MIXED MODE FRACTURE ASSESSMENT FOR BOX GIRDER WITH CRACK DAMAGE UNDER COMBINED LOADS.

The box girder is an important structure widely used in the ship and marine engineering, but the fracture problem is not extensively investigated. The paper adopts the stress intensity factor (SIF) as the fracture parameter to perform the threedimensional (3D) mixed mode fracture assessment of the box girder structure with crack damage. The bending load, torsion load and side load are first introduced to study box girder fracture behavior. And the related influencing factors including crack lengths, crack angles and combined loads are investigated emphatically. Besides, the crack growth angle is also investigated to evaluate the crack propagation behavior. The results show that the load types have a significant effect on the crack propagation. The effect of bending load is generally greater than torsion load. The combined effect of bending and torsion loads may be considered adopting a linear superposition principle under transverse crack and larger angle crack. Additionally, the SIFs produced by torsion load only have a slight change with the increased crack angles. When the side load is added, the area near the crack upper surface will be easy to occur unstable expansion. These findings from the present study will provide a guiding significance to evaluate the crack propagation of box girder under combined loads. [ABSTRACT FROM AUTHOR]