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Trend of bridge collapses as reporting increases In recent weeks and months, there has been increased coverage of bridge collapses in the daily media. These concerned both collapses of bridges under construction and collapses caused by accidental events, such as floods, flash floods, impacts or fires, or under traffic loads. This clustered reporting suggests the question of whether the frequency of bridge collapses has increased this year and last. This paper will attempt to answer this question. To do so, both previous studies and current forecasts are summarized. In addition, a comparison of data from the IABSE collapse database with our own data collection was made. As a result, it cannot be said in principle that the collapse frequency of bridges has increased, but presumably the downward trend in collapse frequencies that has been observed for decades may have come to a halt. [ABSTRACT FROM AUTHOR]

Traffic Monitoring on a Highway Bridge – Data collection on local traffic characteristics as a basis for site‐specific traffic load models Developing site‐specific traffic load models for individual bridge structures based on local traffic data represents a potentially effective tool for existing road bridges with remaining calculative deficits when assessed according to current codes (guideline for assessment of existing structures, "Nachrechnungsrichtlinie"). A robust data basis to represent the local traffic characteristics is essential for this purpose. This paper presents investigations carried out during a long‐term monitoring campaign to comprehensively describe the traffic load on a selected bridge structure along Federal Highway A 92 over a period of one year. For the campaign, a measurement unit consisting of a laser scanner and a webcam, and structural monitoring with the application of bridge weigh‐in‐motion (BWIM), are used. Suitable strategies and concepts for collecting, processing, and evaluating all available measurement data enable a comprehensive collection of all parameters relevant for traffic load modeling and thus provide a data basis for detailed and realistic modeling of local traffic characteristics. Initial evaluations of the monitoring data for selected parameters and the comparison with otherwise typical assumptions from the literature in case of missing parameter information show partly significant differences to the extreme traffic characteristics underlying the load models in codes. [ABSTRACT FROM AUTHOR]

Debris flow actions on concrete bridge superstructures Bridge structures in alpine areas are subject to various hazards. These also include debris flows. Debris flows events demonstrably also lead to the destruction of bridges. In order to design bridges for such hazards, information on the impact force of debris flow is necessary. For debris‐flow impacts against piers, extensive miniaturized as well as real size tests are available. So far, no such tests are known for bridge superstructures. In this paper miniaturized debris‐flow impact tests on concrete bridge cross‐sections are presented. Based on the test results, recommendations for the design of concrete bridges in exposed locations are proposed. [ABSTRACT FROM AUTHOR]

Blast demolition of Salzbachtalbrücken During the planned conventional deconstruction of the Salzbachtal bridges, which were highway bridges of BAB 66 in the district Biebrich of Wiesbaden, a roller bearing collapsed on June 18, 2021. The superstructure laid on a pier and pushed it sideward; furthermore, cracks arose in the superstructure. As the structural safety could not be guaranteed, the bridge itself as well as the street Mainzer Straße and the Taunus railway line to Wiesbaden main station were closed. To clear the resulting significant traffic disturbance a blast demolition was planned and executed in a short notice. Due to the confined space and several infrastructure worthy of protection in the direct neighbourhood, the blast concept envisaged to blast the southern bridge by vertical collapse and to lay down the northern bridge by tilting collapse on the southern bridge afterwards. The blast demolition of both bridges was carried out on November 6, 2021 by 204 kg explosives. All piers of the southern bridge buckled to the west as planned and the superstructure fell down exactly vertically. The northern bridge followed 3 seconds later and tilted to the south. In this paper, the history of the original conventional demolition concept, the accident as well as the blast demolition concept and execution is described. [ABSTRACT FROM AUTHOR]

