Seismic fragility analysis of bridge response due to spatially varying ground motions

  • Received : 2015.07.22
  • Accepted : 2015.12.05
  • Published : 2015.12.25


The use of fragility curves in the design of bridges is becoming common these days. In this study, experimental data have been used to develop fragility curves for the potential of girder unseating of a three-segment bridge and a bridge-abutment system including the influence of spatially varying ground motions, pounding, and abutment movement. The ground excitations were simulated based on the design spectra for different soil conditions. The Newmarket Viaduct replacement bridge in Auckland was used as the prototype bridge. These fragility curves were also applied to the 2010 Darfield and 2011 Christchurch earthquakes. The study showed that for bridges with similar characteristics as the chosen prototype and with similar fundamental frequencies, pounding could increase the probability of girder unseating by up to 35% and 30% based on the AASHTO and NZTA seating length requirements, respectively. The assumption of uniform ground excitations in many design practices, such as the NZTA requirements, could potentially be disastrous as girders might have a very good chance of unseating (as much as 53% higher chances when considering spatial variation of ground motions) even when they are designed not to. In the case of superstructures with dissimilar frequencies, the assumption of fixed abutments could significantly overestimate the girder unseating potential when pounding was ignored and underestimate the chances when pounding was considered. Bridges subjected to spatially varying ground excitations simulated based on the New Zealand design spectra for soft soil conditions with weak correlation shows the highest chances of girders falling off, of up to 65% greater than for shallow soil excitations.


girder unseating;pounding;spatially varying ground motions;fragility curve;shake table testing


