From an engineering standpoint, Poughkeepsie’s new Hoffman Street Bridge appears relatively straightforward: a 122 foot simple span steel bridge over the Metro-North railroad tracks just east of the Hudson River. However, its deceptively simple exterior belies a great deal of complexity; successful completion of the project required overcoming a number of intricate design and construction complications while maintaining a commitment to aesthetic integrity.
The original Hoffman Street Bridge, built in 1914, was a 97-foot two-girder span. The outdated through-girders extended seven feet above the roadway, seriously impeding drivers’ views at the approach intersections. The new span uses significantly lower profile weathered steel girders to improve intersection sight distance while meeting the clearance requirements of the tracks below. The original bridge had also been founded on the site where the underlying bedrock elevation was highest, yet misaligned with the existing approach roadways: in simple terms, the Hoffman Street Bridge did not properly align with Hoffman Street. Instead, taking Hoffman Street across the bridge meant following a zigzag route with poor intersection sight distances. The new bridge, sited 127 feet north of the original location, is far more streamlined. The bridge spans six working railroad tracks, which remained in use throughout both the demolition of the old bridge and construction of the new.
The initial designs for the Hoffman Street Bridge called for a foundation of spread footings on rock. However, preliminary field tests determined that the underlying bedrock had been fractured – most likely by late 19th century dynamite blasting during the construction of the railroad. Because of this discovery, alternative designs had to be investigated. Utilizing a single line of drilled shafts was determined to be the best solution due to their ability to resist the applied loads within a small footprint (thus helping minimize bridge span length) while also allowing the bridge to perform independently of the existing retaining walls used by the railroad, which passes below the bridge.
The aesthetic treatments chosen – weathering steel girders, a façade adorned with inlaid brick patterns, decorative lighting, and landscaping – all were context sensitive and in keeping true to the period feel of the earlier bridge, while also bringing a much needed face lift to an area that had become an eyesore.
The new bridge, completed in June 2013, has played a key role in the transformation of a Hudson River waterfront area in transition. With vehicle traffic more than tripled from 900 cars per day to a projected 3000, the bridge is central to the ongoing revitalization of a neglected industrial part of the city.
Dr. Barney Martin, PE (Project Principal)
Quentin Johnson, PE (Project Manager)
Blaise Blabac, PE (Lead Bridge Engineer)
James Sutton, PE (Bridge Engineer)
Thomas Cole, PE (Bridge Engineer)
Michael Bonadonna (Highway Engineer)
Richard Herd, PE (Resident Engineer)
Svitlana Loyk-McLaughlin (Office Engineer)
Daniel Bassanese (Chief Inspector)