Johann Kollegger

Balanced Lift Method for Bridge Construction

The new bridge construction method described in this paper involves building the bridge girders in a vertical position and rotating the bridge girders into the final horizontal position. The bridge girders can be built in combination with the pier using self-climbing forms, which allows for lower costs and a shorter construction time. The span of the bridge girders is reduced by the compression struts or tension ties, which results in substantial savings in construction materials compared to the balanced cantilever method for bridge construction. The method proposed was successfully applied in two field tests on bridge models with spans of 15 and 17 m. The first test involved the use of compression struts and in the second test the bridge girders were raised using tension ties. Results of the field test on the compression strut bridge are compared with a case study.

High Frequency Testing Facility for Stay Cables and Tendons

Fatigue is an important cause of failure in mechanical components and structures that are subjected to repeated loads. The testing of structural components under cyclic loading constitutes one of the most important fields of experimental mechanics. The testing of specimens with 2 to 20 million load cycles is only feasible for small specimens, and not for large structural elements. Usually, conventional servo-hydraulic testing machines are used; thus, time to carry out the experiments as well as the energy consumption increase dramatically with specimen size. A new approach to the testing of large structural elements by taking advantage of the resonance effect is shown in this paper. For example, a fatigue experiment on a stay cable for a bridge takes 3 to 4 weeks by using conventional servo hydraulic controlled jacks. The approach developed at the Institute for Structural Engineering at Vienna University of Technology reduces testing periods by a factor of 20 to 50 and the required energy input for a fatigue test by a factor of more than 1000. A testing unit dimensioned for a static tensile load up to 20 000 kN and an upper load for fatigue tests up to 10 000 kN was built at the Vienna University of Technology in 2006.

Assessment of Damaged Post-Tensioning Tendons

The actual condition and the durability of post-tensioning tendons in bridges built in the early years of prestressing are often questioned, as the ultimate strength of a bridge over its lifetime is not a constant but decreases with time due to different sources, mainly due to degradation of the post-tensioning materials. Many countries face the problem that some of their post-tensioned bridges have to be demolished because concerns regarding their ultimate strength are raised. Thus, the realistic assessment of existing structures of the ageing bridge stock within the national road and railway network is of enormous economic importance. In order to assess the influence of damaged tendons of a post-tensioning system on the ultimate strength of existing bridges more accurately, a series of tensile tests on damaged tendons, which were built using post-tensioning strands and wires from demolished bridges, was carried out.

Steel- Concrete- Composite Bridges with Innovative Prefabricated Slab Elements

The Institute of Structural Engineering of TU Wien is working on a new method for the construction of deck slabs for bridges, using partial-depth precast concrete elements with an in-situ concrete layer. Even though this construction method can be used for all types of bridges, the main focus for application is set on steel- concrete- composite bridges.

Comparison of Balanced Lift and Balanced Cantilever Method for the San Leonardo Viaduct

In recent years a new bridge construction method has been developed at the Institute of Structural Engineering of TU Wien. The so called Balanced Lift Method can be seen as an alternative to the Balanced Cantilever Method.

Balanced Lift Method—A New Bridge Construction Technique

The economic performance of concrete bridges can be improved in certain design situations by using the balanced lift method, a new bridge construction method developed at the Vienna University of Technology. This method proposes to build the bridge girders in a vertical position and to rotate them into the final horizontal position with the aid of compression struts. The compression struts decrease the span of the bridge and allow lighter bridge girders, compared to bridges built by the balanced cantilever method or incremental launching, to be obtained. The balanced lift method can be applied for bridges with high and low piers enabling the construction of bridges over deep or low valleys. The first application of the new method is the construction of two bridges with low piers for the Austrian road management company (ASFINAG) crossing the rivers Lafnitz and Lahnbach on the S7 motorway in the south-east of Austria.

Balanced Lift Method – Building Bridges Without Formwork

The balanced lift method is a building bridge method that was developed at the TU Wien. The most common methods to build bridges are the ones using falsework or the cantilever method, but a rather uncommon method, the lowering of arches is seen as the origin of the balanced lift method. The idea was to create a method which would allow a bridge to be built in a very fast manner without the usage of falsework, using prefabricated elements and mounting all parts together in a position – in this case vertically – that would simplify the construction process. In order to reach the final state of the bridge, the vertically assembled parts are rotated into their final horizontal position. This article contains a description of the development of the method, a large scale test will be portrayed and an already designed bridges using the balanced lift method will be shown.

Stress Redistribution in Prestressed Concrete Bridges Built with Ultra-Thin Precast Girders

The balanced lift method for bridge construction proposes to build the bridge girders in a vertical position and to rotate them into the final horizontal position with the aid of compression struts. During the construction process, when the bridge girders are rotated from the initial vertical position into the final horizontal position, it is of utmost importance for an economic application of the balanced lift method that the structural members are as light as possible. In a test beam (length = 30.02 m, height = 1.44 m, width = 0.7 m) the actual filling process with concrete was carried out. Subsequently, the longitudinal strains on the outside of the beam were monitored over a period of four years in order to investigate the creep behaviour. Due to creep, the initially high stresses in the prefabricated outer shell are gradually reduced and the in-fill concrete is subjected to axial compressive stresses.

Design of Bridges According to the Balanced Lift Method

The balanced lift method is a new bridge construction method. This method proposes to build the bridge girders in a vertical position and to rotate them into the final horizontal position with the aid of compression struts. The first application of the new method will be the construction of two bridges for the Austrian road management company (ASFINAG) crossing the rivers Lafnitz and Lahnbach on the S7 motorway in the southwest of Austria starting in 2013.

Überwachung, Prüfung, Bewertung und Beurteilung von Brücken

Unter Bauwerksprufung versteht man die Feststellung und Bewertung des Ist-Zustands einer Konstruktion. Unter Bauwerksuberwachung sind alle Masnahmen zusammengefasst, die erforderlich sind, um Mangel und Schaden an Bauwerken so rechtzeitig zu erkennen, dass ein Versagen ohne Vorankundigung ausgeschlossen werden kann. In diesem Zusammenhang ist ein Schaden eine Veranderung am Bauwerk, durch welche die Gebrauchstauglichkeit, die Dauerhaftigkeit oder die Tragfahigkeit beeintrachtigt wird, wobei die Ursache entweder in einem Mangel auf der Widerstandsseite oder einer Uberbeanspruchung der Konstruktion auf der Einwirkungsseite begrundet sein kann. Ein Mangel ist die negative Abweichung vom angestrebten Bauwerkszustand zum tatsachlichen Zustand. Ein Mangel kann einen oder mehrere Schaden zur Folge haben.