Reliability analysis of tunnel-type anchorage in suspension bridge based on the second-order response surface method

In recent years, tunnel-type anchorage (TTA) has been increasingly applied in long-span suspension bridges. However, research on its reliability analysis under seismic effects remains insufficient. This study takes the Puli Bridge in Yunnan Province, China, as an example to investigate the dynamic response and reliability of the TTA of a suspension bridge under seismic action. The dynamic response of ten measurement points on the front and rear anchor faces of TTA under seismic acceleration was calculated and analyzed using finite difference method software. Combining the secondary sequence response surface method, the reliability indices of each measurement point on the anchor surface before and after TTA were calculated and analyzed, and the limit state equation of TTA dynamic response was established. The results indicate that the elastic modulus and cohesion of the TTA surrounding rock have a significant influence on the dynamic response of the TTA. The dynamic response of TTA decreases with increasing elastic modulus and increases with increasing cohesion. As shown in its displacement response. Due to the design characteristics of TTA, the reliability value of the front anchor surface is significantly lower than that of the rear anchor surface. Under different peak ground accelerations (PGA), the reliability of different crosssections of TTA varies and decreases with increasing PGA, indicating that the reliability of TTA is highly sensitive to changes in PGA. Research on the dynamic response and reliability of the front and rear anchor surfaces of TTA structures can provide reference and assistance for the seismic retrofitting and optimization design of TTA structures.