Bang Na Expressway, Bangkok, Thailand - World's longest bridge and largest precasting operation

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.