# An Investigation on Base Metal Block Shear Strength of Ferritic Stainless Steel Welded Connection
## 4 Strength Comparison with Design Prediction and Recommendation  
### Comparison of Design Strength and Analysis Strength  
Table 4 summarizes the current block shear fracture design equations [2; 5; 22] and the block shear fracture shear strength equations proposed by other researchers [13; 14; 15]. In Table 4, \(Ant\) is the net area subjected to tension, \(Agt\) is the gross area subjected to tension, \(Agv\) is the gross area subjected to shear, \(Anv\) is the net area subjected to shear, \(\sigma_{y}\) is the yield stress, and \(\sigma_{u}\) is the ultimate tensile strength of STS430 material.  
Table 5 compares the predicted ultimate strength (\(Put\)) according to these equations with the analytical ultimate strength (\(Pua\)). The critical section areas of the tensile and shear fractures in the design block shear equation are shown in Figure 9. Equations (1)-(3) in Table 4 are derived from  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & KBC2016/AIS2016 & \(P_{n}=\sigma_{u}A_{nt}+0.6\sigma_{y}A_{sv}\) & (1) & The minimum value out \\  & \(P_{n}=\sigma_{u}A_{nt}+0.6\sigma_{u}A_{nv}\) & (2) & of the two strengths \\ \cline{2-4}
**Carbon Steel Welded** & EC3 & \(P_{n}=\sigma_{u}A_{nt}+\frac{\sigma_{y}}{\sqrt{3}}A_{mv}\) & (3) & \\ \cline{2-4}
**Connection** & Topkaya & \(P_{n}=1.25\sigma_{u}A_{gt}+\frac{\sigma_{y}}{\sqrt{3}}A_{gr}\) & (4) & Proposed equations by \\ \cline{2-4}  & Oosterhof and Driver & \(P_{n}=1.25\sigma_{u}A_{nt}+\frac{\sigma_{y}+\sigma_{u}}{2\sqrt{3}}A_{gr}\) & (5) & considering the stress \\ \hline
**Austenitic Stainless Steel** & [PERSON] et al. & \(P_{n}=1.35\sigma_{u}A_{gt}+1.15\frac{\sigma_{y}+\sigma_{u}}{2\sqrt{3}}A_{gr}\) & (6) & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Current design standards and equations by other researchers.  
Figure 8: Stress distribution for FT20L20 and FT30L77 in Paths 3 and 4: (**a**) Definition and symbol of the Paths 3 and 4 for FT20L20, (**b**) Tensile direct stress (S22) distribution for FT20L20 and FT30L77 in Path 3, (**c**) Shear stress distribution for FT20L20 and FT30L77 in Path 4.  
the results of the research on the block shear fracture of the bolted connections, and since the stress triaxiality effect, which is a characteristic of the welded connection on block shear strength, is not considered sufficiently, AISC2016/KBC2016 and EC3 underestimated the block shear strength by an average of 38% and 42%, respectively, when compared with analysis strength. The equation proposed by [PERSON] and [PERSON] [15] underestimated the block shear strength by an average of 22%. Although the Equations (4) and (6) proposed by [PERSON] [14] and [PERSON] et al. [13] estimated the strength of the ferritic stainless steel base metal fracture welded connection most closely with strength ratios (\(P_{ut}/P_{uu}\)) between 0.94-1.07 and 0.95-1.05, it is necessary to examine the block shear fracture mechanism considering the characteristics of ferritic stainless steel, which has different material properties from carbon steel and austenitic stainless steel (304 Type), as well as the stress triaxiality effect.