Probabilistic seismic demand models and fragility estimates for reinforced concrete bridges with Two-Column Bents

Jinquan Zhong, Paolo Gardoni, David Rosowsky, Terje Haukaas

Research output: Contribution to journalArticlepeer-review


Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of "explanatory" functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration.

Original languageEnglish (US)
Pages (from-to)495-504
Number of pages10
JournalJournal of Engineering Mechanics
Issue number6
StatePublished - Jun 1 2008
Externally publishedYes


  • Bayesian analysis
  • Bridges
  • Columns
  • Concrete
  • Deformation.
  • Seismic effects
  • Structural reliability

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint Dive into the research topics of 'Probabilistic seismic demand models and fragility estimates for reinforced concrete bridges with Two-Column Bents'. Together they form a unique fingerprint.

Cite this