \(\square\)150 \(\times\) 150 \(\times\) 8 & None \\ T3 & [ 250 \(\times\) 140 \(\times\) 10 & [ 200 \(\times\) 140 \(\times\) 10 & \(\square\)150 \(\times\) 150 \(\times\) 8 & 12 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Structural members of the tested specimens. Figure 4: Loading and support condition of novel modular connections: (**a**) Finite element model; (**b**) Test specimens. Figure 3: Geometric configuration of tested specimens (units: mm). The moment of global modular connection was obtained through the force at loading point multiply by the length of twin beams. The overall rotation was equal to the beam rotation minus column rotation. The comparison of moment-rotation curves between the finite element and the experiment were shown in Figure 5. For T1 connection, the curve of the finite element fits well in the elastic range with that of the experiment. When the moment reaches about 225 kNm, two curves began to separate. The finite element curve is slightly higher than the experimental curve.