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Soil-foundation-structure interaction modeling for probabilistic analysis of bridges

Funding: Rice University
Collaborators: Dr. Jamie Padgett,
Rice University
Zhenghua Wang

The increased failure potential of aging U.S. highway bridges, and their susceptibility to damage during extreme events, necessitates the development of efficient reliability assessment tools to prioritize maintenance and rehabilitation interventions. Reliability communication tools become even more important when considering complex phenomena such as soil liquefaction under seismic hazards. Currently, two approaches are widely used for bridge reliability estimation under soil failure conditions via fragility curves: liquefaction multipliers and full scale three-dimensional bridge-soil-foundation models. This paper offers a computationally economical yet adequate approach that links nonlinear finite element models of a three-dimensional bridge system, with a two-dimensional soil domain and associated one-dimensional set of p-y springs into a coupled bridge-soil-foundation (CBSF) system. A multi-span continuous steel girder bridge typical of the central and eastern United States along with heterogeneous liquefiable soil profiles is used within a statistical sampling scheme to illustrate the effects of soil failure and uncertainty propagation on the fragility of CBSF system components. In general, the fragility of rocker bearings, piles, embankment soil, and the probability of unseating increases with liquefaction, while that of commonly monitored components, such as columns, depends on the type of soil overlying the liquefiable sands. This component response dependence on soil failure supports the use of reliability assessment frameworks that are efficient for regional applications by relying on simplified but accepted geotechnical methods to capture complex soil liquefaction effects.  

Finite element model for the coupled bridge-soil-foundation system: coupled 3D bridge, and 2D soil model with 1D p-y springs (not visible between piles and soil elements) for 1D site response and liquefaction simulation.

  • Padgett, J.*, J. Gosh, and L. Dueñas-Osorio, (2010). “Sensitivity of Bridge Reliability to Parameter Variation in Systems Susceptible to Spatially Distributed Soil Liquefaction.” Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Management, Philadelphia, Pennlsylvania, USA, July 11 – July 15, 2010.
  • Aygun, B.*, L. Dueñas-Osorio, J. Padgett, and R. DesRoches, (2009). "Seismic vulnerability of bridges susceptible to spatially distributed soil liquefaction hazards . " Proceedings of the 2009 Structures Congress, Austin, Texas, USA, April 30 – May 2, 2009.