In order to understand the overall picture, the different technologies for the use of thin‐walled prefabricated elements in bridge construction as well as the first‐time application of them in a bridge project in Austria are described in this paper. Thereafter a newly developed construction method for the on‐site fabrication of lightweight box‐shaped segments from thin‐walled concrete elements, strengthened with steel girders, is explained with the focus lying on the construction of a prototype in a 1:1 scaling. The conceptional design, the manufacturing in a prefabrication plant in Austria and the transport to a construction site are illustrated. Finally, an application example of the new technology is shown based on a design using the incremental launching method. The research confirms the feasibility of the on‐site assembly of segments from thin‐walled prefabricated elements and that this construction method, once minor constructive details will be solved in the ongoing research project, has great potential for a broad application in bridge construction.

A new bridge construction method, combining semi-precast elements and in situ concrete, has been developed at TU Wien, with the aim of decreasing erection time. In the course of construction using this new method, structural conditions arise that render a more detailed investigation necessary. By connecting a precast, thin-walled box girder to a bridge segment located on a pier by means of post-tensioning, a joint is created. By casting in situ concrete on the bottom and top slabs, the joint can be bridged with longitudinal reinforcement; however, the unreinforced vertical joints in the webs remain. This detail is a specific characteristic of the LT-bridge construction method and needs to be further investigated and assessed, as the question arises as to how this circumstance affects the torsional bearing behavior of the bridge superstructure. Torsion tests described in the literature consider ordinary box girders with longitudinal reinforcement or post-tensioned segmental bridges without longitudinal reinforcement at the joints. Therefore, the new reinforcement layout at the joints had to be investigated experimentally. Two large-scale thin-walled box girders—one without joints in the webs and the other with unreinforced joints in the webs—were tested, allowing for a direct comparison of conventionally manufactured bridges and those erected with the new bridge construction method. Furthermore, we investigated whether the results of common calculation methods corresponded to the experimental findings.

Various methods have been developed to produce deck slabs for steel–concrete composite bridges. Usually, the deck slabs are cast with in situ concrete using a formwork carriage, resulting in construction progress of 15 to 25 m of deck slab per week. A new construction method was developed at the Institute of Structural Engineering (TU Wien), which enables the swift erection of the concrete deck slab. This method employs precast deck slab elements with reinforced concrete cross-beams which span in the transverse direction. With this new construction method, producing up to two deck slab sections of 15–25 m per day becomes possible. Further, the performance of novel reinforcement detailing required for the precast deck slab elements is investigated by structural testing. The experiments consist of eight load-bearing tests on four specimens which represent sections of the element during casting and after completion. The investigated parameters in series 1 are the length and spacing of loops, used for protruding longitudinal bars enclosure. In series 2, the enclosure of the shear reinforcement and the height of the cross beams are varied. The results show that the targeted bending capacity could be reached in all tests with no signs of premature failure due to detailing reasons. Based on the experimental results, the feasibility of the new approach is shown and recommendations for detailing are given.

Am Institut für Tragkonstruktionen der Technischen Universität Wien wird derzeit an einem neuen Bauverfahren für vorgespannte Hohlkastenbrücken geforscht, wobei dünnwandige Halbfertigteile zum Einsatz kommen, die das Gewicht im Bauzustand erheblich reduzieren. Das geringste Eigengewicht wird bei der Verwendung einschaliger Wände für die Stege des Hohlkastens im Bauzustand erreicht. Diese Arbeit behandelt Untersuchungen zur Ergänzung von solchen einschaligen Halbfertigteilwänden mit Ortbeton, wobei drei Lösungsvorschläge, mit Spritzbeton, konventioneller Schalung und eine Lösung, die in ihrer Wirkung einer Doppelwand entspricht, präsentiert werden. Diese wurden praktisch erprobt, an Bohrkernen die Betonqualität untersucht und mithilfe zerstörender Untersuchungen wurde die Betonfestigkeit des Spritzbetons geprüft. Mit den Untersuchungen konnte gezeigt werden, dass große Einbauteile wie Hüllrohre und Stahlträgerflansche die Ausbildung von Spritzschatten bei Spritzbeton begünstigen und eine konventionelle Schalung neben einer Halbfertigteilwand praxistauglich, jedoch in der Ausführung aufwendig ist. Messungen zeigten den raschen Abbau des Frischbetondrucks beim Verfüllen einer Wand mit einseitiger Schalung. Durch das Verbinden von zwei Wandschalen ist eine Doppelwand sowohl aus statischer als auch aus baupraktischer Sicht stets zu bevorzugen. Wo das nicht möglich ist, sollten eine konventionelle Schalung oder Fertigteile mit einer Halbfertigteilwand verbunden werden, um dieselbe statische Wirkung wie bei einer Doppelwand zu erzielen.

<p>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.</p>