Sustaining Our Bridges: Taking Advantage of Captured Time By Paul K. Nolan, PE
The Burlington-Bristol Bridge is a steel-member, truss bridge with a vertical lift span. It crosses the Delaware River via Route 413 con- necting the City of Burlington in New Jersey to the Borough of Bristol on the Pennsylvania side. Built in May 1931, the bridge is situated between the Tacony-Palmyra Bridge (downstream) and the Delaware River-Turnpike Toll Bridge which sits upstream. Constructed of steel, the total length of the bridge is 2,301 feet (701.3 m), 20 feet (6.1 m) wide, and the longest span is 540 feet (165 m). The lift span is 61 ft. high when closed at mean high water and raises to 135 ft to allow large vessels to navigate the Delaware River. Project Program As part of the Burlington County Bridge Commission’s (BCBC) five- year capital improvement plan, the deck structure (viaduct) leading to the bridge span on the New Jersey side of the bridge was scheduled for replacement. The Bridge is a 2-lane crossing. In a perfect world, clos- ing both lanes and working only at night, the estimated time for repairs was about 30 overnight closures. However, due to weather or other unforeseen conditions, those 30 nights might not occur in succession, which could extend the project timeline. Closing only one lane would have subjected the steel-framed viaduct structure to vibrations caused by passing trucks which could also slow down the process. Working within these parameters with live traffic is the norm for roadway work- ers and comes with a mitigated risk. In addition, every time a work crew enters or exits a traffic zone to perform the work, including the set-up and break-down of traffic protection, it poses additional risk to their safety. Lighter than usual traffic patterns caused by the COVID-19 pandemic and the New Jersey Governor’s executive order mandating citizens to stay-at-home created a unique window of opportunity for the BCBC to rethink the project program. Taking full advantage of the situation, the BCBC approved completely closing-down the bridge for the shortest amount of time possible. This decision would maintain project conti- nuity and increase worker safety while causing the least amount of traf- fic disruption and inconvenience to the travelling public. On Thursday night June 18, 2020 the Bridge was closed for four consecutive days and nights. This time envelope also had a better potential success rate because projected weather reports for only four consecutive days are more reliable than scoping out longer periods. The construction would continue through Sunday June 21st, with a scheduled re-opening on Monday morning. Deck-off, Deck-on Staging Faced with new parameters, the Contractor Cornell & Company Inc., BCBC and Maser Consulting Engineers, hired to oversee the construc-
Full project scope showing the staging of the project. The removal of old decks progressed from south to north along the viaduct on the New Jersey side, toward the bridge tower span.
tion inspection and administration process, collaborated to completely re-think and coordinate the project orchestration. The overall program consisted of the removal of all the 40 ft deck sections on the viaduct on the south side bridge approach. The existing decks were methodically removed from the beginning of the viaduct in a south to north direc- tion, toward the bridge tower span. Once the deck removal process was far enough ahead to create a pre-established safety zone big enough for two cranes to safely function independently, the new deck installa- tion commenced following the same south to north path. This staging enabled two separate operational zones to function simultaneously, lifting decks on and lifting decks off, both toward the same goal. Once this tempo was established, the job progressed like clockwork. New deck installation consisted of pre-fabricated steel-member deck sections with pre-cast concrete assembled off-site. Once brought to the job site, they were stored and placed in unison next to bridge where rebar and sidewalks were installed prior to lifting.
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november 2020
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