Marx Krontal GmbH

Hannover, Germany

Marx Krontal GmbH

Hannover, Germany
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Marx S.,Leibniz University of Hanover | Wenner M.,Marx Krontal GmbH
Proceedings of the 4th International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2015 | Year: 2016

Semi integral bridges are characterized by the monolithic connection between the superstructure and the piers. Thereby every element of the structure participate to the transfer of forces due to traffic loads. Simultaneously, high constraining forces due to thermal variation, creep, shrinkage or settlements appears. © 2016 Taylor & Francis Group, London.


Schacht G.,MarxKrontal GmbH | Bolle G.,UniveWismar University of Applied Sciences | Marx S.T.,Leibniz University of Hanover
Proceedings of the 4th International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2015 | Year: 2016

As a result of bad quality sealing, moisture and de-icing agents penetrated into pre-stressed hollow core slabs of the top floor in a freely exposed parking garage. Caused by the chlorides the slabs showed especially heavy damage in the support regions near the joints. The theoretical shear bearing capacity according to the technical approval of these slabs was strongly questionable because of the damage. With the help of an experimental loading test in-situ the influence of the damage on the shear bearing capacity of the slabs with different damage-levels could be determined. © 2016 Taylor & Francis Group, London.


Schacht G.,Marx Krontal GmbH | Bolle G.,Nurnberg University of Applied Sciences | Marx S.,Leibniz University of Hanover
High Tech Concrete: Where Technology and Engineering Meet - Proceedings of the 2017 fib Symposium | Year: 2017

In 2000 the Deutscher Ausschuss für Stahlbeton (DAfStb) published his guideline for load testing of existing concrete structures and therewith the experimental proof of the load bearing capacity became a widely accepted method in Germany. Since then over 2000 proof load test have been carried out and so a lot of experience exists in the usage of the Guideline. Nethertheless there are still reports about load tests carried out with mass loads or using mechanical measurement techniques. To prevent a misuse of the Guideline in future, to take into account the great experiences existing in the evaluation of the measuring results and the bearing condition, the DAfStb decided to revise the existing Guideline. In the last years there has also been an increased research activity focusing the development of evaluation criteria for possible brittle failures in shear and to extend the safety concept for the evaluation of not-directly tested elements. These results shall also be considered in the new Guideline. This paper gives an overview of the rules of the existing Guideline and discusses these in the background of the gained experience during the last 17 years. The new criteria for evaluating the shear capacity are explained. Also the thoughts of the new safety concept for load testing are introduced. © Springer International Publishing AG 2018.


Schacht G.,Marx Krontal GmbH | Bolle G.,UniveWismar University of Applied Sciences | Marx S.,Leibniz University of Hanover
Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016 | Year: 2017

As a result of bad quality sealing, moisture and de-icing agents penetrated into pre-stressed hollow core slabs of the top floor in an uncovered parking garage. Caused by corrosion the slabs showed especially heavy damage in the support regions near the joints. The theoretical shear bearing capacity according to the technical approval of these slabs was strongly questionable because of the damage. With the help of an experimental loading test in-situ the influence of the damage on the shear bearing capacity of the slabs with different damage-levels could be determined. Based on the results the amount of slabs that had to be replaced or could be repaired could be determined. © 2017 Taylor & Francis Group, London.


Schneider S.,Leibniz University of Hanover | Vocker D.,Marx Krontal GmbH | Marx S.,Leibniz University of Hanover
Beton- und Stahlbetonbau | Year: 2012

The fatigue behavior of concrete is mostly studied on the basis of constant amplitude tests. Constant maximum and minimum stresses are applied to concrete specimens during these tests. In addition, high loading frequencies are used in order to minimize the test duration. However, the loading frequency has an influence on the number of load cycles to failure. A study of fatigue tests documented in the literature has shown that the fatigue strength of concrete depends on the strain rate like the compressive strength due to single loading. With this consideration it becomes possible to convert test results with different loading frequencies into each other. Furthermore, a frequency limit can be determined depending on the stress range. Copyright © 2012 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Marx S.,Leibniz University of Hanover | Wenner M.,Marx Krontal GmbH
Beton- und Stahlbetonbau | Year: 2015

