PROJECT HIGHLIGHTS: SARAH MILDRED LONG BRIDGE
The original Sarah Mildred Long Bridge, built in 1940, provides a regional link between Maine and New Hampshire, and is the critical back-up route in case of disruption on the Interstate 95 bridge. The new bridge alignment improves marine navigation by straightening the navigational channel, allowing larger ships to access the port and shipyard. With a larger 56' vertical clearance in its "resting" position, there will be 68% fewer bridge openings. In the normal operating, "resting" position, the bridge's lift span is at its middle level, allowing motor vehicles to cross the river. The new bridge's movable "hybrid" span lifts up to allow passage of tall vessels and lowers to railroad track level for trains to cross. 200' tall precast concrete towers will support the 300' long streamlined structural steel box girder lift span. The new bridge layout uses eleven (11) fewer piers than the existing bridge.
McNary Bergeron is providing construction engineering services to the contractor including:
- Longitudinal construction analysis of the two railroad and two vehicular precast balanced cantilever box girder approach superstructures.
- Geometry control system and coordinates for the precast approach superstructures and the precast main lift span towers.
- Erection manuals for the precast approach superstructures and the precast main lift span towers.
- Design of temporary works including cantilever stabilization falsework, end-span falsework, closure alignment beams and segment lifting assemblies.
- Integrated precast concrete segment shop drawings for 239 vehicular, 137 railroad and 88 tower segments.