Enerpac Logo
Sign In

Box Girder Launching System on the I-95 Whittier Bridge


Walsh Construction


Amesbury, Massachusetts, USA


Constructed in 1951, the John Greenleaf Whittier Bridge is currently in the process of being replaced by a new bridge compliant with current safety standards. The high traffic bridge connects Newburyport and Amesbury via I-95 over the Merrimack River. Walsh Construction is employing a rail mounted gantry crane system to simplify the placement of the steel bridge girders and precast deck to create the approach spans. Two 6 foot tall, 960 foot long temporary support steel box girders will be launched across temporary piers to create a rail system for the gantry crane to operate on during the approach span construction. The steel box girder arrangement will be moved after the placement of each approach span. It’s critical that the two 550 ton temporary steel support box girders move in unison in order to prevent binding or misalignment of the gantry crane operating on top of the rail system.


Enerpac worked with Walsh to design a box girder launching system that would first clamp, then advance or retract the two separate box girders synchronously. The box girder launching system will be mounted at various temporary pier locations as the gantry crane moves to each stage of approach span construction. The custom launching solution is comprised of 4 custom long stroke RR-Series hydraulic cylinders for pushing/pulling, 8 custom RR-Series cylinders for clamping, and 2 custom 8000-Series hydraulic power units with networked controls for synchronized movement. Once the new northbound bridge span is complete, the system will then be utilized for the replacement of the southbound span.


RR-Series Custom Cylinder, EGM-Series Custom Pump