**2.1 Maximum principal stress based fracture criterion**

The maximum principal stress-based fracture criterion is the simplest among all fracture criteria. It is useful to predict fracture behaviour of brittle materials under predominantly tensile loads. In this criterion, brittle fracture is expected to occur when the largest principal normal stress reaches the ultimate tensile strength (*σT*) of the material, which is usually obtained from tension tests of coupon specimens. The maximum principal stress-based fracture criterion is expressed as follows:

**Figure 2.** *Ductile fracture of a square tube under quasi-static crushing loads at -60°C [42].*

**Figure 3.** *Brittle fracture of a steel stiffened-panel under dropped-object impact at -60°C [44].*

**Figure 4.** *The axial-compressive collapse test set-up of a full-scale steel stiffened plate structure [1, 7, 8].*

$$\mathbf{Max}.(|\sigma\_1|, |\sigma\_2|, |\sigma\_3|) = \sigma\_T \tag{1}$$

where *σ*1, *σ*<sup>2</sup> and *σ*<sup>3</sup> are the principal stress components.
