Geostructural Project Detail

Driscoll Bridge, Garden State Parkway

Location

Perth Amboy, New Jersey

Client

PKF Mark III, Inc.

Services Provided

Geotechnical Design
Structural Design
Instrumentation

Project Overview

The Driscoll Bridge has a bridge span of about 4,500 feet from abutment to abutment and crosses the Raritan River. Working for the general contractor, Schnabel provided a range of geostructural engineering services. Work included design for a sheet pile wall along the main access road for construction, temporary shoring for the pile cap excavations, a pile load test frame capable of testing to loads in excess of 1,500 kips, pipe pile design for the trestle structure to support construction cranes, design and review of the Osterberg Cell load test for the drilled shafts constructed in the river, and design of load testing frames for large capacity piles.

Of particular interest was the development of the design for the drilled shaft reinforcing cage lifting system. These cages consisted of 36 No. 18 bars in dual concentric cages. With lengths of up to 100 feet and weighing about 700 lb/lf, handling these cages in one piece was a challenge to the contractor. Schnabel developed the lifting system including a cradle consisting of two Vierendeel-type trusses linked by light steel plates that served to brace the trusses as well as to support the rebar cage. This beam was analyzed using the finite element program SAP 2000. The cradle beam supported the entire length of the cage and allowed it to be rotated to near vertical on the barge. A lifting plate system was designed for attachment to the bars to then lower the entire cage into the shaft. By establishing a method of adjusting the length of the top plate attachment, the inner cage could be set to rest on the outer cage while concrete was placed.

Schnabel also provided the dynamic testing of the pipe piles and consultation of drivability issues including WEAP, CAPWAP and assessment of damaged piles.

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