Beton- und Stahlbetonbau最新文献

Track-bridge interaction on a railway viaduct with zero longitudinal restraint fastenings – Model and reality

To assess the track–bridge interaction (TBI) on a railway bridge zero longitudinal restraint rail fastenings, extensive analytical and experimental investigations were carried out on a 74 m long structure. The objective was to reduce additional rail stresses without altering the bridge's structural configuration. The applied track concept, featuring continuously welded rails longitudinally moveable on synthetic wood sleepers embedded in ballast, deviates from the standard design specifications and therefore required special approval on a case-by-case basis. Over a period of approx. 2 years, a combined long-term monitoring system was implemented, comprising geodetic and electronic measurements. The monitoring captured both temperature-induced deformations of the bridge superstructure and displacements and strains in the track structure. The data allow conclusions to be drawn about the activated longitudinal forces and the longitudinal restraint of the fastenings. The evaluation shows that train passages lead to a significant reduction in friction forces within the rail fasteners and that the modeled behaviour is plausibly reproduced. The findings provide valuable insights into the structural configuration of this special track design and establish a reliable data basis for the further development of the technical regulations.

Computational assessment of the Seseke bridge in accordance of levels 1, 2 and 4 of the guideline for computational assessment of bridges – nonlinear FE-calculations of prestressed concrete structures

As part of the upgrading planning of the bridges in North Rhine-Westphalia, a computational assessment of the Seseke Bridge near the city of Kamen was performed in accordance with the federal government's guideline for computational assessment of bridges. The bridge is a multi-web prestressed concrete construction from the 1970s. In the course of the computational assessment, almost all checks of the load bearing capacity and serviceability were satisfied. Only the shear capacity check in the area of the indirect support of the longitudinal girders remained deficient. Using a nonlinear FE calculation in accordance with level 4 of the guideline for computational assessment of bridges a hybrid verification derived from it, the load bearing capacity of the indirect support could be determined and the structure was successfully classified in accordance with DIN 1072.

Initial structural health monitoring of the nibelungen bridge in worms

The Nibelungen Bridge in Worms (NBW), constructed in 1953, serves as a pilot structure for the development and evaluation of innovative concepts in bridge preservation. Within the DFG Priority Program “Hundert plus,” a monitoring system was installed in 2023 to continuously record environmental conditions and structural responses in a selected pilot area. The primary objective is to establish a comprehensive database for condition assessment and lifecycle management of the bridge. This paper presents the monitoring concept, the implementation of the measurement system, and the user-oriented provision of data. Furthermore, two approaches for condition-based assessment are introduced: (1) a condition indicator for the qualitative assessment of corrosion risk in internal tendons and reinforcement based on condensation events within the box girder, and (2) a model-based method for realistic structural safety evaluation using a finite element model adapted to the actual structural behavior. Both approaches demonstrate the potential of structural health monitoring for lifecycle management of bridges, but also highlight the need for further in-depth validation to enable robust assessments.

Advances and Prospects of Distributed Acoustic Sensing for Bridge Structural Health Monitoring

Distributed Fiber Optic Sensing (DFOS) has become a well-established and reliable technique in structural health monitoring (SHM) of bridges. Among its applications, static strain measurements are most widely adopted, as modern fiber optic sensors and interrogators enable millimeter-scale spatial resolution of strain profiles along the sensor length. More recently, high-frequency measurements, known as Distributed Acoustic Sensing (DAS), have gained attention for capturing dynamic structural responses. DAS has been successfully applied to monitor road and railway traffic, investigate structural vibration under controlled excitation, and identify natural modes and resonant frequencies. Preliminary studies further suggest its potential to detect sudden, concealed damage events such as prestressing tendon breakage. This paper synthesizes recent advances and capabilities of DAS in bridge SHM, evaluates its benefits, limitations, and implementation challenges, and outlines prospective directions for broader integration of DAS into SHM practice.

Punching shear strengthening with concrete screws in combination with existing punching shear reinforcement

Not only for economic reasons but also to curb greenhouse gas emissions, the topic of structural strengthening and repair of existing concrete structures is becoming increasingly important. For several years, the Unit for Concrete Structures and Bridge Design at the University of Innsbruck has been investigating how the punching shear resistance of existing slabs can be easily and effectively increased using concrete screws. Based on numerous experiments and design rules developed on the basis of Eurocode 2, this strengthening method has been granted official building approval. However, the design approach included in this approval does not allow for the consideration of existing punching shear reinforcement. For this reason, additional punching shear tests were conducted, in which various types of punching shear reinforcement were combined with retrofitted concrete screws. The results of this test series are presented in this paper. A key finding is that the punching shear resistance of slabs already equipped with punching shear reinforcement can be significantly increased using concrete screws, indicating potential for incorporating this favorable interaction into the design approach.

