PIER B RETRACTABLE BRIDGE

Duluth, Minnesota

This retracting bridge was required to maintain boat access to the industrial slip where the developer constructed a transient marina offering water access to the hotel and restaurant guests.  This unique design utilizes a series of large roller assemblies and steel frames to encapsulate the bridge rails much like a rollercoaster.  All the steel support wheels are fully adjustable to fine tune the position and operation of the bridge.

The bridge is opened and closed by means of roller chain driven by a pair of gearboxes and electric motors connected to a common shaft.  Each gearbox and chain is designed to take the full load of the bridge to provide a redundant system in the event of a gearbox or chain failure.  Likewise, one gearbox and motor can be completely removed for maintenance and the bridge will still be operable. Integrating and concealing the mechanical components while still offering adequate maintenance access was accomplished through careful space planning and 3D modeling.

The bridge itself was designed to accommodate an emergency vehicle.  The historic appearance of railroad trestle was integrated into the bridge to recreate the industrial heritage of this unique waterfront property.   To maintain ADA compliance, NORDIC installed a 20ft long automated steel and timber ramp which is lowered by a linear actuator and a series of linkages to allow the bridge pass overhead while opening. After the bridge is closed, the ramp is automatically raised, to again, provide accessible access to the bridge. Both the bridge and access ramp was decked with 3-inch Douglas Fir planks sourced directly from Oregon.