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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]

Copyright of Beton- Und Stahlbetonbau is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Copyright of Beton- Und Stahlbetonbau is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bautechnik is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Copyright of Beton- Und Stahlbetonbau is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]