Three-dimensional Fracture Analysis of Large Opening Box Girder with Crack Damage under Bending and Torsion Loads

This work aims to investigate the complex fracture behavior of large opening box girder (LOBG) adopting three-dimensional (3D) finite element method (FEM). A numerical model is developed to simulate the fracture of LOBG under individually or jointly applied torsion and bending loads. The crack damage is introduced into both the side plate and bottom plate of LOBG. The influencing factors including crack lengths, crack angles, crack locations are also emphatically discussed. Besides, the crack growth angles are also predicted during the analysis. The results present that the large opening can generate significant effects on the crack propagation of the side plate crack (SPC) and bottom plate crack (BPC). Under the condition of torsion or hogging, SPC grows more easily than BPC, while BPC is relatively prone to grow under sagging condition. It is also found that the initial crack angles can obviously lower the stress intensity factor (SIF) under bending condition compared to torsion condition. Additionally, the cracks gradually approaching transverse frame are also more likely to induce mode I fracture under torsion condition. These findings from the present study can reveal insights for better understanding of fracture behavior for LOBG.