The structural condition as challenge for the deconstruction planning Until now no mandatory guidelines for the structural planning of the deconstruction of existing concrete structures are introduced by the authorities, which assist the planning engineers in the evaluation of these existing or damage structures. Often complex structural states of deconstructions have to be calculated, which depend on the knowledge of the actual structural condition. Therefore the only source of information is given by the existing documents, which often don't represent the actual state. To reduce the risks and to increase the planning and tender security, diagnostic investigations offer a big potential. Because not all information, as e. g. the knowledge about the possibility of a subsequent anchorage of cut prestressed tendons can be evaluated in advance of a deconstruction, further experimental investigations are necessary. As yet no technical or contractual rules are defined. The paper gives an overview of practical experiences and possible potentials of these experimental investigations. [ABSTRACT FROM AUTHOR]

KI/ML‐based Analysis and Interpretation of the IABSE‐Bridge Collapse Database Statistical analyses of bridge collapse data show that concrete bridges collapse significantly less frequently than bridges made of steel or wood. Since the main causes of bridge collapses worldwide are floods and associated fluvial processes, such as scouring, debris flows, etc. and impacts, it is reasonable to assume that the high dead load of concrete bridges leads to an overall more robust behavior in these events. This paper will examine whether the IABSE collapse database confirms this hypothesis and whether indications of further causes can be identified. For this purpose, the IABSE collapse database is examined using artificial intelligence and machine learning (AI/ML) methods. However, the AI/ML analysis does not confirm the previous thesis. The reasons for the rejection of the thesis, such as the representativeness of the data, are also discussed. An extension of the database for events with large numbers of collapses is recommended. [ABSTRACT FROM AUTHOR]

Renewal of reinforced concrete bridges by means of UHPFRC Ultra‐High‐Performance Fiber‐Reinforced Cementitious composite building material UHPFRC is a novel building material that is characterized by high mechanical strength and durability. UHPFRC is suitable for the renewal of existing reinforced concrete bridges. Based on the experience with numerous applications, the basic design concepts for the protection, rehabilitation and strengthening of reinforced concrete bridges are developed in this paper. These relate to the improvement of durability as well as the strengthening of bridge deck slabs and girders. The implementation in practice of the design concepts is illustrated by three recently completed projects. It is shown that the renewal of reinforced concrete bridges with the help of UHFB is also important with regard to the sustainability, since the material resources already installed in the reinforced concrete structure are reused. [ABSTRACT FROM AUTHOR]

Gemeinhin gelten die französischen Bauunternehmer FRANÇOIS‐MARTIN LEBRUN (1799–1849) und FRANÇOIS COIGNET (1814–1888) als Pioniere des modernen (Stampf‐)Betonbaus im Hoch‐ und Brückenbau. Der vorliegende letzte Teil der Artikelserie zur frühen Geschichte des modernen Betons zeigt jedoch, dass diese Protagonisten des neuen Baustoffes bereits auf etablierte Verfahren und erprobte Techniken zurückgreifen konnten, auch beim Bau von Bogenbrücken und gewölbten Hochbauten. Außerdem wird der Blick geweitet auf Ingenieure des deutschen Sprachraums, die ebenfalls schon um die Mitte des 19. Jahrhunderts mit Gewölben und Bogenbrücken aus Beton experimentierten. Der Beitrag spannt den Bogen jeweils von frühen Beschreibungen und Abbildungen in zeitgenössischen Publikationen bis zu erhaltenen Zeugnissen des Wölbens mit Beton. Dabei wird auch deutlich, dass die Grenzen zwischen einer Betonbauweise, wie wir sie heute kennen, und einem unregelmäßigen Bruchsteinmauerwerk lange fließend blieben. On the early history of modern concrete – part IV: Arches and vaults The French contractors FRANÇOIS‐MARTIN LEBRUN and FRANÇOIS COIGNET are generally considered “fathers” of modern concrete, particularly with a view to bridge building. However, when they embarked on their careers, they were already able to draw on considerable previous French experiences. The present article, the last one of a series of papers dedicated to the early history of concrete, puts the well‐known achievements of LEBRUN, COIGNET and others in context. The paper also traces the development of concrete between rough rubble‐cement masonry and real concrete in the modern sense. For all the different variants of concrete vaulting and bridge building, the article spans the entire scope from early notices in contemporary publications, to preserved monuments, including some little‐known examples. [ABSTRACT FROM AUTHOR]

