Numerical study on the dynamic amplification factors of highway continuous beam bridges under the action of vehicle fleets

The mechanism and reasonable values of the dynamic amplification effect of highway continuous beam bridges under the action of vehicle fleets are quite complex and very unclear at present. This study, using 23 highway continuous beam bridges with the main span lengths from 32 m to 165 m as research objects, investigates the mechanism and influencing factors of the dynamic amplification factors (DAFs) of highway continuous beam bridges under the action of vehicle fleets based on the vehicle-bridge coupled vibration analyses. The results show that the travelling speeds and vehicle intervals (VIs) exert an important influence on the DAFs of continuous beam bridges. The maximum dynamic response at different travelling speeds and VIs is searched in this study, the maximum static response at different VIs is also searched, and their ratio is regarded as the effective DAFs. Based on the calculation results, it is concluded that when the roughness surface condition (RSC) is 'good' (or 'average'), the effective DAFs for the vertical displacement and vertical bending moment at the midspans can safely take a value of 1.15 (or 1.30); those for the vertical bending moment at the inner supports and shear force can safely take a value of 1.10 (or 1.20); and when the bridge fundamental frequency is less than 1.0 Hz, all DAF values can take a value of 1.05 (or 1.10). Meanwhile, the relevant provisions in AASHTO LRFD (2017) and CEN (2003) are considered on the safe side when RSC is 'good' or 'average'.