Gefahr Spannungsrisskorrosion – Systematische Untersuchung des Brückenbestands in Mecklenburg‐Vorpommern

In diesem Beitrag wird die systematische Untersuchung des Brückenbestands des Landes Mecklenburg‐Vorpommern hinsichtlich seiner Gefährdung durch Spannungsrisskorrosion beschrieben. Das Projekt war in vier Phasen gegliedert. Zunächst wurde ein Konzept erarbeitet, danach aus dem gesamten Brückenbestand die gefährdeten Bauwerke herausgefiltert und in Kategorien bzw. Bauwerksgruppen eingeteilt. 16 besonders gefährdete Brücken wurden genauer untersucht. In der zweiten Phase wurden die Erkenntnisse aus dieser 1. Phase auf den gesamten Bauwerksbestand übertragen und eine Prioritätenliste erstellt. Außerdem fanden Beprobungen erster ausgewählter Bauwerke statt. Auf die Phasen 3 und 4, bei denen weiterführende theoretische Untersuchungen für spezielle Bauwerke im Vordergrund stehen, wird in diesem Beitrag nicht näher eingegangen. Hazard stress corrosion cracking – Systematical analysis of bridges in Mecklenburg‐Vorpommern. In this article, the systematic investigation of all prestressed bridges of Mecklenburg‐Vorpommern with regard to its exposure to stress corrosion cracking is described. The project was divided into four phases. First, a generally concept was developed. Then the endangered buildings were divided into categories. 16 bridges have been investigated. In the second phase, the findings from phase 1 have been transferred to all buildings in the stock and a priority list drawn up. In addition, first bridges were sampled. In the phase 3 and 4 were more theoretical studies and specific buildings in the foreground. These phases are not content of this paper.     

Brückenmodernisierung in Deutschland

Modernization of bridges in Germany – Motive and implementation. Currently, the Federal Government is responsible for the construction and maintenance of approx. 39440 bridge structures or 51360 partial structures in those cases where bridges are subdivided into a number of partial structures. Many of these structures have to carry loads that are several times higher than whatever seemed imaginable when the bridge was designed and built. For this reason, apart from maintaining their structural health, we must also strengthen them so that they are able to cope with future traffic volumes. Because of the great number of structures affected, in 2013, the then Bundesministerium für Verkehr, Bau und Stadtentwicklung (Federal Ministry of Transport, Building and Urban Development) joined forces with the Bundesanstalt für Straßenwesen (Federal Highway Research Institute) and the federal state road construction authorities to develop a ”Strategy for Strengthening the Road Bridge Stock on the Federal Trunk Roads“, which has since then been implemented. Of the more than 2,500 partial bridge structures mentioned there, whose inspection has been given priority, 46 % are currently being dealt with, which means that the structural design of the bridges is being assessed and the required construction work is being planned or realized. Around 20 % of the bridges envisaged for priority inspection have already been completed so that their load‐bearing capacity is now fit for the future. In terms of investment, top priority is thus given to the modernization of bridges. Bridge strengthening measures are financed from the ”Bridge Modernization Programme“. In the period from 2017 to 2020, around 2.9 billion euros will be available for this programme, which will be continued after 2020. The pledge that will be honoured is: Every modernization project that receives construction go‐ahead will be funded. Currently, there are 112 major bridge strengthening projects, each with investment totalling more than 5 million euros, which have been assigned to the Bridge Modernization Programme. A bridge deck area of more than 1.2 million m² will be upgraded in a sustainable manner by means of these projects, which include both new replacement bridges, reinforcement and ad‐hoc repair measures.     

Bemessungs‐ und Ausführungshinweise für Aufbeton auf Brückenfahrbahnplatten

Durch die ständige Erhöhung der Verkehrsbelastungen in den letzten Jahrzehnten und durch die Verwendung moderner Fahrzeugrückhaltesysteme sind ältere Brücken häufig nicht mehr in der Lage, ohne Verstärkungsmaßnahmen den Anforderungen des modernen Straßenverkehrs zu genügen. Eine bewährte Methode, die Tragfähigkeit einer Brücke zu erhöhen, besteht darin, auf das entsprechend vorbehandelte Rohtragwerk eine bewehrte Platte, welche mit dem Bestand kraftschlüssig verbunden ist, zu betonieren. Für die Bemessung sind der Eurocode und die in den europäisch technischen Dübelzulassungen (ETA) angegeben Bemessungsvorschriften (ETAG, TR, ...) anzuwenden. Der Anwender steht vor einer Fülle von breit gefächerten Wahlmöglichkeiten innerhalb dieser Vorschriften. Auf Basis der Erkenntnisse von mehreren Versuchsprogrammen gibt in Österreich die RVS 15.02.34 Anweisungen für die Fugenvorbereitung, die Rezeptur und den Einbau des Aufbetons und für die zugehörige Interpretation des Eurocodes und der Dübelbemessungsvorschriften bei der Bemessung der Schubfuge. Design and Detailling of Concrete Overlays Due to a permanent increase of traffic loads during the last decades and due to installation of modern vehicle restraint systems older bridges are often overloaded and thus have to be strengthened. Casting a concrete overlay on the existing structure is a state of the art method in order to increase the bearing capacity. The key is to prepare the interface in a way that no slip will occur between old and new concrete when forces are transferred over the interface. Mandatory for designing the concrete overlay is the Eurocode and in the European Technical Approvals (ETA) for dowels referred design guidelines (ETAG, TR, ...). However, the designer has to choose within a lot of options. On the basis of several research programs the RVS 15.02.34 gives recommendations for the preparation of the old concrete, the composition of the new concrete, casting and curing as well as choosing the associated options of the Eurocode within the structural design and detailing of the interface.