All-Precast Substructure Accelerates Construction of Prestressed Concrete Bridge in New Hampshire

This article describes a bridge project in New Hampshire that replaced two existing spans with a 115 ft (35.1 m) single-span precast, prestressed concrete box beam superstructure and precast concrete substructure. The Mill Street Bridge (Epping, New Hampshire) project integrated the use of high performance concrete (HPC) and precast/prestressed concrete components. The contract required the bridge to be assembled and ready for traffic in two weeks. The contractor accomplished the task in only eight days. This article focuses on the substructure details and how the project schedule, design, specifications, and contractual arrangements for a conventional bridge-replacement project are affected by specifying rapid bridge construction. The authors describe some of the reasons for the New Hampshire Department of Transportation’s (NHDOT) choice of rapid construction of bridges; these include minimizing construction-related traffic delays and improving work zone safety. The authors summarize with a list of seven conclusions: the precast concrete substructure detailed for use has promise; accelerated construction improves work zone safety; precast elements can be used to address labor limitations; accelerated construction minimizes construction related traffic delays on high volume roads; accelerated construction increases initial cost; grouted joints between precast elements should not be a weak link; and the best delivery concept may be to substitute precast substructure components for cast in place (CIP) elements. The article includes full-color photographs of the bridge project from beginning to completion.