On the introduction of post‐tensioning forces into thin‐walled box girder cross‐sections In the course of a research project currently being conducted at the Institute for Structural Engineering at the TU Wien, box girder cross‐sections consisting of thin‐walled semi‐precast concrete elements are being investigated for their use in bridge construction. The box girder cross‐sections are assembled segment by segment on the construction site and tensioned together with external post‐tensioning to form a self‐supporting bridge girder. Subsequently, the web, floor and deck slabs are completed with in‐situ concrete, thus producing a monolithic structure without joints. The post‐tensioning of the thin‐walled box girder cross‐section poses a particular challenge. In this paper, a new approach to the introduction of post‐tensioning forces in thin‐walled box‐girder cross‐sections is presented, based on experimental investigations carried out and their analysis with a nonlinear FE calculation. Two different manufacturing methods of the blisters were investigated, on the one hand a prefabricated construction method and on the other hand a cast‐in‐place method. It has been shown that the production of blisters as precast elements is preferable for the introduction of post‐tensioning forces into thin‐walled box girder cross‐sections due to the shear joint created by the in‐situ concrete construction method. [ABSTRACT FROM AUTHOR]

Transferability between input variables of life cycle cost analyses for concrete bridges Life cycle cost analyses are a method for prioritizing structures and measures in the context of building maintenance management. Life cycle cost analyses take into account a large number of different input variables, which in turn are themselves based on different parameters, because often infrastructure and real estate operators do not have all input variables available. This paper deals with the transferability of the different input variables and parameters in order to be able to perform a homogeneous life cycle cost analysis. For this purpose, a literature review and a subjective estimation of cross‐correlations were performed. [ABSTRACT FROM AUTHOR]

New method for fatigue verification of existing road bridges using monitoring data For road bridges, the fatigue verification based on Eurocode can be carried out in general with the simple fatigue load model ELM3 and the damage equivalence factors λi allowing to avoid using the complex fatigue load model ELM4, which consists of five vehicle types. However, this application is limited. For example, bridges with spans or influence lines outside the interval [10 m–80 m] cannot be verified. Furthermore, a fatigue verification based on monitoring is presented in order to calculate and evaluate the damage equivalence factor λ1 for the monitoring data. Based on the current fatigue verification according to Eurocode, this paper presents a method for fatigue verification using the vibration response of bridges. This method is developed in order to calculate the damage equivalence factor λ1 for all bridge spans as well as for all monitoring spectra without any limitation. [ABSTRACT FROM AUTHOR]

On the completion of single‐panel semi‐precast walls with in‐situ concrete The Institute for structural engineering of TU Wien is currently developing a new construction method for prestressed box girder bridges, using thin‐walled semi‐precast elements that considerably reduce the weight during construction. The smallest selfweight during construction is achieved when using single‐panel walls in the web of the box girder. This paper deals with investigations on the addition of in‐situ concrete to such single‐panel semi‐precast walls, presenting three proposed solutions, with shotcrete, conventional formwork and a solution that corresponds to a double wall in its effect. These were tested in practice, the concrete quality was examined on drill cores and the concrete strength of the shotcrete was tested with the help of destructive tests. The investigations showed that large built‐in components such as ducts and steel girder flanges favour the formation of spray shadows with shotcrete and that conventional formwork next to a semi‐precast wall is practicable but costly in execution. Measurements showed the rapid reduction of the fresh concrete pressure when filling a wall with formwork on one side. By connecting two panels, a double wall is always to be preferred both from a static and a practical construction point of view. Where this is not possible, conventional formwork or prefabricated elements should be fixed to the semi‐prefabricated wall to achieve the same static effect as with a double wall. [ABSTRACT FROM AUTHOR]

