Title:

Stage Road Bridge over Nighthawk Hollow Brook Replacement

The Stage Road Bridge over Nighthawk Hollow Brook has exceeded its useful design life. The bridge is one of two stream crossings along Stage Road in Gilmanton, New Hampshire. Built in 1930, and rehabilitated in 1960, the existing bridge consists of a steel stringer superstructure and a reinforced concrete abutment. The original stringers spanned 25’ with a paved width of approximately 23’-4”. A 2015 bridge inspection reported considerable spalling on the wingwalls, exposed rebar on the deck, substandard bridge rails, etc. Project sponsor, Hoyle, Tanner & Associates, has retained our project team to investigate alternatives and prepare a design. The proposed bridge doubles the span to 50 feet, and raises the bridge elevation over 2 feet, providing an adequate waterway opening for the new design flow. Rolled steel beams were designed for the superstructure which sit atop reinforced concrete abutments. Weak soil conditions on the site warranted the use of steel piles driven approximately 50 feet below grade to bedrock.

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