Evaluation of site factors for seismic bridge design in New York City area

Sissy Nikolaou*, George Mylonakis, Peter Edinger

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

11 Citations (Scopus)

Abstract

Site factors for seismic bridge design in the New York metropolitan area are evaluated. Several profiles from Brooklyn, Queens, and Manhattan, matching soil categories D and E as denned in the recent New York City Department of Transportation and NEHRP provisions, are analyzed using 1D wave-propagation theory. Dynamic soil properties are derived using state-of-practice correlations with standard penetration resistance and compared to available in situ geophysical measurements. Three different rock motions are used, each modified from real records to match 500-and 2,500-year probabilistic spectra for the region. Results are presented in terms of dimensionless ratios of surface and rock response spectra. The effect of impedance contrast between soil and rock on soil amplification is examined. It is shown that, although seismic hazard in the area is moderate, large surface motions can be generated because of strong site amplification effects that exceed those in the western United States. Derived spectra are compared with current design spectra defined in the 1998 New York City Department of Transportation guidelines and the 1995 New York City Seismic Code. Three issues that are not sufficiently addressed in existing codes are discussed: (1) deep sites containing thick layers of high-plasticity clay; (2) shallow sites with thickness <30 m; and (3) amplification of vertical ground motions.

Original languageEnglish
Pages (from-to)564-576
Number of pages13
JournalJournal of Bridge Engineering
Volume6
Issue number6
DOIs
Publication statusPublished - 1 Nov 2001

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