OWNER: NJTransit, Newark, NJ
DESIGN-BUILD-OPERATE-MAINTAIN CONTRACTOR: Bechtel Infrastructure Corp., Frederick, Md
DESIGN ENGINEER: Parsons Brinckerhoff, NYC
GENERAL CONTRACTOR: Agate Construction Co. Inc., Ocean View, NJ

By using Parallel Strand Lumber (PSL) for the Crosswicks Creek Bridge in Bordentown, N.J., the project team succeeded in devising an alternative to unavailable timber trestles.

This was one of many feats for a crossing that is part of New Jersey Transit's new 340mi. Southern New Jersey Light Rail Transit System (SNJLRTS) that will operate between Trenton and Camden, N.J.

Supporting both light rail transit and freight use, the new bridge replaced an existing timber trestle structure that was in poor condition.

In addition to this, the project team satisfied the community's concern with historical preservation. This was done by providing a bridge that resembles the original wood trestle structure while upgrading the freight train loading capacity and satisfying the current seismic design criteria.

The design-build contractor also mandated a constructible and economical design. This was done by using PSL for the trestle deck and for the timber bent caps.

PSL is a structural composite lumber made from small trees that are shaved into strips and glued together under high pressure. PSL provided the ability to have longer spans and an increased design life of up to 50 years.

In addition to providing for a 50-year design life, the bridge was designed to accommodate seismic and longitudinal freight train braking forces. These forces are quite large due to the length of the bridge and the presence of heavy ballast. The bents are flexible in the longitudinal direction so all of the longitudinal forces had to be carried back to the abutments.

The bridge also has an 800-ft. radius curve. Curvature of the alignment significantly added to the complexity of the design. Therefore, to simplify construction, the structure was laid out in chords. Each chord contains three or four 15-ft. timber spans with the steel span having its own chord.

The further simply construction, the bents supporting the main steel span and the abutments were rotated slightly so they would be aligned at 90-degrees to the structure. This made construction easier by eliminating the small skews at these locations.

To simplify fabrication of the structural members and minimize field drilling and trimming, all spacing of the deck items such as drains, connections, railing posts, through-bolts and ballast retainer supports, were standardized as much as possible.

The jury said, "the project team successfully implemented an alternative solution to the challenge of unavailable timber trestles. There were also many structural challenges the team overcame and they successfully integrated the bridge as part of the community."