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Experiences form the deconstruction of the Bridge Altstädter Bahnhof in the city of Brandenburg – Part 1: Investigation and findings on the announcement behavior of large‐format tendons with pre‐stressing steel susceptible to stress corrosion cracking The bridge "Altstädter Bahnhof" in the city of Brandenburg a. d. Havel was a large pre‐stressed concrete structure that provided an elementary traffic junction. In contrast to common pre‐stressed concrete structures with small tendons, large‐format pre‐stressing tendons were used in the longitudinal direction for the main superstructure. In the case of the present bridge, the tendon consisted of 392 oval strands made in the steel mill of Hennigsdorf, Germany, which are considered to be susceptible to stress induced corrosion cracking. During structural investigations, a high degree of embrittlement of the prestressing steel was detected, so that the bridge had to be demolished on May 19, 2021. Previously, in the area of detected prestressing strand breaks, longitudinal cracks appeared in the webs instead of the usual bending cracks. The different damage indication in the case of prestressing steel prompted the Federal Ministery of Transport to initiate further investigations. In cooperation with the Landesbetrieb Straßenwesen Brandenburg, the Hochschule für Technik und Wirtschaft Dresden and the Bundesanstalt für Materialforschung und ‐prüfung (BAM), experimental investigations were designed and carried out on site. Specifically, targeted damage to the large‐format tendon was carried out at two measuring points in order to reproduce and validate the damage pattern previously found. The concept, results from the investigations and findings for similar structures are the subject of the following first article (Part 1). The following part 2 will focus on the measurement methods and monitoring systems used during the experiments. [ABSTRACT FROM AUTHOR]

Carbon reinforced concrete – An alternative method for strengthening Concrete Bridges; Part 2: Strengthening of concrete bridges with carbon reinforced concrete – pilot project "federal highway bridges (A 648) across the river Nidda In 2020 two of three bridges, which are part of the german highway road A 648, were strengthened with carbon reinforced concrete for the first time in Germany. The two superstructures were erected in the 1970s as a pre‐stressed beam. As tendons a so called ‐sigma‐oval‐steel was used, which is sensitive for stress corrosion cracking. According to German guidelines and to exclude a sudden failure, it has to be verified if a damage of the tendons can be seen at the surface of the cross section via cracks along the superstructure. This ‐crack before failure‐ criteria was not fulfil for the described superstructures. With reference to the relevance of the bridges in the local infrastructure around Frankfurt a. M., a strengthening concept was necessary. Due to that fact, a strengthening with carbon reinforced concrete was identified as an economic and minimal invasive method. The report on that forerunner project is spread into three parts. The first part gives an overview about the bridges and the background on stress corrosion cracking, added with explanations about the planning steps. The following second part describes the strengthening with carbon reinforced concrete with focus on bridges. The third part goes further into detail, regarding the construction and the design of a carbon reinforced strengthening. [ABSTRACT FROM AUTHOR]

Am bereits 1851 dem Verkehr übergebenen Göltzschtalviadukt ergab sich im Rahmen der von der Deutschen Bahn geplanten Elektrifizierung des Streckenabschnitts Reichenbach-Hof die Aufgabe, den Brückenkopf in kürzester Zeit für die neuen Nutzungsanforderungen auszubauen. Über vergrößerte Auskragungen eines neuen Gleistragwerks sollte ein moderner Fahrweg hergestellt werden, welcher den vorgesehenen Geschwindigkeiten von bis zu 160 km/h gerecht wird. Gleichzeitig mussten die Voraussetzungen für die Anordnung von Oberleitungsmasten geschaffen werden. Neben einer Vielzahl von bautechnischen und baubetrieblichen Randbedingungen standen bei der Planung und Bauausführung die Aspekte der Denkmalpflege im Mittelpunkt. Hier ergaben sich im Spannungsfeld zwischen den Nutzungsanforderungen an einen modernen Fahrweg und dem Bestreben, bestehende Besonderheiten zu erhalten, interessante Kompromisslösungen. The renewal of the track supporting structure at the Göltzschtalviadukt - A 160 year old arch bridge with a new track for the electric railway Due to the planned electrification of the railway-track from Reichenbach to Hof by the Deutsche Bahn an enlargement of the bridge-head of the Göltzschtalviadukt had to be realised in a very short time. By using of a cantelivered structure the conditions for a modern track for speeds up to 160 km/h should been created. At the same time the space for the fastenings of the catenary masts had to be erected. In addition to a variety of construction and management constraints were the aspects of historic preservation at the center of planning and construction. From the conflict between the requirements of a modern infrastructure and the desire to preserve existing peculiarities resulted interesting compromise solutions [ABSTRACT FROM AUTHOR]

