# The Resistance of Welded Joints of GAlvanized RHS Trusses with Different Vent Hole Geometries
## 2 Finite Element Modeling  
The general-purpose finite element software Ansys Workbench (Ansys Inc, Canonsburg, Pennsylvania, PA, USA) was used to carry out a numerical analysis to determine the most efficient geometry of vent holes with respect to both the joint resistance and the amount of molten zinc recovered. The model complexity in cases of welded joints between RHS can vary, and ranges from shell elements at the mid-surface of the faces without any element simulating the weld bead through to solid 3D elements including the welds [29]. In the case of T and X joints, the simplest option (shell elements without welds) has been demonstrated to be sufficiently accurate to obtain the static strength of joints [30]. However, the most common truss joints (K- and N-type) have two braces welded to a chord, and the consideration of the actual gap between welds--not only between the chord faces--is essential to evaluating their strength, especially when these gaps are appreciable. Multiple simplified shell models were tested [29; 30; 31; 32; 33; 34], and the best approximations without increasing complexity were those based on the proposals made by [PERSON] et al. [32] or by [PERSON] and [PERSON] [33]. The inclusion of the welds in numerical models of steel tubular trusses is also important when considering cyclic loads, as it is necessary in cases where there is some damage to the constitutive model of the welded joints [34]. To obtain an accurate and efficient simulation, the effect of welds in reducing the gap, and thereby stiffening the joint, was ultimately modeled in this research work by means of a ring of shell elements around the braces based on the geometry proposed by the latter authors [33], as presented in Figure 1.  
Figure 1: Weld geometry modeling with shell elements (A–B and C–D). The thickness adopted for the shell elements of the welds was equal to the chord thickness. In practical terms, this is similar to the weld throat proposed by the CIDECT for joints between hollow sections [9]. K-joints and N-joints were considered in this work. For either of these, four different models, selected depending on vent hole presence or geometry, were analyzed. All of the studied joints included a parametrically variable gap that was dependent on the rest of the joint dimensions. The first model did not include any vent holes and was used to validate the numerical model on the basis of a comparison with test results. Once the initial model was validated, it was extended to consider three different vent hole geometries and positions in order to determine the best proposal. Figure 2 shows these three configurations. Figure 2 shows a circular hole of diameter \(D\), located 18 mm away from the chord face, which was the same location considered in our previous work [26; 27]. This configuration reduces the stress concentration around the hole and does not shorten the weld length; on the other hand, some liquid is retained inside the brace. Figure 2 shows a semicircular hole with a diameter of \(\sqrt[]{2}xD\) to maintain the same filling area as the previous circular one. Figure 2 shows a V-notched vent hole that presents a lower cut-off of the weld when compared with the semicircular hole, while maintaining the same filling area as the other two proposals. The two configurations shown in Figure 2,c allow the total recovery of liquid after the galvanization process, but they need to cut off the weld between the braces and the chord. As stated previously, the three geometries maintain the same filling area. This area always refers to the area of the circular hole, whereby the diameter \(D\) was assumed to be 25% of the X-section diagonal of the corresponding brace, in accordance with the recommendations in [25]. Therefore, in the case of a semicircular hole, the diameter is \(\sqrt[]{2}xD\). Nevertheless, for the V-notched configuration, some new design variables were taken into account (Figure 2). These are the dimensions \(2B\)--that is, the maximum opening--and \(H\), which is the height of the notch.