INTRODUCTION

The New York City Department of Transportation (NYCDOT) Seismic Design Guidelines Report was updated in September 2008 by Weidlinger Associates to reflect current state-of-the-art knowledge and is under consideration by the New York State Department of Transportation (NYSDOT) to replace the December 1998 version. The NYCDOT seismic design guidelines are for use in the Downstate Zone which consists of New York City, Rockland County, Westchester County and Nassau County. NYSDOT has adopted the AASHTO (American Association of State Highway Officials) LRFD (Load and Resistance Factor Design) Seismic Design Specifications for the Upstate Zone. The NYCDOT Seismic Design Guidelines Report (September 2008) proposed for use in the Downstate Zone has some key differences with the current AASHTO LRFD Bridge Design Specifications. The outcome of this project will allow the Seismic Design Guidelines Report (September 2008) to be appropriately used with the AASHTO LRFD Specifications for the Downstate Zone leading to the promotion of a consistent statewide seismic design policy.

Specific objectives of this project are to:

1. Independently assess the effectiveness of the approach used in the New York City Department of Transportation (NYCDOT) Seismic Design Guidelines Report (September 2008) by evaluating the methodology and assumptions used in the development of the report and by critically commenting on the results of the report.

2. If the methodology and assumptions used are acceptable, develop Section 10 of the NYCDOT Seismic Design Guidelines Report into a form of New York State Blue Pages to be used with both the AASHTO LRFD Bridge Design Specifications and the AASHTO Guide Specifications for LRFD Seismic Bridge Design.

3. Determine the effects of adopting the NYCDOT Seismic Design Guidelines Report (September 2008) by developing examples of critical and essential bridges for soil types A to E and showing comparisons of results using NYCDOT (September 2008) report spectra curves to the results using spectra curves of the AASHTO LRFD Specifications.

4. Estimate the design and construction cost difference compared to the AASHTO LRFD Bridge Design Specifications incurred in implementing the NYCDOT Seismic Design Guidelines Report’s (September 2008) recommendations.