# Numerical Study on the Bending Resistance of Lightweight Built-Up Steel-Concrete Composite Beams
## 3 Parametric Numerical Analysis Results
### Influence of CW Thickness and Spot Weld Density
#### 3.7.2 Partial Shear Connection  
The influence of spot weld density in cases of partial shear connection is shown in Figure 16 with regard to models with steel beam heights of 400 mm, 500 mm, and 600 mm. Different CW thicknesses are analyzed for steel beams of the same height and with the same degree of shear connection. In accordance with the results in Figure 16a, where models with CW thicknesses of 1.0 mm (400_SP10_CW10) and 1.5 mm (400_SP10_CW15) are presented, and which have shear connectors positioned in pairs (SC12C) and steel beam heights of 400 mm, it is concluded that in the analyzed cases, the influence of the CW thickness is 25-30 kNm for the difference in thickness of 0.5 mm. The influence of the spot weld density in the analyzed models is negligible. In Figure 16b, the same thicknesses are analyzed, but the shear connectors are presented in a staggered arrangement (SC12S). Again, the bending capacity difference caused by spot weld density is negligible compared with the impact of CW thickness. In Figure 16c, only the influence of spot weld density is analyzed in models with a steel beam height of 500 mm and a CW thickness of 1.0 mm when the shear connectors are arranged in pairs (500_SP10_CW10_SC12C). The difference in bending capacity is approximately 20 kNm. Figure 16d shows the analyzed influence of a steel beam height of 600 mm, a CW thickness of 1.0 mm (600_SP10_CW10) and 1.5 mm (600_SP10_CW15), and an arrangement of shear connectors in pairs (SC12C). After observing models with the same CW thicknesses, the difference was found to be negligible, but after observing models with the same spot weld densities and different CW thicknesses, the difference is approximately 15%.  
Figure 15: Influence of CW thickness on the deformed shape and von Mises stress fields of the steel beams: (**a**) 600_SP10_CW08_TIE_02; (**b**) 600_SP10_CW15_TIE_02.  
Figure 17 shows the deformed shape and von Mises stress in model 400_SP10_CW10_S C125_02 during the last stage of analysis. The view cut was made in the longitudinal plane, wherein shear connectors were placed in a staggered arrangement. In Figure 17, one side of the shear connectors is shown, and in Figure 17, the other C profile with shear connectors is shown in its final stage. It is evident that the shear connector on one side of the beam failed.  
Figure 16: Influence of CW thickness and spot weld density on partial shear connections: (**a**) steel beam height of 400 mm and shear connectors positioned in pairs; (**b**) steel beam height of 400 mm and shear connectors positioned in a staggered arrangement; (**c**) steel beam height of 500 mm and shear connectors positioned in pairs; (**d**) steel beam height of 600 mm and shear connectors positioned in pairs.  
The influence of steel beam height on models with partial shear connections and different spot weld densities is shown in Figure 18.  
A comparison of models with the same steel beam height is shown in Figure 18a; it is concluded that spot weld density does not have an influence on the bending capacity of the analyzed steel beam with a CW thickness of 0.8 mm. To confirm the aforementioned conclusion, Figure 18b shows results for the steel beam height of 600 mm and CW thickness of 1.0 mm. The impact of the spot weld density is still negligible. On the other hand, in Figure 18c, models with a CW thickness of 1.5 mm are shown, and some small differences in bending capacity, up to approximately 15%, between beams of the same heights, can be observed.