Investigation on the dynamic impact factor of a concrete filled steel tube butterfly arch bridge

Abstract This study introduces the dynamic impact factor (IF) assessment of a concrete filled steel tube (CFST) butterfly arch bridge with both experimental and numerical results. The modal parameters are identified from the measured accelerations and the IFs are computed from the dynamic strain responses. Four well-known bridge design codes are applied to assess the experimental IFs. A vehicle-bridge coupled vibration system is established to numerically investigate certain effects of vehicle speed, road roughness and structural damping on the IF. Both experimental and numerical results indicate that the IFs of distinct structural components vary significantly, suggesting that a uniform formula is insufficient to describe the impact effect of the whole bridge, which has been generally adopted in many bridge design codes. For the irregular shaped CFST arch bridge, the experimental method is currently the most accurate way to determine dynamic IF. New methodologies must be developed to support the engineers to design safer complex bridges and new formulations must be developed to be part of the bridge codes.