In Anlehnung an das bei dem Bau der Argentobelbrücke angewandte Bogenklappverfahren wurde an der TU Wien ein Bauverfahren mit senkrechter Herstellung der Brückenträger entwickelt, um bei geeigneten Projekten Ressourcen, Kosten und Zeit zu sparen. Der Mechanismus zur Rotation der Brückenträger von der senkrechten Startposition in die horizontale Endposition erfordert den Einsatz von Druckstreben. Diese bilden in endgültiger Lage einen integralen Teil des Tragsystems und bewirken eine wesentliche Verkürzung der Spannweiten. Zur Reduktion des Aufwands für die Herstellung der Gelenkskonstruktionen entschied das Projektteam, dass die während des Klappvorgangs bewegten Teile (Brückenträger und Druckstreben) möglichst leicht sein müssen. Deshalb wurden in einem Forschungsprojekt an der TU Wien dünnwandige vorgespannte Fertigteilträger entwickelt. Im Zuge des Baus der Fürstenfelder Schnellstraße im Südosten Österreichs konnte das Brückenklappverfahren für die Brücken über den Lahnbach und die Lafnitz erstmals eingesetzt werden. Die in diesem Beitrag beschriebene Erstanwendung dieses neuen Bauverfahrens bei der Brücke über den Lahnbach konnte dank der guten Zusammenarbeit der Projektbeteiligten erfolgreich abgeschlossen werden. Mit der Erstanwendung konnte auch gezeigt werden, dass die mit dem Brückenklappverfahren errichtete Spannbetonbrücke mit 2,0 m hohen Brückenträgern beträchtliche Einsparungen an Ressourcen und Kosten im Vergleich zur ursprünglich geplanten Stahl‐Beton‐Verbundbrücke mit 4,2 m hohen Brückenträgern ermöglichte.

Continuous tunneling using a tunnel‐boring machine is a very popular method when it comes to the construction of large tunnel projects. The use of precast reinforced concrete elements, called tubbings, is a highly economical way to secure the tunnel post excavation. Unfortunately, a loss of the load‐bearing capacity has been observed in the past in the joints between the tubbings. Reasons for that are among others the required reduction of the cross section in the longitudinal joint area and, above all, the high normal compressive forces that arise due to soil pressure. This paper describes experimental testing of longitudinal joints of tubbings conducted at TU Wien. The increase of the load‐bearing capacity of a newly designed and optimized tubbing with high‐strength joint‐compressive reinforcement, which was developed and patented by the Institute of Structural Engineering at TU Wien, is presented. The high‐strength steel is characterized by its high yield strength of 670 MPa, as well as the very large available bar diameters of up to 75 mm. This new optimized tubbing enables the production of thinner tubbings compared to conventional designs, and can thus achieve a reduction in material, transport and excavation costs.

When building tunnels using segmental lining, the segmental lining takes over the supporting role of the excavated soil. With the workspace in tunnel construction being very constricted the circular, segmental linings are divided into small segments called tubbings which are assembled by a tunnel boring machine. This kind of construction results in numerous longitudinal and circumferential joints. The loading situation for the longitudinal joints is typically dominated by the compressive normal forces combined with relatively small bending moments. The thickness of the tubbings usually depends on the longitudinal joints of the individual segments. The cross‐sectional area of the tubbings has to be reduced at the joints in order to avoid spalling of the concrete leading to higher compression in the joints themselves. The Institute of Structural Engineering of TU Wien developed a new reinforcement design for tubbings with strengthened longitudinal joints. With a patent application pending, the newly designed joints were manufactured and tested demonstrating that the TU Wien proposal significantly increases the load‐bearing capacity of the tubbings in comparison to conventional tubbing solutions. The very satisfying results, obtained from the large‐scale tests of the newly developed joint design, show great potential for the construction of tunnels with thinner tubbings in the near future.

This new bridge construction method consists of building the bridge girders in a vertical position and of rotating the bridge girders into the final horizontal position. In order to rotate the bridge girders, additional structural elements, in this case compression struts, are required. In some topographical situations, it will be more efficient to produce the bridge girders with this innovative method than with the traditional incremental launching method or the balanced cantilever method. The span of the bridge girders is reduced by the compression struts, which enables considerable savings in construction materials. This article explains the design and the first application of the balanced lowering method to build two bridges across the Lafnitz and Lahnbach rivers as part of the Fürstenfeld Motorway in the southeast of Austria. The good cooperation of the project participants allowed for the successful first-time application of the method for the two bridges described in this article. The unproblematic application of the balanced lowering method for the prestressed concrete bridge with 2.0 m high bridge girders proved that considerable savings in resources and costs were possible compared to the originally planned steel-concrete-composite bridges with 4.2 and 4.6 m high bridge girders. K E Y W O R D Sbalanced lift method, balanced lowering method, post-tensioned bridge, precast concrete elements

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