The new $1 billion Bang Na Expressway in Bangkok, Thailand, is not only the longest bridge in the world, but also represents the largest precasting operation ever carried out. The all-precast, prestressed concrete superstructure has a total length of 55 km (34 miles). This gigantic project provides an important link in the transportation system around Bangkok and is expected to play a major role in the commercial development of Southeast Thailand. The design solution was to use precast segmental, span-by-span construction. The box girders were match-cast and post-tensioned in place with dry joints and external longitudinal tendons. This article presents the design build contract, describes the design features of the bridge, discusses the construction techniques used in the project, and gives the details of the precasting operation.
