Marine Parkway-Gil Hodges Memorial Bridge

PROJECT OVERVIEW

This vertical lift bridge, which opened in 1937, spans across the Rockaway Inlet to Jamaica Bay connecting Brooklyn and Queens. The Marine Parkway bridge has a total length of 4,022 feet with a vertical lift section that is 150 feet long. When in the raised position, the lift provides a clearance of up to 57 feet. In 2006, 7.8 million drivers passed over the bridge. Additionally, the vertical lift portion was raised 157 times in 2006, allowing vessels to pass through the Rockaway Inlet.

Maintaining lifting capability is critical due to the presence of the U.S Coast Guard Station and a Sanitation facility in Jamaica Bay, as well as access to JFK Airport and other critical infrastructure. To preserve functionality, MTA requested our team protect the pulley cable sockets that anchor lift cables to the lifting girder. Because of this, the client’s vision and approach were to provide a steel box around the sockets to provide protection from tampering, fire and potentially explosive attack modalities. Notably, this bridge served as the primary route for emergency services during Superstorm Sandy to access Breezy Point which sustained major fire damage because of the storm.

Hinman showed that, in a severe vehicle fire, the steel covers added 5 to 25 minutes of fire resistance to the lifting mechanism.

HINMAN SOLUTION

Hinman used the Fire Loading and Mitigation Evaluator (FLaME), developed in-house for structural fire modeling. FLaME models the direct radiation from a hydrocarbon fire to the structural steel elements, as well as:

  • Re-radiation from the inside of the steel cover to the cables and cable sockets
  • Conduction from the steel cover, through the connections to the cable sockets
  • Convection inside the steel cover heating up the cables and cable sockets

Critical temperatures for the cables and cable sockets were evaluated based on the auto-ignition temperature of the lubricant. Hinman showed that, in severe vehicle fires, the steel covers added 5 to 25 minutes of fire resistance to the lifting mechanism. Once the steel covers had increased fire resistance of the lifting mechanism, Hinman collaborated with HDR’s mechanical and structural engineers to create a constructible method to install the covers. Overall, the final design met all the functional needs of the MTA, including:

  • Extent of covers governed by conflicts to existing structure
  • Swinging doors on span side of girder for accessibility
  • Removable hatches on tower side of girder for accessibility
  • Open sides and ventilation holes to allow for air movement
  • Holes at the bottom to allow for water drainage
  • Reduced steel thickness with intumescent paint to reduce weight
  • Wire mesh covering large openings to prevent bird nesting