Beton- und Stahlbetonbau最新文献

Am Ersatzneubau der Aurachbrücke an der Österreichischen A 1 Westautobahn zwischen Linz und Salzburg in der Nähe der Anschlussstelle Regau läuft derzeit eine Pilotanwendung für die Verwendung von einbetonierten faseroptischen Sensoren zur Unterstützung der Bauwerksprüfung. Das Bauwerk zeichnet sich nicht nur durch seine Abmessungen und verkehrstechnische Bedeutung, sondern auch durch das komplexe Bauverfahren aus. Der Spannbetondurchlaufträger mit Hohlkastenquerschnitt überspannt mit insgesamt sechs Feldern eine Eisenbahnstrecke, eine Landstraße, den Fluss Aurach und kleinere Straßen und Wege. Die Spannweiten betragen 72 m in den mittleren Feldern und 66 m in den Endfeldern. Im Zuge des Pilotprojekts wurde eine neue Technologie im Brückenmonitoring erforscht, die einen Paradigmenwechsel verspricht. Verschiedene faseroptische Messkabel wurden in der Schalung verlegt und einbetoniert. Mit diversen Geräten, die mit unterschiedlichen physikalischen Effekten arbeiten, wurden daran während des Baus und nach der Verkehrsfreigabe bei dynamischer Anregung sowie unter Verkehr faseroptische Dehnungs- und Temperaturmessungen durchgeführt. So konnten Vorgänge wie die Betonerhärtung, das Absenken des Traggerüsts, das Freisetzen der Pfeiler, der Vorspannvorgang oder die Überfahrt von Lkw nachverfolgt werden. Dehnungen und Rissbreiten werden auf der gesamten Kabellänge, auch in nicht zugänglichen Bereichen, gemessen und können so in Zukunft die Bauwerksprüfung wesentlich unterstützen. Im Forschungsprojekt konnten wertvolle Erkenntnisse zu den Vorund Nachteilen verschiedener Geräte und den Hürden, die bis zu einer breitflächigen Anwendung noch zu überwinden sind, gewonnen werden. Mehr dazu im Beitrag auf den Seiten 568–578. (Foto: AIT Wien)

Fibre reinforced polymer (FRP) reinforcement in compression

Due to their advantageous durability properties and high tensile strength, fibre reinforced polymer (FRP) reinforcements represent a serious alternative to conventional reinforcing steel. While the use of FRP bars, meshes, or stirrups for resisting tensile stresses is regulated in the DAfStb guideline “Nichtmetallische Bewehrung,” their application in compression is currently excluded by standards. This paper presents an experimental methodology for the determination of the compressive strength and elastic modulus of FRP reinforcement bars. In total, 95 tests were carried out on reinforcement bars made from glass, basalt, and carbon fibres. The results show a linear stress-strain behaviour up to brittle failure. Based on the results, partial safety factors are derived, enabling integration into the Eurocode design concept. In addition, design aids for centrically and eccentrically compressed cross-sections are developed, and a minimum reinforcement ratio is defined to prevent brittle tensile failure. The results of this paper will partly contribute to the second edition of the DAfStb guideline „Nichtmetallische Bewehrung“.

Potential stress corrosion cracking – condition assessment of the Elbe Bridge Bad Schandau Part 1: Special inspection, full closure and the path to reopening

The Elbe Bridge in Bad Schandau was constructed in the 1970s as an underslung girder bridge in reinforced concrete. Following the collapse of the Carola Bridge in Dresden, the Elbe Bridge—also considered susceptible to stress corrosion cracking—was subjected to a special inspection. Longitudinal and transverse cracks, as well as rust staining, were documented along the characteristic underslung tendon. As advanced damage due to stress corrosion cracking could not be ruled out, the bridge was fully closed, and a structure-specific damage analysis (OSA) was initiated. As part of the OSA, stepwise structural diagnostics, numerical verification and monitoring investigations were carried out. The results indicated signs of stress corrosion cracking and additional damage mechanisms, though only to a limited extent. Suspected causes were largely clarified or relativized with the aid of structural analysis. To detect future tendon or structural damage, a permanent monitoring system was developed and implemented. The applied methodology enabled a gradual rollback of compensatory measures. The Elbe Bridge Bad Schandau thus serves as an example for the assessment and management of existing bridges at risk of stress corrosion cracking.

Structural products and precast elements made of UHPC for strengthening of bridges

Ultra-High-Performance Concrete (UHPC) is characterized by outstanding compressive strength, durability, and formability, making it ideal for the strengthening and rehabilitation of bridges. UHPC components - such as hybrid anchor plates, truss elements (e.g., CoBeam), bridge bearings, and custom-fabricated anchorage or deviation blocks - can replace conventional steel or reinforced concrete parts. Advantages include compact design, reduced weight, enhanced durability, and significant CO₂ savings. UHPC allows for precise adaptation to complex geometries and is economically viable even in small quantities. A key factor in its practical use is product approval: in 2025, the first general technical approval (abZ) for UHPC components in prestressing systems was granted in Germany. This marks a milestone toward broader market adoption. The presented applications demonstrate UHPC's potential as an innovative and sustainable alternative to traditional construction materials. Future developments are expected to focus on standardization, which will facilitate quicker and more widespread implementation in bridge construction.

Assessing the compressive strength of concrete in existing structures

A probabilistic approach is presented to determine the characteristic values and the probability distribution of the concrete compressive strength based on (i) measurement data and (ii) information available from the design phase. The resulting characteristic value of the concrete compressive strength, $$, can be used for verifications acc. to the semi-probabilistic partial safety concept, while the probability distribution can be used for reliability analysis and further investigations. The approach is implemented in a freely available web tool.