Rapid Replacement of the Back River Bridge

This case study describes the design of a new bridge superstructure and modifications to an existing bridge substructure that carries a heavily traveled urban arterial just south of Boston, Massachusetts; an area with little tolerance for increased travel delays and almost no tolerance for construction. The Massachusetts Highway Department (MHD) required a rapid replacement design that did not involve experimental techniques or materials. What the MHD wanted was a new structure designed and built with known materials and techniques (in other words, "off the shelf technology"). The design consisted of using new steel stringers made composite with pre-cast concrete and steel gird deck panels, reconfiguring the existing 5 simple span arrangement into simple end spans and 3 span continuous middle spans, and using a two stage construction sequence. The design also included several time and cost saving ideas to live up to the FHWA's rapid replacement slogan "Get in, Get out and Stay out". This case study demonstrates how a little extra design time and cost can reduce construction time and cost. Considering the number of highway bridges that will need to be replaced in the near future, any opportunities to save time, money and reduce public inconvenience should be exploited.