Building bridges from thin-walled precast elements

Abstract

In the construction of Lafnitz Bridge and Lahnbach Bridge thin-walled precast concrete girders with an U-shaped cross-section were used in order to reduce the weight during the construction process. The usage of light-weight girders was advantageous because the girders were erected in the vertical position and rotated into the final horizontal position during the first application of the balanced lowering method. After filling of the girders with in-situ concrete the webs of the bridges were com- pleted. On top of the webs a deck slab was cast using a formwork carriage. While the application of the balanced lowering method permitted a fast construction of the webs, the production of the deck slab with a formwork carriage was a slow process. Therefore a method for the fast production of the deck slab was developed. In this new method precast slab elements, which are stiffened by cross-beams, are placed on top of the webs. This enables a fast construction of post-tensioned con- crete bridges with a plate girder cross-section.