Dynamic behavior and vulnerability analyses of steel-concrete composite beam bridge deck under rockfall impact
Here,aiming at threats of rockfall impact on upper structure of steel-concrete composite beam bridges in mountain areas,both dynamic behavior and vulnerability analyses of steel-concrete composite beam bridge deck were performed.Firstly,based on existing impact tests,a numerical simulation analysis method suitable for rockfall impacting bridge deck was proposed and verified.Secondly,a refined finite element model of a prototype steel-concrete composite beam bridge deck subjected to rockfall impact was established,and damage evolution processes,failure modes and dynamic responses of bridge deck and shear nail were analyzed.Furthermore,the sensitivity and influence laws of design parameters of concrete strength,longitudinal reinforcement yield strength,diameter and reinforcement ratio,transverse reinforcement ratio and stirrup ratio on the anti-rockfall impact performance of bridge deck were discussed.Finally,comprehensively considering geometric and material properties of bridge deck as well as the randomness of rockfall impact load,the vulnerability analysis of bridge deck was performed based on response surface method and Monte Carlo simulation.The results showed that increasing strength and reinforcement ratio of concrete can effectively enhance the performance of bridge deck to resist 400 kJ energy level rockfall impact;for the considered operating conditions,when rockfall velocity is 10-25 m/s,the ratio of peak deflection at mid span of bridge deck to deck thickness is less than 0.75.