Modular bridge structures made of carbon fibre reinforced ultra‐high performance concrete Graph‐based design and trajectory‐sensitive manufacturing In order to enable the prefabrication of bridge structures in a continuous production line, extensive changes in design and execution are necessary. Therefore, this paper explains a holistic and end‐to‐end digital design process for a modular construction system that composes planar, additively manufactured modules. The system is computationally represented with a graph‐based data model, laying the foundation for design automation employing graph rewriting rules. Sets of rules are employed to generate modular structures according to two approaches: Either existing component geometries are segmented, or rules formalize the aggregation of structures. At this process state, predominantly geometric information is available. This information is developed into a semantically rich representation of the decomposition until a highly detailed production model for each module can be instantiated parametrically. Because of the flexible definition based on NURBS, the production model can depict a variety of possible joining situations and connections. Beyond this, the model is the basis of the printing path generation for the additive manufacturing process. The path is determined according to the principal stress directions, numerically interpolating the results of a non‐linear FE analysis. Along this printing path, the alignment of carbon fibre reinforcement is steered by custom nozzle technology, enabling outstanding material properties of the manufactured components. [ABSTRACT FROM AUTHOR]

Development of a modal based bridge monitoring system In recent years, the interest in modal based monitoring systems, especially for bridge constructions, has increased significantly. The aim is to detect damage processes at an early stage and to extend the service life of existing bridges and to minimize maintenance costs. The modal parameters, natural frequencies and mode shapes, are global parameters that depend on the stiffness and mass distribution of the structure. Assuming that damage processes are accompanied by a decrease in stiffness, they allow the detection and localization of damaged areas of a structure. In the context of this paper, laboratory tests are presented, in which the sensitivity of the modal parameters to increasing crack formation was investigated. In addition, the pre‐damaged reinforced concrete beams were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) laminates and subsequently loaded until failure. A high sensitivity of the modal parameters with respect to increasing crack formation can be detected. Moreover, the effect of the amplification system can be successfully proven by means of the modal parameters. [ABSTRACT FROM AUTHOR]

Reassessment of existing structures based on measured data – Part 2: Structural reliability analyses using NDT results Every decision about the reliability of a structure is associated with uncertainties. The reassessment of existing structures remains a major challenge. The decisive difference compared to the design of new structures is the possibility and necessity to collect individual information about the actual condition and properties of the structure. Such knowledge should be appreciated in the reassessment in order to reduce uncertainties and increase the validity of the results. Reliability analyses using measured data require the comparability of measurement results and the evaluation of the quality of the measured information. Both requirements can be met by adequate measurement uncertainty considerations. Besides, the destructive interventions necessary for the measurements should be kept to a minimum. This paper shows how non‐destructively gathered measurement results can be incorporated into probabilistic reassessments and which effects the implementation of measured data can have when evaluating existing structures, using a prestressed concrete bridge as a case‐study. [ABSTRACT FROM AUTHOR]

Monitoring of the Gerber hinges in the maintenance project Grenzbrücke Basel Monitoring helps to detect damage of structures at an early stage and provides more safety for the users of the infrastructure [1–3]. It is reasonable to consider only neuralgic points to reduce the amount of the measured data and provide clarity. Monitoring can help to receive information about the condition of the structure, the load situation, and environmental influences (e. g. temperature deformations). In the maintenance project, Grenzbrücke Basel, the Gerber hinges are retrofitted by diagonal prestressed rods. Fiber‐optic strain and temperature sensors are applied on the rods to get more information about the stress state. Based on this stress state a warning system is installed. If the stress state exceeds a limit, a message is sent to the responsible engineer. This paper presents the concept of the warning system, the fiber‐optic measurements, and its calibration using trucks with defined loads. [ABSTRACT FROM AUTHOR]

