Parsons Corporation and HNTB Corporation
New York, New York

Seismic vulnerability studies are being performed on major bridges throughout New York City’s five boroughs. The first priority is “critical” crossings, bridges which are being evaluated and, if necessary, rehabilitated by their various owners to meet current seismic guidelines.

Haley & Aldrich served as the geotechnical consultant to Parsons Corporation on the main span and to HNTB Corporation on the approaches to the Throgs Neck Bridge, which carries Interstate 295 between the Bronx and Queens across the East River where it meets Long Island Sound. We analyzed soil and rock conditions underlying the bridge and its approaches and applied earthquake engineering modeling under various seismic events using ProShake™ software. We performed ground motion analysis and developed design spectra for the approach regions, as well as acceleration and displacement time histories, for each of the anchorage and tower locations for 500- and 2500-year earthquakes. We provided our soil- structure interaction output to project structural engineers, who were then able to create models that would help the owner in their decision on whether a bridge retrofit would be needed to meet seismic guidelines and, if so, what kind of retrofit would be appropriate.