Prestressing Schemes for Incrementally Launched Bridges

Abstract

Incremental launching is a competitive construction method for medium-span prestressed concrete bridges. Compared with other techniques for in situ casting, in short bridges it is an alternative to the use of falseworks and reduces the cost of labor with the same investment. In longer bridges it is an alternative to movable shuttering systems and reduces both investment and labor cost. Compared with segmental precasting, it may reduce both investment and the cost of prestressing, which may be partial instead of total, with the same advantages in terms of industrial production. Due to its competitiveness and overall quality, this construction method is widely used in Europe. During launch, the superstructure is moved over fixed bearings. The superstructure dead load produces temporary flexural and shear stresses within the cross section that are quite different from those produced by the service loads and, consequently, require special prestressing schemes, thoroughly illustrated in this paper.