# The Resistance of Welded Joints of GAlvanized RHS Trusses with Different Vent Hole Geometries
## 4 Parametric Study of K- and N-joints Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Joint** & **Chord** & **Braces** & **Circular** & **Semi-Circular** & **V-Notch** \\ \hline  & (\(b_{0}\times h_{0}\times t_{0}\)) & (\(b_{1}\times t_{1}\)) & \(D\) **[mm]** & \(D\) **[mm]** & \(B\) **[mm]** & \(H\) **[mm]** \\ \hline KB1 & \(60\times 80\times 5\) & \(30\times  
In Eurocode 3 [4], there is an analytical formulation for calculating the joint resistance for joints without any vent holes. If the results from Table 5 are compared with the code predictions, the following facts become evident. For most of the joints, the results obtained using the code formulation exceed those obtained by simulation with the 3%\(b_{0}\) criterion with a mean deviation of 8.8%, but are lower than results obtained for the maximum load in the joint using the numerical model. When the predicted failure mode in the code is brace failure, the results of maximum load criterion are closer to the analytical formulation. In contrast, for the analyzed N-joints, when a different failure mode is predicted, the 3%\(b_{0}\) criteria showed a better agreement with the equations. Figure 10 shows in one graphic the three comparisons of maximum load in joints without any holes vs. those joints with circular, semi-circular or V-notched vent holes. In the same way, Figure 11 plots in one graphic these three comparisons of loads achieved by the joints, but in consideration of the 3%\(b_{0}\) indentation criterion. For the sake of greater clarity, Figure 12 presents this last comparison of loads in a bar diagram, allowing the identification of every joint considered in the study. From these three last figures, it is possible to point out that neither the hole presence nor the shape and position of the considered holes imply a significant strength reduction in the joints. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Type of vent hole**} \\ \hline  & \multicolumn{2}{c}{**Circular**} & \multicolumn{2}{c}{**Semi-circular**} & \multicolumn{2}{c}{**V-notched**} \\ \hline  & **3\%\(b_{0}\)** & **Max. load** & **3\%\(b_{0}\)** & **Max. load** & **3\%\(b_{0}\)** & **Max. load** \\ \hline Mean of deviation [\%] & \(-0.78\) & \(-0.45\) & \(-2.25\) & \(-1.30\) & \(-3.43\) & \(-1.91\) \\ Maximum deviation [\%] & \(-2.34\) & \(-1.2\) & \(-4.23\) & \(-3.23\) & \(-4.31\) & \(-2.69\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Deviations of loads for different vent holes with respect to joints without holes. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **Without** & **Circular** & **Semi-circular** & **Vnotched** \\  & **hole** & **hole** & **hole** & **hole** & **hole** \\
**Joint** & & & & & & & & \\  & & & &  
In addition to the presence, shape and position of the vent holes in the joint, some other variables were also analyzed to ascertain their effect on joint resistance. Therefore, it was observed that thicker brace thickness, \(t_{1}\), produced a predictable increase in the joint resistance, but also a different failure mode, changing from local buckling in the brace member to chord yielding. A bigger ratio between the widths of the brace and the chord--that is, the \(\beta\) ratio--implied higher joint resistance, as proposed by the Eurocode formulation. With respect to the influence of brace angle, it was observed that joint resistance decreases when brace angle increases, confirming prior studies [46]. Also, the predicted failure mode changed from brace failure to chord plastification in the case of brace angles of 60\({}^{\circ}\). In the case of the N-joints, the main parameter considered apart from the vent hole shape was chord thickness. The observed maximum loads achieved by the joints showed a clear increase with chord thickness. Figure 11: Comparison of load for a 3%b\({}_{0}\) indentation in joints with and without vent holes. Figure 10: Comparison of maximum load in the joints with and without vent holes.