Award of Merit: Bridges

Riverside Drive Bridge over West 96th Street

The Riverside Drive Bridge over West 96th Street is a 1,110-sq.-ft. three-span steel structure that carries six lanes of vehicular traffic and two pedestrian sidewalks. But it needed a $4.7 million facelift to rehabilitate corroded structural steel and restore the bridge to its original beauty.

The judges called the project a success. "It's very hard to build an attractive overpass, but they've done it here," one juror said.

Originally built in 1920, the roadway portion of the bridge consists of reinforced lightweight concrete deck. Columns and struts of the exterior rigid frames are enclosed in massive architectural stone masonry work. The bridge, in a park setting within a residential neighborhood, is aligned northeast, crossing on a skew of 69 degrees.

advertisement

While the rigid-frame bridge underwent work in 1996 to repair the lightweight riveted structural steel components, a lack of funding left several elements untouched, including granite stone enclosed components of fascia girders, sidewalk portions of steel pan plate, railings and their bases, and sidewalk approach pavements. Those tasks became part of the job led by Gandhi Engineering Inc., the New York-based engineer and prime consultant.

Among the unique elements of the project was working with the mix of granite stone masonry and structural steel. The granite stone masonry hid the corroded load-carrying steel members from view, making them inaccessible for inspection.

One of the major construction tasks involved removing that granite stone masonry and the balustrade enclosures along the first and third spans in order to uncover encased corroded steel.

As the project team moved forward with work on the masonry, it kept uncovering more defective steel members, thereby increasing the scope of the work progressively. The rigid-frame spans measure 21 ft., 70 ft., and 21 ft. for a total length of 113 ft. Nine rigid frames line the bridge, spaced approximately 13 ft. center to center.

In completing this rehabilitative portion of the job, the project team had to erect new structural steel members and then had to reinstall the architectural stone masonry.

The job entailed other significant tasks, including installing new lightweight reinforced sidewalk concrete, new steel-faced concrete curbs, new tie-down steel anchor rods, new reinforced-concrete barriers on the two sidewalks, and new bridge railings. Lead paint removal and electrical work capped the extensive repair operation.