Instandsetzung einer Betonbrücke mit Walzträgern nach dem Prinzip des Kathodischen Korrosionsschutzes

Für die Instandsetzung chloridbelasteter Stahlbetonbauwerke muss bei den so genannten konventionellen Verfahren oftmals Beton in großer Tiefe abgetragen werden. Dies verursacht hohe Kosten, stellt einen erheblichen Eingriff in das Bauwerk dar und führt nicht zuletzt zu Nutzungseinschränkungen während der Instandsetzung. Aus diesem Grund gewinnt der Kathodische Korrosionsschutz (KKS) von Stahl in Beton, eine zum Großteil zerstörungsfreie Instandsetzungsmethode, als wirtschaftliches Instandsetzungsverfahren korrosionsgefährdeter bzw.‐geschädigter Bauteile zunehmend an Bedeutung. Nachfolgend wird die Instandsetzung der Brücke über den Auer Mühlbach in München mit KKS beschrieben. Das Tragsystem der Auer Mühlbachbrücke besteht aus einbetonierten Walzträgern, die mit diskreten Einzelanoden geschützt wurden. Auf Grund der sehr hohen Überschüttung und der verkehrlichen Bedeutung dieser Brücke war der KKS besonders vorteilhaft anwendbar, da es während der gesamten Instandsetzung keinerlei Einschränkungen des Verkehrs gab. Repair of a Concrete‐Bridge with Rolled Section Beams applying the Principle of Cathodic Protection When repairing reinforced concrete structures containing chlorides by conventional methods, it is often necessary to remove the concrete to great depths. This causes high costs and leads to a significant intervention of the structure, combined with a limitation of use whilst repair measures. This is the reason why Cathodic Protection (CP) of reinforcement in concrete is gaining importance as predominantly non‐destructive, costeffective repair measure of structures susceptible to or damaged by corrosion. Consecutively the repair measure of the bridge over the Auer Mühlbach in Munich using CP is described. The load bearing system of the bridge of Auer Mühlbach consists of rolled section steel beams, which are protected using discrete anodes. Due to the high ground cover and the high importance to the intra‐urban traffic, the application of CP was in particular advantageously as the traffic has not been limited whilst the repair measure.     

Querkraftversuche an Spannbetonträgern mit carbontextilbewehrter Spritzmörtelverstärkung unter zyklischer Beanspruchung

Shear tests on prestressed concrete beams strengthened with carbon textile reinforced spray mortar under cyclic loading Many highway bridges in Germany exhibit shear capacity deficits under static and cyclic loading. A lot of structures are expected to demand refurbishment and strengthening within the next years, especially due to the current condition of many older road bridges in Europe. Different strengthening methods with specific advantages and disadvantages have proven to be suitable for the shear strengthening of bridges. In order to investigate the effect of an additional spray mortar layer with carbon textile reinforcement on the webs on the shear capacity, two tests on prestressed concrete beams were carried out at the Institute of Structural Concrete at RWTH Aachen University. The results of the tests were compared with previous tests on two identical beams which were not strengthened. The tests have shown that the strengthening measure leads to a considerably higher shear resistance concerning cyclic loading as well as the remaining static shear capacity.     

ÖBB Steyrtalbrücke – Belastungsprobe und Langzeitmessungen

ÖBB Steyrtalbridge – Load test and long term measurements At km 65,621 of the railroad track between Linz and Selzthal the Steyrtalbridge was rebuilt in the years 2013 and 2014. The essential design criterion from the client ÖBB Infrastruktur AG was the endeavor of an optimized bridge under consideration of life‐cylce‐cost, which among other things despite a bridge length of 182 m can be designed without high‐maintenance breather switches. Based on the current standards and certain design flexibilities, which are allowed in the codes special ways and techniques were used to calculate the rail tension. With this results of the rail‐structure‐interaction it was possible to design without breather switches. As consequence of the assumptions in the planning process it was necessary to make comprehensive measurements which shall give information of the real behavior of the bridge and compare them with the assumptions and results of the static calculation. Therefor static and dynamic load test were performed before opening to regular traffic. In addition long term measurements were carried out to evaluate the load‐bearing behavior over time and to confirm the calculation approaches for the verification of the rail‐structure‐interaction. In this article the planning of the monitoringsystem, the implementation and results of the load test and the following long term measurements are illustrated.