ABSTRACT
The LT-Bridge construction method has been developed in recent years at TU Wien. In this method, thin-walled longitudinal (L) girders made of high-strength concrete are combined with transverse (T) deck slab elements and subsequently connected by a layer of in-situ concrete. Compared to the conventional construction of multi-span post-tensioned concrete bridges with full in-situ concrete and temporary supporting structures, the LT-Bridge method enables faster construction and reduced material consumption. The Pinkabach Bridge, completed in 2022, was the first bridge built using this method. Currently, four additional LT-Bridges with lengths of up to 260 m are in the design phase in Austria. The structural design of LT-Bridges follows Eurocode 2. The webs of the thin-walled longitudinal girders typically have a thickness of only 120 mm, yet they must resist considerable shear forces and transverse bending moments that are mainly induced by traffic loads. The interaction formula for shear and transverse bending given in the new Eurocode 2 is conservative and leads to high quantities of stirrup reinforcement in the webs. To address this issue, the application of a layered shell element has been proposed for the design of the longitudinal girder webs. In this element, nonlinear material models are implemented according to Eurocode 2 for both the high-strength concrete C80/95 and the reinforcement (stirrups and longitudinal bars). This allows a realistic assessment of the load-bearing capacity under the combined action of shear and transverse bending moments. While the reinforcement of the webs in the Pinkabach Bridge was designed using the interaction formula of the new Eurocode 2, the LT-Bridges that are currently being designed can achieve further reductions in material consumption by applying nonlinear analysis with the layered shell element.