The bond behavior between reinforcement and concrete has a significant influence on the load‐bearing behavior and serviceability of the composite material. This paper focuses on the characterization of the bond behavior between fine‐grained concrete and mineral‐impregnated carbon‐fiber reinforcement. In this study, the influence of different bond lengths on local bond behavior was experimentally investigated. To predict the bond stress along the bond length, an analytical bond stress‐slip model was specified, and its model parameters were determined based on the experimental tests using an iterative approximation approach. Based on the defined bond stress‐slip model, a numerical bond model was developed and adjusted for the first time. A three‐dimensional (3D) finite element analysis (FEA) allows the simulation of the local bond stress along the bond length. Finally, the results of the 3D FEA were compared with the results of the experimental investigations to validate the developed numerical model. [ABSTRACT FROM AUTHOR]

This work was dedicated to the simulation of fiber composite structures consisting of carbon fibers and mineral impregnation. The aim of this study was to generate a micromodel that predicts the properties of a mineral-impregnated carbon fiber reinforcement. The numerical characterization was based on the discrete microscopic modeling of the individual phases using a representative volume element. In addition, the stochastic nature of the fiber strength, the anisotropic damage mechanisms of the brittle matrix, and the non-linear bonding behavior between the filaments and the matrix were considered in the material models. The material models were adjusted based on the literature sources and our own experimental investigations. This was followed by the validation of the representative volume element, quantifying the evolution of stiffness and damage under longitudinal tensile loading. The numerical results of material stiffness, as well as the tensile strength of the representative volume element, were compared with the results of the experimental investigations. To verify the robustness of the numerical model, significant model parameters were subjected to a sensitivity analysis. [ABSTRACT FROM AUTHOR]

Structural design and construction of a road bridge made of carbon reinforced concrete – Carbon reinforced concrete "The Next Step" In 2021, Saxony's first road bridge made of carbon reinforced concrete was built in Wurschen, a village located in the district of Bautzen in the east of Saxony. The new carbon reinforced concrete construction method is expected to help reduce both maintenance costs and the number of maintenance cycles for bridge structures while also increasing the service life compared to existing bridges made of steel‐reinforced concrete considerably. The high‐tensile carbon reinforcements, which are virtually fatigue‐resistant considering the applicable stress ranges, are predestined to be used in bridge construction due to their resistance to (reinforcement) corrosion. The design of the structure was based on the dimensioning and construction principles resulting from many years of research conducted by the Institutes of Concrete Structures at Technische Universität Dresden (TUD) and RWTH Aachen University. The construction work was carried out using the in‐situ concrete method and carbon surface reinforcement (carbon mats), carbon rod reinforcement, and standard structural concrete. Following the successful completion of the structure, load tests with an extensive measuring program verified the load‐bearing capacity of the carbon reinforced concrete road bridge. The structure was opened to traffic as planned in December 2021. [ABSTRACT FROM AUTHOR]

