**5. Computed results and discussion**

**Figure 19**, **Tables 7** and **8** present the comparison results between the test and the FE analysis. The difference of ultimate strength between them is 16.6% by the ductile material model, but it becomes at most 2.3% by the brittle material model.

**Figure 19.**

*Comparison of the load-axial shortening curves from the test and the FE analysis with the simplified brittle material model.*

*Ultimate Compressive Strength of Steel Stiffened-Plate Structures Triggered by Brittle… DOI: http://dx.doi.org/10.5772/intechopen.97155*


#### **Table 7.**

*Comparison between the test and the FE analysis with the ductile material model.*


#### **Table 8.**

*Comparison between the test and the FE analysis with the brittle material model.*

**Figure 20.** *Effect of weld metal on the ultimate strength behaviour.*

### *Low-Temperature Technologies and Applications*


**Table 9.**

*Effect of weld metal on the ultimate strength behaviour.*

When only the ductile material model was applied for all structure members without considering brittle fracture, the FE analysis overestimates the ultimate strength significantly. As the yield strength of the material at cold temperature is greater than that at room temperature, the ultimate strength becomes much larger as far as brittle fracture is not allowed to happen. On the other hand, the ultimate strength obtained from the FE analysis with the brittle material model is in good agreement with the test results. **Figure 20** compares the ultimate strength behaviour with or without the weld elements along the plate-stiffener junctions. It is seen from **Figure 20** that the weld metal model increased the ultimate strength by 4.7%. This is due to the mechanical properties of weld metal which are larger than those of base metal (**Table 9**).

**Figure 21** shows the deformed shape at the ultimate limit state of the tested structure obtained from the FE analysis without brittle fracture model (with only ductile material model). It is seen from **Figure 21** that the tested structure reached the ultimate limit state by tripping mode of stiffeners (without brittle fracture) which is similar to the collapse mode at room temperature [1]. However, the brittle fracture model represents brittle fracture behaviour which triggered the ultimate strength as shown in **Figure 22**, where deformed and fracture shapes of the test structures are compared between physical testing and FE analysis.

*Ultimate Compressive Strength of Steel Stiffened-Plate Structures Triggered by Brittle… DOI: http://dx.doi.org/10.5772/intechopen.97155*

**Figure 22.**

*Deformed shapes of the tested structure at the ultimate limit state obtained from the test and the FE analysis with brittle material model.*
