Bridges
Abstract:
Seismic geotechnical investigations for a bridge involve several types of analyses, including: establishment of design level rock motions; site characterization and response analyses; ground and foundation motion computations; assessment of liquefaction and its impact on bridge foundations; soil-foundation interaction and impedance calculations; assessment of foundation performance under the design seismic loads; and in the case of existing bridges, if deemed necessary, design of seismic retrofit measures. The outcomes of each of these various investigations have important implications on the assessment of the overall vulnerability of a bridge. Frequently in engineering practice, “conservative” assumptions are employed at various stages of the investigations with the intent of ensuring that uncertainties are accounted for, and to allow the use of simplifying assumptions and analyses. Whereas a certain level of conservatism should be adopted in geotechnical engineering analyses under static loading conditions, a different approach is warranted for seismic loading conditions. In seismic geotechnical analyses, it is often difficult to discern what the impact of a particular assumption will be on the overall assessment of the vulnerability of a bridge. It is likely that in certain situations perceived conservatisms adopted in the seismic investigations may actually lead to an unconservative outcome. Thus, there are inherent pitfalls of perceived conservatism in seismic geotechnical investigations. Through examples of seismic geotechnical analyses of bridges, a case is made in favor of the application of a rational approach. The rational approach is to obtain accurate and site-specific geotechnical information, apply the analysis procedures that most accurately model the specific bridge site and foundations, and employ good professional judgment that is based on a thorough understanding of the fundamentals of soil, foundation and structural dynamics
Seismic Assessment and Retrofitting of the Brooklyn Bridge, New York, New York
INSIGHTS
A Faculty lecture to the Alumni of Northeastern University
May 31, 2007
by
Mishac K. Yegian
Photos and Related Documents:
Relevant Publications:
- Yegian, M. K. and Arzoumanidis, S., “Seismic Vulnerability Assesment and Retrofitting of the Historic Brooklyn Bridge”, Proceedings of the Japan-Greece Workshop, Kobe, Japan, October 2011.
- Yegian, M. K. and Arzoumanidis, S., Strohman, B. P., Kishore, and K., Patel, J. “Appraising the Brooklyn Bridge.” Featured Cover Article, Civil Engineering, ASCE, February, 2009, Volume 79, Number 2.
- Yegian, M. K., Arzoumanidis, S. Kishore, K., Patel, J., Jain, S. K., Strohman, B. P., and Edwards, N., “Seismic Soil-Foundation Investigation of the Brooklyn Bridge.” Proceedings of the ASCE-GI Earthquake Engineering and Soil Dynamics Conference, Sacramento, CA, May, 2008.
- Yegian, M.K., Jain, S.K., Kishore, K., and Patel, J. (2006) “Importance of Accurate Shear Wave Velocity in Seismic Evaluation of Bridges” 7th International Conference on Short and Medium Span Bridges, Montreal, Canada, August.
- Loukakis, K. and Yegian, M. K. (2004). “Quay Wall and Breakwater Design and Construction of the New Port of Patras”, Proceedings of the ASCE GeoTrans 2004 Conference, LA.
- Coates, A. Yegian, M. K., Kishore, K., Jain, S. Patel, J., Pizzi, J., Connolly, P., and Yin, B. (2004)“ Foundation Retrofit of the Third Avenue Bridge in New York” Proceedings of the ASCE GeoTrans 2004 Conference, LA.
- Yegian, M. K. (2004). “Seismic Geotechnical Investigations of Bridges in New York City”. Proceedings of the Fifth International Conference on Case Histories in Geotechnical Engineering, New York, NY, April.
- Ellman, R., Nikalaou, S., and Yegian, M. K. (2004). “Foundation Optimization and Design for Replacement of the Woodrow Wilson Bridge.” Proceedings of the Fifth International Conference on Case Histories in Geotechnical Engineering, New York, NY, April.
- Yegian, M.K. (2004). “Geotechnical Earthquake Engineering Applications to Bridges”. Proceedings of the ASCE NY Metropolitan Section Seminar on Performance Based Earthquake Engineering, Brooklyn NY, March 22-25.
- Yegian, M. K. (2003). “Seismic Geotechnical Investigations for Bridges,” Proceedings of the Central PA Geotechnical Conference, Hershey, Oct 29-31.
- Yegian, M.K., Arzoumanidis, S.,G., Nikolaou, S., and Cooling, T. (2002). “Seismic Soil-Foundation Interaction of the New Woodrow Wilson Bridge” Proceedings of the 7th U.S. National Conference on Earthquake Engineering, Boston, MA, July.
- Yegian, M.K., Gazetas, G. and Arzoumanidis, S.G. (1997). “Geotechnical Factors Influencing the Spatial Variability in Ground Motions for Bridges” ASCE Structures Congress, Oregon, April 13-16.