Initial crack propagation of integral joint in steel truss arch bridges and its fatigue life accession

•An automatic crack propagation program based on ABAQUS has been developed, to simulate initial crack propagation at the most dangerous integral joint in a steel truss arch bridge.•The crack propagation rate is low in the early stage, which accounts for the main part of the remaining life in crack propagation.•The stress intensity factor is proportional to the initial crack size, while decreases significantly with the increase of gusset plate thickness. Integral joints are an important component in steel truss bridges. To investigate their initial crack propagation performance and assess their fatigue life, a finite element model of Bridge B as well as a local model of a steel joist with an integral joint are introduced. Subsequently, the stress–time curves of each component are transformed into equivalent stress amplitudes using the rain flow counting and Miner equivalent stress methods. Next, an ABAQUS automatic crack propagation program is developed to simulate the composite crack propagation at the most dangerous node, SE6. The results show that the crack propagation rate is low in the early stage of crack propagation; however, this process accounts for the main aspect of the remaining life in crack propagation. Finally, the effects of different initial crack sizes, nodal plate thicknesses, and initial angles of cracks on the stress intensity factor are investigated.