Semi-integrale Brücken sind durch die monolithische Verbindung zwischen dem Überbau und den Pfeilern gekennzeichnet. Dadurch beteiligt sich jedes Element des Tragwerks am Abtrag der Verkehrslasten. Gleichzeitig treten durch Temperaturänderungen, Kriechen, Schwinden oder Setzungen große Zwangskräfte auf. Diese Kräfte müssen beim Entwurf der Brücke besonders berücksichtigt werden und sollten durch eine vorteilhafte Verteilung der Steifigkeiten, insbesondere in den Unterbauten, reduziert werden. Der Bau von semi-integralen Brücken im Rahmen von langen Viadukten ist auch im internationalen Maßstab ein Novum. Um die Risiken im Zusammenhang mit diesem Bauwerkstyp, der noch nicht endgültig normativ geregelt ist, zu reduzieren und um Erfahrungen über die Berechnungsannahmen zu gewinnen, wurde vom Eisenbahnbundesamt eine umfassende Überwachung der Brücken gefordert. In der vorliegenden Untersuchung werden einige Ergebnisse der Langzeitmessungen an der Scherkondetalbrücke vorgestellt. Structural Health Monitoring of the Scherkondetalbrücke: a semi integral concrete railway bridge Semi integral bridges are characterized by the monolithic connection between the superstructure and the piers. Thereby every element of the structure participates to the transfer of forces due to traffic loads. Simultaneously, high constraining forces due to thermal variation, creep, shrinkage or settlements appears. These forces have to be accurately taken into account when designing the bridge and should be reduced through an advantageous distribution of the stiffness, especially in the substructure. The construction of semi integral bridges in the case of long viaducts is an innovation, also on international scale. In order to limit the risks associated with this non-definitively regulated type of structure and in order to collect experience about the calculation assumptions, the authorities required an extensive monitoring of the bridges. In this paper, a few results of the long-term measurements on the Scherkondetalbrücke will be presented. Copyright © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Schacht G.,Marx Krontal GmbH | Bolle G.,UniveWismar University of Applied Sciences | Marx S.,Leibniz University of Hanover
Bautechnik | Year: 2016

For 15 years load testing in Germany is regulated by the guideline of the Deutscher Ausschuss für Stahlbeton (DAfStb). Further research activity resulted in an improvement of the existing evaluation criteria. This and the introduction of the Eurocode into practice led to the need to revise the existing guideline. This paper summarizes the actual international rules for load testing and compares the different existing evaluation criteria. In addition to the description of the german standard, the actual development of the method of load testing in the USA is shown. Practical examples compare the German and American guidelines. It is concluded which requirements are demanded for the amendment of the guideline. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Schacht G.,TU Dresden | Muller L.,Marx Krontal GmbH | Curbach M.,TU Dresden | Marx S.,Leibniz University of Hanover
Beton- und Stahlbetonbau | Year: 2013

The paper describes the development of the shear design and the construction of reinforced concrete plates and compares the allowable shear stresses of the different previous code generations in Germany, with which the evaluation of the shear bearing capacity of existing concrete structures without shear reinforcement is possible. It is also shown on which basis the minimum value of the shear bearing capacitiy of elements without shear reinforcement according to DIN EN 1992-1-1/NA has been developed. Experimental investigations of the shear bearing behaviour of concrete slabs are evaluated. With the help of a code based shear valley a recommendation is given with which the danger of shear failure of reinforced concrete plates is excluded. Copyright © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Schacht G.,MarxKrontal GmbH | Bolle G.,UniveWismar University of Applied Sciences | Curbach M.,TU Dresden | Marx S.,Leibniz University of Hanover
Beton- und Stahlbetonbau | Year: 2016

Experimental Evaluation of the shear bearing safety The experimental evaluation of a reinforced concrete member with the danger of a brittle shear failure is yet not covered by the Guideline of the DAfStb for load testing because of the low ductile failure process. This paper describes the theoretical and experimental investigations carried out in [1] to allow a safe evaluation of the shear bearing safety in-situ. For a high resolution of the beginning failure processes a combination of modern measuring techniques was applied. The results of the experimental investigations are shown and discussed. Finally advises are given for the experimental evaluation of the shear bearing safety during load testing of reinforced concrete members. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

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