Aufgrund des schlechten Bauzustandes der alten Gewölbebrücke Ottendorfer Viadukt wurde zum Erhalt der Streckenverfügbarkeit der Bahnstrecke Riesa-Chemnitz die Erneuerung der Eisenbahnüberführung erforderlich. Entsprechend den gestalterischen und funktionalen Vorgaben wurde der Ersatzneubau als rahmenversteiftes Bogentragwerk mit einer Gesamtlänge von 90,95 m und einer Bogenstützweite von 74,95 m konzipiert. Den zentralen Bereich bildet ein Stabbogen mit einer an Flachstahlhängern aufgehängten Fahrbahn. Der Bogen durchdringt die Versteifungsträger und bildet mit ihm und den nach unten verlängerten Bogenstielen ein zusätzlich tragendes Rahmensystem. Aufgrund dieser komplexen Tragwirkung handelt es sich um ein außergewöhnliches Ingenieurbauwerk. Die ausgeführte Form des Bogentragwerkes wurde bei der Deutschen Bahn zum ersten Mal ausgeführt und präsentiert im Ottendorfer Tal eine äußerst ästhetische Landschaftsmarke. Der vorliegende Beitrag berichtet über die Konstruktion, die bauliche Umsetzung sowie ausgewählte statische Details des Brückenbauwerkes. The Ottendorfer Viadukt - Design and execution of an exceptional steel arch bridge. Due to the bad condition of the old railway arch bridge Ottendorfer Viaduct at the route Riesa-Chemnitz and to obtain the route availability the renewal of the railway overpass was required. According to the shape and functional specifications the bridge was designed as an arch structure stiffened by a framed substructure with a total length of 90.95 m and an arch width of 74.95 m. The central structure is formed by a bridge beam suspended from flat steel hangers connected with the overrunning arch. The arch is going through the bridge beams and forms with his stalks an additional supporting framed substructure. Because of this complex structural behavior the bridge is an exceptional engineering object. The special structure was carried out at the Deutsche Bahn for the first time and presents the Ottendorfer Valley with a highly aesthetic landscape mark. This paper reports on the design, the execution and selected static details of the bridge building. [ABSTRACT FROM AUTHOR]

Heiligenborn viaduct Historic railway viaducts define the cityscape or landscape. The fact that they actively shape and characterise the built environment and are considered important economic assets must, therefore, be taken into account for the restoration and further use of these testimonies of historic civil engineering. Such restoration measures are often accompanied by extensive enhancements of the structure's function. Apart from a simple widening of the track, additional technical installations such as overhead line equipment can have a significant impact on the viaduct's appearance. Thus, the restoration of heritage buildings and structures encompasses specific requirements for construction planning and construction work. [ABSTRACT FROM AUTHOR]

Innovative and sustainable replacement construction of concrete bridges The replacement construction of road bridges will gain enormous importance in the future. Since the reconstruction of bridges in Germany is almost exclusively carried out on site at present, it results in considerable traffic restrictions owing to the long construction times. The research project presented here and commissioned by the Federal Highway Research Institute shows ways to significantly reduce the construction time for the areas with traffic routes. A wide range of combination options is available for a variety of applications based on the use of separate solutions for the substructures, superstructures and toppings as well as the construction methods. The individual variants can be applied immediately as these are covered by the regulations. For the stringent application of prefabricated constructions, additional tolerance requirements need to be defined in the regulations. Research is still required for individual variants. The solutions developed can reduce on‐site construction time, and thus traffic restrictions, by up to 66 % and significantly reduce CO2 emissions. The increase in costs remains moderate. At the same time, future projects should also take into account external costs, as this will make the benefits of prefabricated construction even more apparent. An essential prerequisite for the implementation of the solution options shown is the general readiness to apply the modular construction method. [ABSTRACT FROM AUTHOR]

Abstract: Reinforcement made of carbon fiber reinforced concrete In the research project C3 – Carbon Concrete Composite new reinforcement systems made of carbon for concrete construction are developed. In that case, mesh‐like and bar‐shaped reinforcements are examined. Until now, these carbon reinforcements predominantly contain a plastic matrix that combines thousands of carbon filaments into one cross section. Scientists of the HTW Dresden and the TU Dresden are currently pursuing an approach to replace this plastic matrix with a mineral matrix to further improve the properties of the carbon reinforcement. In this paper, the basic principle of this new type of reinforcement for concrete construction as well as associated tests are presented. This should give an impulse for further research in this field. [ABSTRACT FROM AUTHOR]