  1. Rossetto, T., D'Ayala, D., Ioannou, I. and Meslem, A. (2014), "Evaluation of existing fragility curves", SYNER-G: Typology Definition and Fragility Functions for Physical Elements at Seismic Risk, 27, 47-93, Springer, Netherlands.
  2. Sextos, A.G. and Kappos, A.J. (2009), "Evaluation of seismic response of bridges under asynchronous excitation and comparisons with Eurocode 8-2 provisions", Bull. Earthq. Eng., 7(2), 519-545.
  3. Shinozuka, M., Feng, M.Q., Kim, H.K. and Kim, S.H. (2000b), "Nonlinear static procedure for fragility curve development", J. Eng. Mech. - ASCE, 126(12), 1287-1296.
  4. Shinozuka, M., Feng, M.Q., Lee, J. and Naganuma, T. (2000a), "Statistical analysis of fragility curves", J. Eng. Mech. - ASCE, 126(12), 1224-1231.
  5. Standards New Zealand Technical Committee (2004), "Structural design actions Part 5: Earthquake actions - New Zealand" (NZS 1170.5: 2004), Wellington, New Zealand.
  6. Weiser, J. and Maragakis, M. (2013), "Seismic performance of highway bridges with seat-type abutments subjected to near-fault ground motions", Proceedings of the 2013 Structures Congress, 827-838, Pittsburgh, Pennsylvania, May.
  7. Wiebe, D.M. and Cox, D.T. (2014), "Application of fragility curves to estimate building damage and economic loss at a community scale: A case study of Seaside, Oregon", Nat. Hazards, 71(3), 2043-2061.
  8. Won, J., Mha, H., Cho, K. and Kim, S. (2008), "Effects of the restrainer upon bridge motions under seismic excitations", Eng. Struct., 30(12), 3532-3544.
  9. Zerva, A. (1991), "Effect of spatial variability and propagation of seismic ground motions on the response of multiply supported structures", Probabilist. Eng. Mech., 6(3), 212-221.
  10. Gur, S. and Ray-Chaudhuri, S. (2013), "Vulnerability assessment of container cranes under stochastic wind loading", Struct. Infrastruct. E., 10(12), 1511-1530. doi: 10.1080/15732479.2013.834943.
  11. Harichandran, R.S., Hawwari, A. and Sweidan, B.N. (1996), "Response of long-span bridges to spatially varying ground motion", J. Struct. Eng. - ASCE, 122(5), 476-484.
  12. Hwang, H., Jernigan, J.B., Billings, S. and Werner, S.D. (2000a), "Expert opinion survey on bridge repair strategy and traffic impact", Proceedings of the Post Earthquake Highway Response and Recovery Seminar, St Louis, Missouri, September.
  13. Hwang, H., Jernigan, J.B. and Lin, Y.W. (2000b), "Evaluation of seismic damage to Memphis bridges and highway systems", J. Bridge Eng., 5(4), 322-330.
  14. Japan Road Association (2002), "Design Specifications for Highway Bridges", Tokyo, Japan.
  15. Lagomarsino, S. and Cattari, S. (2014), "Fragility functions of masonry buildings", SYNER-G: Typology Definition and Fragility Functions for Physical Elements at Seismic Risk, 27, 111-156, Springer, Netherlands.
  16. Li, B., Bi, K., Chouw, N., Butterworth, J.W. and Hao, H. (2012), "Experimental investigation of spatially varying effect of ground motions on bridge pounding", Earthq. Eng. Struct. D., 41(14), 1959-1976.
  17. Li, B., Bi, K., Chouw, N., Butterworth, J.W. and Hao, H. (2013), "Effect of abutment excitation on bridge pounding", Eng. Struct., 54, 57-68.
  18. Chao, L., Hao, H., Li, H. and Bi, K. (2015), "Seismic fragility analysis of reinforced concrete bridges with chloride induced corrosion subjected to spatially varying ground motions", Int. J. Struct. Stability Dynam., 16, 1550010-1-1550010-27. doi: 10.1142/S0219455415500108.
  19. Nazmy, A.S. and Abdel-Ghaffar, A.M. (1992), "Effects of ground motion spatial variability on the response of cable-stayed bridges", Earthq. Eng. Struct. D., 21(1), 1-20.
  20. New Zealand Transport Agency (2014), "Bridge Manual (SP/M/022)", Wellington, New Zealand.
  21. Nielson, B. and Desroches, R. (2003), "Seismic fragility curves for bridges: A tool for retrofit prioritization", Proceedings of the 6th US Conference and Workshop on Lifeline Earthquake Engineering, 1060-1070, Long Beach, California, August.
  22. Nielson, B.G. and Desroches, R. (2006), "Seismic fragility methodology for highway bridges", Paper presented at the Structures Congress, St Louis, Missouri, May.
  23. Pang, Y., Wu, X., Shen, G. and Yuan, W. (2014), "Seismic fragility analysis of cable-stayed bridges considering different sources of uncertainties", J. Bridge Eng., 19(4).
  24. Ramanathan, K., Padgett, J.E. and Desroches, R. (2011), "Fragility curves for typical multispan simply supported bridge classes in moderate seismic zones: Pre- and post-seismic design considerations", Proceedings of the 3rd ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Corfu, Greece, May.
  25. Charvet, I., Ioannou, I., Rossetto, T., Suppasri, A. and Imamura, F. (2014), "Empirical fragility assessment of buildings affected by the 2011 Great East Japan tsunami using improved statistical models", Nat. Hazards, 73(2), 951-973.
  26. Chouw, N. and Hao, H. (2005a), "Study of SSI and non-uniform ground motion effect on pounding between bridge girders", Soil Dyn. Earthq. Eng., 25, 717-728.
  27. Chouw, N. and Hao, H. (2005b), "Evaluation of adequacy of Japanese code specifications on required bridge girders seating", Proceedings of the Australian Structural Engineering Conf., Newcastle, 11-14 September.
  28. Chouw, N. and Hao, H. (2008a), "Significance of SSI and non-uniform near-fault ground motions in bridge response II: Effect on response with modular expansion joint", Eng. Struct., 30, 154-162.
  29. Chouw, N. and Hao, H. (2008b), "Significance of SSI and non-uniform near-fault ground motions in bridge response I: Effect on response with conventional girder gap", Eng. Struct., 30, 141-153.
  30. Chouw, N., Hao, H. and Su, H. (2006), "Multi-sided pounding response of bridge structures with non-linear bearings to spatially varying ground excitation", Adv. Struct. Eng., 9(1), 55-66.
  31. Crewe, A.J. and Norman, A.J.P. (2006), "Experimental modelling of multiple support excitations of long span bridges", Paper presented at the 4th International Conference on Earthquake Engineering, Taipei, October.
  32. Dryden, G.M. (2009), The Integration of Experimental and Simulation Data in the Study of Reinforced Concrete Bridge Systems Including Soil-Foundation-Structure Interaction, University of California, Berkeley, California, USA.
  33. Elnashai, A.S., Borzi, B. and Vlachos, S. (2004), "Deformation-based vulnerability functions for RC bridges", Struct. Eng. Mech., 17(2), 215-244.
  34. GeoNet - Christchurch Earthquake. Strong Motion FTP Site (2011),
  35. GeoNet - Darfield Earthquake. Strong Motion FTP Site (2010),
  36. Gordon, P., Richardson, H. and Davis, B. (1998), "Transport-related impacts of the Northridge earthquake", J. Transportation and Statistics, 1(2), 21-36.
  37. AASHTO (2010), Load and resistance factor design (LRFD) specifications for highway bridges, American Association of State Highway and Transportation Officials, Washington D.C., USA.
  38. Abdel-Ghaffar, A.M. and Rubin, L.I. (1982), "Suspension bridge response to multiple-support excitations", J. Eng. Mech.Division, 108(2), 419-435.
  39. American Lifelines Alliance (2001), "Seismic fragility formulations for water systems, Part 1: Guidelines", American Society of Civil Engineers (ASCE) and Federal Emergency Management Agency (FEMA). Retrieved from
  40. Asteris, P.G., Chronopoulos, M.P., Chrysostomou, C.Z., Varum, H., Plevris, V., Kyriakides, N. and Silva, V. (2014), "Seismic vulnerability assessment of historical masonry structural systems", Eng. Struct., 62-63, 118-134.
  41. Basoz, N.I. (1999), "Statistical analysis of bridge damage data from the 1994 Northridge, CA, earthquake", Earthq.Spectra, 15(1), 25-54.
  42. Bi, K. and Hao, H. (2012), "Modelling and simulation of spatially varying earthquake ground motions at sites with varying conditions", Probabilist. Eng. Mech., 29, 92-104.
  43. Cavalieri, F., Franchin, P. and Pinto, P.E. (2014), "Fragility functions of electric power stations", SYNER-G: Typology Definition and Fragility Functions for Physical Elements at Seismic Risk, 27, 157-185, Springer, Netherlands.

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Supported by : Natural Hazards Research Platform