Analysis on the Time‐Varying Fragility of Offshore Concrete Bridge

Abstract

For offshore bridges, the most prominent problem in the whole life cycle is that it is in an earthquake prone zone and an offshore corrosion environment at the same time. A nonlinear dynamic analysis model is set up for an offshore multispan and continuous rigid frame bridge based on the OpenSEES platform. The fragility surface of the bridge pier, bearing, bridge platform, and system are established by selecting a reasonable damage constitutive model of the material durability and a damage index analysis that studies the damage of the bridge durability to time-varying seismic fragility of bridge components and the system of the whole life cycle in offshore environment. The results show that the durability damage will lead to a constant decline in seismic capacity of the pier and an increase of the seismic demand under earthquake action as well as the probability to reach the ultimate failure state; compared to high piers, a low pier is more vulnerable to the offshore corrosion environment; the seismic fragility of bridge platform is higher than that of simply bearing; and the influence of offshore corrosion on environment is relatively large. With the prolongation of service period, the effect of durability damage on the seismic fragility of bridge system cannot be ignored in the coastal environment and it is necessary to make a reasonable evaluation on the seismic fragility of bridge structure during the whole life period.

Time-Variant Seismic Fragility of Offshore Continuous Beam Bridges Based on Collapse Analysis

“…Figure 4 shows that the mean value of the selected ground motion acceleration spectrum agrees well with the bridge design spectrum determined by "guidelines for seismic design of highway bridges" [39]. According to Equation (34), the PGA of 10 actual ground motion records are randomly generated into 10 groups of 150 ground motion records within the range of 0.01 g-1.0 g, and the PGA distribution is shown in Figure 5.…”

“…The corner and displacement deformations caused by bond-slip are simulated by the zero length section element, the consolidation of the pier top and beam is simplified to a zero length element. The detailed data of box girder, bridge pier and support are shown in Figure 3 [34].…”

“…where ag (i) (t) refers to the ground motion record after the ith amplitude modulation; a(t) refers to the original ground motion record; ki refers to the amplitude modulation coefficient. According to Equation (34), the PGA of 10 actual ground motion records are randomly generated into 10 groups of 150 ground motion records within the range of 0.01 g-1.0 g, and the PGA distribution is shown in Figure 5.…”

Comparison study of time-varying seismic fragility of precast segmental and cast-in-place bridge columns in high-speed railway bridges

“…The rust expansion cracking time of the concrete protective layer includes the initial corrosion time of the reinforcement and the migration and diffusion time process of the corrosion products. It can be expressed as follows (Liang et al, 2019):…”

Seismic Fragility Analysis of Multispan Continuous Girder Bridges with Varying Pier Heights considering Their Bond‐Slip Behavior

“…rough a comparative analysis of seismic fragility curves, bridges are more likely to be damaged as a system than any other component [10,11]. In reinforced concrete structures, the bond-slip between reinforcement and concrete has an important effect on the seismic performance of a structure.…”