Impact of spatial variability parameters on seismic fragilities of a cable-stayed bridge subjected to differential support motions

Jian Zhong, Jong Su Jeon, Wancheng Yuan, Reginald DesRoches

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Abstract

Earthquake ground motions may vary significantly at multiple supports of long-span bridges, such as cable-stayed bridges, due to the incoherence, wave-passage, and site-response effects. To investigate the seismic vulnerability of these bridges, fragility analysis is performed using spatially variable ground motions. To achieve this aim, this study chooses a cable-stayed bridge with the most common configuration in China and creates a numerical model of the bridge, which can account for the inelastic response of its multiple components. Using the conditional simulation method, a set of unknown ground motions are simulated on the basis of a set of prescribed ground motions and characteristics of the target random field. The simulated acceleration time histories are then converted into the associated displacement time-histories to perform multisupport excitation analysis. Using the displacement time histories, a set of nonlinear time-history analyses are performed to generate demand models. The demand models are convolved with limit-state models to develop fragility curves. Moreover, the influence of spatial variability parameters associated with the incoherence, wave-passage, and site-response effects on the vulnerability of multiple components is examined in terms of damage-exceedance probability. The results indicate that the incoherency and site-response effects significantly affect the demands and corresponding component fragilities. The worst case corresponds to the combination of a firm-soft soil site and the largest incoherency drop parameter. The section ductility demands at the base of the pylon are significantly affected by the spatial variability of ground motions. However, it does not appear to produce obvious changes in the cable, the abutment, or the bearing displacement.

Original languageEnglish
Article number04017013
JournalJournal of Bridge Engineering
Volume22
Issue number6
DOIs
StatePublished - 2017 Jun 1

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Keywords

  • Cable-stayed bridge
  • Fragility curves
  • Incoherence
  • Site response
  • Spatially variable ground motion
  • Wave passage

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