# The Resistance of Welded Joints of GAlvanized RHS Trusses with Different Vent Hole Geometries
## 1 Introduction
This type of vent hole does not decrease the perimeter welds of the braces, which allows good structural response, but makes it impossible to recover any of the fluid zinc. With the aim of improving this drawback and looking for the best shape of the holes, a new step forward was carried out in [28]. However, considering the conclusions of the many pieces of research on hollow sections that can be found in the bibliography, that initial model required further improvement before being able to provide enough consistency in any conclusions that could have arisen from it. The improvements that are proposed in the present new research work are as follows:  
* The numerical model needed to be validated against experimental results. For this purpose, the main source of experimental values for the development of design equations for welded joints of RHS trusses (i.e., the Delft University test reports) was used. Six tests on K gap joints between RHS were selected, because their observed failure was related to the so-called \"brace failure\" of K welded joints between RHS, which involves both the effective width failure and the local buckling failure on the brace elements. This is because they are clearly the failure modes that are expected to be more influenced by the presence of holes in the brace. * As is clearly stated in the bibliography, in most cases, weld geometry must be modeled in situations where the gaps between the braces are important. However, this was not really modeled in the previous work mentioned, which only considered an estimation of the thermal effects of the weld process. This lack of geometrical weld modeling is solved in this new paper, and the thermal effects mentioned were neglected, since neither the bibliography nor the previous work carried out by the authors [24] showed any appreciable influence of this factor. * The general design of the experiment presented in the previous work was not specifically focused on failure modes that could be more greatly affected by the vent holes. Nevertheless, in the present paper, a parametric study has been designed by selecting joints that, according to the design equations, could represent \"brace failure\" or, in some cases, the \"chord face failure\", which is very close to a \"brace failure\". * The brace lengths in the models of the previous work led to brace buckling in some cases, but not local buckling at the connection location. The brace lengths were reduced in the present work to ensure that the results really showed joint failures. * Elliptical holes were not considered in this work, because they are impractical. * Finally, in this new paper, not only K-joints, but also N-joints were considered. Now, in this new paper, a detailed analysis has been carried out to categorize some different geometries and to determine the best of them in terms of joint efficiency for the K- and N-welded joints, which are present in Warren and Pratt trusses, respectively, which are the two most widely used lattice girders. For this purpose, a finite element model was validated using the results of experimental testing on welded joints between RHS, and then it was extended to take into account the proposed vent hole geometries. The K-joints and N-joints are considered under static loading only. Fatigue loads are not within the scope of this paper. It is worth mentioning that, according to the design codes for trusses in many building structures and some industrial applications, they may be designed considering just static loading. These type of structures with galvanizing vent holes are the focus of this research and some practical recommendations can be extracted from this work.