Compressive strength of subtractively machined dry joints for connecting reused reinforced concrete components

The construction sector is one of the most resource-intensive industries in Germany and is responsible for over 50% of total waste generation. Current recycling strategies predominantly focus on the material recycling of demolition materials, which often leads to a loss of quality and landfill disposal. In contrast, high-quality product recycling of entire elements – especially reinforced concrete components obtained from demolished structures – has hardly been utilised to date but offers enormous potential for reducing waste, primary resource consumption, and CO₂ emissions. For the reuse of reinforced concrete components, the manufacturing and load-bearing capacity of the joints for a force-fit connection are of central importance. Dry joints offer advantages in this respect, enabling quick installation regardless of weather conditions and easy dismantling at a later date. A high-quality joint contact surface is essential for the safe transfer of compressive stresses. The quality of this joint contact surface is largely determined by the processing method used. This article examines two-part concrete test specimens with cut, milled and ground joint surfaces in terms of roughness, fitting accuracy and compressive strength. The results show that roughness has a significant influence on the compressive strength of subtractively machined concrete dry joints, whereas the effective contact surface has no clear influence.

Monitoring of the Kreuzhofbrücken in Munich at risk of stress corrosion cracking - conceptualisation and findings from experimental investigations

As part of a comprehensive monitoring concept, sensor systems for detecting prestressing steel breaks and assessing potential structural changes were installed and validated on two prestressed concrete hollow slab bridges in Munich. The combination of acoustic emission analysis (SEA), distributed fiber optic sensing (DFOS) and conventional measurement methods enables continuous monitoring and targeted evaluation of the structure. SEA functions as a real-time alert system for detecting wire breaks, while DFOS can record structural changes in detail. The system was supplemented by traffic load monitoring to determine site-specific traffic models, which lead to an improvement of the calculative warning behaviour of prestressing failure. The functionality and reliability of the sensor technology used have been confirmed by laboratory and in-situ tests. Results from experimental investigations during the dismantling phase also demonstrated that, for the cross-section of a hollow core slab with many webs, load redistribution in the transverse direction contributes to a redundant structural response in the event of tendon failure. The monitoring concept thus provides a basis for assessing the residual load-bearing capacity and for risk-based maintenance management.

Systemic quality management in concrete construction: Fundamentals, challenges, and perspectives

Concrete construction is a highly complex process characterized by irreversible execution steps and fragmented supply chains, placing high demands on quality management. In-situ concrete is considered a “special process,” as many critical properties can only be tested destructively or after completion, necessitating preventive and system-oriented control. This paper highlights the role of execution planning acc. to fib Bulletin 44 and the Systems Approach to Quality (SAQ), with particular consideration of international best practices, such as the methodology employed by DPR Construction. Key elements include the identification of Quality Creation Points (QCPs), interface management, checklists, project-specific guidelines, targeted training, and site inspections. Collaborative processes and digital tools such as BIM ensure consistent quality across fragmented supply chains. Application of these principles in Central European infrastructure projects, particularly in railway construction, demonstrates that a systemic, lifecycle-oriented, and collaborative approach enhances execution reliability, reduces errors, maintains schedules, and ensures durable, compliant, and cost-effective concrete construction.

Potential stress corrosion cracking – Condition assessment of the Elbe Bridge Bad Schandau Part 2: Planning, execution and evaluation of the load test

After the collapse of the Carola Bridge in Dresden in September 2024, similar bridges were subjected to special inspections. As a result, the Elbe Bridge in Bad Schandau, built in 1977, was closed due to the detection of cracks and the use of prestressed steel that was susceptible to stress corrosion cracking. Extensive diagnostic and structural analyses were carried out on the bridge. In addition, comprehensive monitoring measures were installed to observe the behavior of the bridge and possible deterioration processes, including acoustic emission monitoring (SEM), distributed fiber optic sensors (DFOS) and deformation monitoring. A load test was carried out to evaluate the resistance of the bridge and to determine the remaining prestressing force. Defined loads were applied using a self-propelled modular transporter (SPMT) and ballast weights. The structural reactions were recorded and evaluated against the values from the calculations. None of the limit criteria were reached during the test. The evaluation of the measurement data showed sufficient load-bearing capacity, so that the bridge could be approved for compensated traffic.

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Rohbaugrabung für das zukünftige Besucher–Informationszentrum im hochfrequentierten Sicherheitsbereich des deutschen Bundestages unweit des Paul-Löbe-Hauses in Berlin. Betroffen sind der derzeitige Mischwasserkanal des Regierungsviertels und die Trinkwasserversorgung des Reichstagsgebäudes. Das zentrale Element dieses Echterhoff-Projekts ist die Verlegung ist die Verlegung eines neuen, fast 500 m langen Mischwasserkanals in 3 m Tiefe aus robustem Polymerbeton. Die Arbeiten finden aufgrund der unmittelbaren Nähe zum Reichstag unter strengen Sicherheitsvorkehrungen statt (Foto: Echterhoff). Interview siehe S. A4 f.