# Numerical Simulation of T Joints Constructed from Hollow Steel Sections
## 4 Analysis of the Results
The maximum local deformation ascertained through the non-linear numerical analysis and the maximum deformation ascertained through experimentation were found to be similar and in the range of 1.03-1.5. Using the non-linear numerical analysis, which errs on the side of caution, larger values of local deformation were achieved in all studied scenarios. The experimentally obtained values showed the best fit with the non-linear numerical analysis results, with a divergence of only 3%. It is significant to notice that local plasticization of the chord element's flange was the cause of the experimentally evaluated connections' bearing capacity exhaustion. An ideal rigid-plastic behavior of the material at the connection site was assumed for the theoretical analysis of the behavior of these connections. The connection showed clear elastic deformation and elastic-plastic behaviors, according to the experimental tests carried out in this work. The implementation of the plasticization line model was necessary for the theoretical concerns. The values that result from using this model were conservative and show the upper bound of the solution. It is feasible to examine several plastic fracture line mechanisms in order to obtain the lowest value, but the values obtained in this way would be non-conservative. Around the node connection shown in Figure 1, behavioral investigations of this connection in the elastic area for a flat state of stress were carried out. The local strain was observed with measurement tape rosettes (angles = 0\({}^{\circ}\), +120\({}^{\circ}\), and \(-120^{\circ}\)). Figure 11 displays the values of the principal strains that were measured. According to EC 3, the figure depicts an incredibly linear condition of stress-strain in an elastic area, which perfectly matches the experimentally determined limit values of forces under limited element deformation. Figure 11 and Table 2 clearly show that the values obtained for the limit value of the force at the connecting point perfectly coincide with the numerical model results. Analyzing the failure mechanism, it was observed that the load capacity of the experimentally analyzed connections was exhausted due to local plasticization of the chord flange, which is entirely consistent with the calculating techniques and procedures described in this study. The assumption behind analytical models analyzing these connections' behavior is that the connecting node exhibits optimal rigid-plastic material behaviors. But, as the study's experimental and numerical results showed, the connection showed notable elastic  
Figure 10: Display of equivalent stresses at the connection in \(\mathrm{daN/mm^{2}}\) for experimentally determined ultimate bearing capacity of connection. deformation and elastic-plastic behaviors. This suggests that the stress condition of the elements is connected to a reserve in the bearing capacity. However, lowering the local deformations is required to raise the connection's bearing capacity. Local deformations and stresses at the connection zone are highly complex and non-linear. Certain restrictions on the connection geometry, such as the ratio of connection element sizes, must be implemented in order to limit local deformations at the connection and avoid a decrease in the rotation/deformation capacity. The main motivation behind this is to meet the requirements of the serviceability limit state. At local deformations of around 1.0% of the element width, the chord element exhibits elastic local deformation or elastic connection behavior. Using the EC 3 rule and nominal yield strain, the connection's ultimate bearing capacity was determined. This value was equivalent to a local chord deformation equal to 0.25% of the chord width. The values of the ultimate bearing capacity that were found experimentally were 2.32 and 2.03 times greater than the value that was determined using the nominal yield strength and the experimentally determined yield strength in accordance with EC 3. This number decreased to 1.23 when seam effects were taken into account.