Fatigue life prediction of steel bridge connections using fracture mechanics models

Riveted connections used in steel bridges may be subjected to localized fatigue cracking. Experimental data were obtained from coupon fatigue tests for the investigation of the role of the riveting process on fatigue resistance. Fracture mechanics models of both open-hole and riveted A36 steel coupon specimens were used to predict the fatigue life. Stress versus the number of cycles to failure curves (S-N curves) were established based on empirical results and combined with Air Force Grow software (AFGROW) fatigue life estimates and compared. Fatigue crack growth test data was developed and compared with the material library in AFGROW. Fracture surfaces of the specimens were examined and striation spacing measured using Scanning Electron Microscope (SEM) images. Subsequently, stress intensity factors and local crack growth rates were estimated. Estimates of the local crack growth rates and the estimated stress intensity ranges were compared with data obtained from fatigue crack growth test results. Test results demonstrated that fatigue life was improved with the riveting process. In addition, accurate fatigue life predictions required consideration of the compressive residual stresses due to riveting.