Correction of failure probability of bridges based on experimental load tests Various empirical studies show that the real load‐bearing capacity of road bridges under traffic loads is on average significantly higher than that indicated by deterministic calculation, mainly by the partial factor method for structural design. One cause is, for example, ignoring the contribution of secondary elements to the load‐bearing capacity of the bridge. Since the same static models are often used to calculate the failure probability of bridges as for the deterministic calculations, there must also be an underestimation of the real load‐bearing capacity and thus an overestimation of the failure probability. In this paper different factors to consider these differences for bridges are presented and discussed. [ABSTRACT FROM AUTHOR]

Assessment of strength properties of viaducts made of prestressed concrete – Material investigations on concrete samples from the Lahntal Viaduct near Limburg In 2016 the Lahntal Viaduct was replaced by a new structure. Before the western superstructure was deconstructed, more than 250 cores and other specimens could be taken from the old structure. The present paper deals with the investigations on compressive strength and tensile splitting strength of the concrete. The test results are evaluated statistically and different populations are tested for the taken sample. The goal is to identify a reasonable subdivision of the sample. Furthermore, the design values according to DIN EN 13791 and Eurocode 0 were calculated and compared with calculated expected values. These investigations are intended to provide insights for the assessment of the strength properties of existing viaducts and to develop a safe and economical investigation methodology from them. [ABSTRACT FROM AUTHOR]

Die Straßenbrücke Horsterdamm in Lauenburg kreuzt den Elbe‐Lübeck‐Kanal und die Eisenbahntrasse Lüneburg‐Lübeck. Die alte Straßenbrücke, eine genietete Fachwerkbrücke mit untenliegender Stahlbetonfahrbahn aus dem Jahr 1939, wies erhebliche Schäden auf und musste ersetzt werden. Die neue Brücke wurde als Stabbogenbrücke mit einer Stahlbetonfahrbahn als Verbundkonstruktion geplant und realisiert, wobei zahlreiche Leitungen ein Verschalen auf der Unterseite nahezu unmöglich machten. Zur Realisierung der Fahrbahnplatte wurde daher auf Stahlbetonfertigteile mit Ortbetonergänzung zurückgegriffen. Im Folgenden werden die planerischen und baubetrieblichen Erfahrungen zusammengefasst dargestellt. Abschließend wird auf Vorteile im Hinblick auf Zwangsbeanspruchungen und Erstrissbildung infolge abfließender Hydratationswärmeentwicklung eingegangen. Concrete deck with precast elements and cast in place topping employed at the new road bridge Horsterdamm The new road bridge Horsterdamm in the city of Lauenburg crosses the Elbe‐Lübeck‐Canal and a railway line. The old bridge, a riveted truss bridge, built in 1939, showed severe defects and had to be replaced. The new bridge is designed as an arched bridge with a composite concrete slab. A bunch of pipes and wires under the bridge lead to the decision to employ precast elements with a cast in place topping. The paper deals with some special design aspects and experiences during erection. Special attention is given to the advantages of the precast elements with respect to crack development due to hydration heat and constraint. [ABSTRACT FROM AUTHOR]

