The Northampton Street Bridge has con- nected Easton, Pennsylvania, and Phil- lipsburg, New Jersey, across the Delaware River since 1806. FRP Composites Provide a Lighter Path for the Northampton Street Bridge By Scott Reeve
The historic Northampton Street Bridge connects two communities and two states.
The steel, cantilever truss bridge replaced a wood bridge in 1895 and has been repaired or rehabilitated many times during its almost 150- year history to safely accommodate evolving forms of travel. It un- derwent significant repairs in 1924, 1951, 1955, and 2001 with minor repairs in intervening years. During its 2020 inspections, the bridge was listed in “fair condition.” It was time for an update. Safe conduct for pedestrians was a core goal of the 2022-2023 bridge refresh project. But the sidewalk decking needed to fit the physical restrictions of this historical structure while meeting modern safety and performance standards. Composite decking, made from Fiber Re- inforced Polymer (FRP), met the challenge. Preserving History Project owner Delaware River Joint Toll Bridge Commission (DRJTBC) shared that “the project’s core objective is to extend the 125-year-old bridge’s useful life.” The Northampton Street Bridge is the only three-lane vehicular bridge in their bridge system and is the most heavily used non-toll bridge. Each day in 2019, the bridge bore an average volume of 16,900 vehicles across its three-ton weight limit and 15-mile-per-hour speed limit. History made this project a challenge; the bridge received its National Historic Civil Engineering Landmark designation by ASCE in 1995. Maintaining its structure was a core requirement of the project. But historic steel-truss bridges have weight restrictions that cannot meet the demands of modern vehicles or traffic. While the trusses provide great strength, the steel structures are also very heavy. This means that, compared to other bridge structures, steel truss bridges can accommo- date fewer vehicles before reaching total weight capacity. And structures like the Northampton Street Bridge that have cantilevered sidewalks face further weight restrictions from the additional sidewalk weight.
The DRJTBC needed to reduce bridge weight wherever possible with- out compromising safety, longevity or the historical integrity of the bridge. Composites provided a lightweight solution. On Firm Footing The Northampton Street Bridge project called for wider sidewalk deck- ing that worked with the planned steel structure without adding too much weight and that had built-in water control. Creative Composites Group (CCG) provided the project contractor, J.D. Eckman, Inc., with FRP composite panels to deck the sidewalks of the bridge. The prefabricated sidewalk panels don’t just meet design require- ments, including deflection and wind uplift loading. The panels also account for water control, and the CCG team included special details in the design like cover plates at the truss cut-outs, hatches and lamp post pedestals. FRP was a strong solution for this historic bridge due to its very high strength-to-weight ratio and its flexible sizes. “Many of us were skepti - cal how the installation and fitment of the panels would go, but we were
This cross-section view of the plans for the Northampton Street Bridge composite pedestrian sidewalk decking shows how the panel fits into the bridge structure.
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April 2023 csengineermag.com
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