The LT-Bridge consists of thin-walled box girders in the longitudinal direction and deck slab elements in the transverse direction. The box girders and the deck slab elements can be placed either with a launching gantry or with a pair of ground-based cranes. The box girders are connected longitudinally by post-tensioning tendons, continuity reinforcement and a small amount of in-situ concrete. Only the continuity reinforcement and the longitudinal reinforcement of the deck slab need to be installed on site. The box girders and the deck slab elements are connected with a layer of in-situ concrete placed on top of the deck slab elements. The LT-Bridge can be used in the span range from 30 m to 60 m. One span can be built per week.
The erection of one span of a multi-span post-tensioned concrete bridge is shown exemplarily in Fig. 1 to Fig. 3. In the first step two thin-walled precast girders are placed with the aid of two ground based cranes or a launching gantry (Fig. 1). In the next step deck slab elements are placed on top of the longitudinal girders (Fig. 2). The deck slab elements contain the top and bottom transverse reinforcement, the longitudinal bottom reinforcement and the shear reinforcement. On site only the longitudinal top reinforcement and the continuity reinforcement of the longitudinal bottom reinforcement have to be installed. The concrete of the deck slab is poured on top of the deck slab elements in two sections, as shown in Fig. 3.
An LT-Bridge requires less material consumption than a segmental bridge, while the construction speed is similar. Moreover, the number of high-maintenance bearings and expansion joints is reduced.
Photographs from a test on thin-walled precast girders, which was carried out recently at TU Wien, are shown in Fig. 4 and Fig. 5.