# Numerical Simulation of T Joints Constructed from Hollow Steel Sections
## 5 Conclusions  
This paper shows the results of the research conducted on \"T\" type connections between cold-formed square hollow-section steel profiles. The experimental and numerical investigations provided the basis for the analysis of the behavior of the studied connections. The local deformation and the load-bearing capacity were determined experimentally and numerically and compared to the analytical solutions obtained according to the EC 3 provisions. The results have confirmed that the exhaustion of bearing capacity of T connections occurs due to the local plastification of the chord flange, which is in accordance with the calculation techniques and procedures described in this study. Furthermore, it was confirmed that the introduced assumption that this type of connection shows elastic-plastic material behaviors is correct, which implies that the stress state shows a certain bearing capacity reserve. This can have an impact on the optimal and rational design of such connections. The observed membrane effects and the post-elastic rigidity of the material after plastic deformations allow the possibility of reducing the local deformation effect and avoiding a reduction in the rotation/deformation capacity by optimizing the connection geometry parameters (for example, by choosing the optimal element size ratio). In this way, an increase in the bearing capacity of the connection can be achieved. Compared to \"Y\", \"K\", \"X\", and \"N\" connections, the experimentally determined value of the bearing capacity of \"T\" connections is lower [20], which can be attributed to the significantly higher sensitivity to local deformations compared to the other types of connections. This also leads to the result that the geometry optimization plays an important role in achieving greater load bearing capacities and points out the necessity of giving more detailed recommendations regarding this aspect. Another significant contribution of this work is the indication of the necessity of taking into account the influence of seams on the real behavior of such connections in analytical calculations. Namely, by taking into account the effect of seams on the bearing capacity, during the analytical calculation procedure, significantly higher and more accurate values can be obtained compared with the experimental and FEM analysis results. It should be pointed out that that fillet welds provide an adequate load-bearing capacity and can withstand uneven distributions of stress and deformation, as well as an adequate rotation capacity at moment connections or at small eccentricities of axial forces. The conclusions point out the necessity of conducting an extensive parametric study in order to update and modify the current European regulations for the design of \"T\" connections for achieving more economical designs. Conceptualization, S.Z. and N.S. ; methodology, D.T. ; software, S.Z. and N.S. ; validation, S.Z., N.S. and D.T. ; formal analysis, M.S.S. ; investigation, M.M. ; resources, M.M. ; data curation, S.Z. ; writing--original draft preparation, S.Z. ; writing--review and editing, M.M. ; visualization, M.S.S. ; supervision, D.T. and M.S.S. All authors have read and agreed to the published version of the manuscript. The results presented in this paper were the result of work at the Center for Civil Engineering and Architecture, University of Nis, and Faculty of Civil Engineering and Architecture of Nis and were supported by the Center's funds. The work reported is part of an investigation within the research project 451-03-65/2024-03/200095, which is supported by the Ministry for Science, Technological Development, and Innovation of the Republic of Serbia. Publicity available datasets were analyzed in this study.