Bisher durchgeführte Nachrechnungen bestehender Spannbetonbrücken auf Basis der vom Bundesverkehrsministerium veröffentlichten Nachrechnungsrichtlinie haben in vielen Fällen Defizite der Querkraft‐ und Torsionstragfähigkeit sowie des Ermüdungswiderstands ergeben. In einem Forschungsvorhaben im Auftrag der Bundesanstalt für Straßenwesen wurden daher Bemessungsverfahren formuliert, die in die erste Ergänzung zur bestehenden Nachrechnungsrichtlinie implementiert wurden. Der vorliegende Beitrag beschreibt die entsprechenden Verfahren zur Ermittlung der Querkrafttragfähigkeit unter statischer und zyklischer Belastung ohne Berücksichtigung einer Querkraftbewehrung. Die Verfahren berücksichtigen neben neueren Forschungsergebnissen die technischen Regelwerke für Betonbrücken und basieren auf einem Nachweis der Hauptzugspannungen. Anhand einer typischen Hohlkastenbrücke des Bundesautobahnnetzes werden die Anwendung der Verfahren exemplarisch erläutert und die wesentlichen Ergebnisse dargestellt. Principal tensile stress criterion for the shear assessment of existing concrete bridges The structural assessment of existing road bridges that has been recently performed on the basis of the equally named provisions, issued in 2011 by the Federal Ministry of Transport and Urban Affairs, have revealed significant deficits in shear and torsion as well as fatigue resistance especially in prestressed concrete bridges. In a research project, funded by the Federal Highway Research Institute of Germany, design methods have been developed that were incorporated into the first addendum of the Structural Assessment Provisions. This paper describes the respective design methods for shear under static and cyclic loading without shear reinforcement. The procedures take into account current research results as well as the design codes for concrete bridges and are based on a verification of the principal tensile stresses. The use of the procedure and the main results are shown exemplarily by a design example of a typical box girder bridge of the German road network. [ABSTRACT FROM AUTHOR]

Expansion joints and structural bearings developed on the basis of component testing Expansion joints and structural bearings are especially for bridges, as key elements of our infrastructure, of special importance. Since late 1950s IMB/MPA Karlsruhe assigns a unique role in the development and assessment of these complex construction products. In particular by harmonized European Standards and European Technical Assessments this role has gained further weight and influence. By means of various examples for component testing this paper will demonstrate, how by the support of IMB/MPA Karlsruhe high performance solutions for structural bearings and expansion joints have been developed and regarding the assessment new methods have been elaborated, as well as applied. Whereby it is possible to provide an outlook in the application of future European specifications and allow an insight to newest developments in the field of structural bearings and expansion joints. [ABSTRACT FROM AUTHOR]

Bridges made of prestressed carbon concrete Tendons made of carbon fiber reinforced polymers (CFRP) can be used for the prestressing of concrete bridges. Such tendons can be highly tensioned, they do not rust or fatigue, and they are very lightweight. Their application can lead to more sustainability and elegance in bridge construction, as they allow for slimmer cross‐sections and at the same time increase durability. In this paper, first the status of carbon concrete research at the TU Berlin and the state of the art in bridges with carbon elements is presented. The main focus is then shifted to questions of warning to failure and the cross‐sectional design of components with prestressed and non‐prestressed carbon reinforcement. Finally, the design of a prototype integral frame bridge made at the TU Berlin with precast CFRP posttensioned girders is presented. [ABSTRACT FROM AUTHOR]

In contrast to the Swiss load model used for new bridge structures (SIA 261), which has roots in a Europe‐wide weigh‐in‐motion (WIM) study and considers the full design life of new structures, the model for existing structures (SIA 269) from 2005 is derived from load effects produced by traffic measured by country‐specific WIM observations and considers a reduced return period. With growing concerns regarding the scarcity of resources, efforts should be made to ensure safety by increasing the knowledge of loads and load‐carrying mechanisms, rather than through overdesign. This paper presents the methodology employed to use WIM data for generating maximum expected load effects on bridges and thus give engineers a tool with which bridge load effects can be accurately derived from real traffic. A re‐evaluation using the methodology outlined here began this year. It is planned to use the results of this for the next revision of the Swiss National Annexes to the Eurocodes and SIA 269. [ABSTRACT FROM AUTHOR]

On the consideration of hypothetical numbers of victims in life cycle cost calculations of bridges In the context of risk or life cycle cost assessments of bridges, damage consequences also occur as input parameters in addition to the probability of collapse. One of the most important damage consequences of bridge collapses are possible fatalities. In the context of this paper, known methods for estimating the potential number of fatalities are presented. In the next step, a new method will be developed which makes use of the current state of science regarding bridge collapses. With this method the number of victims can be estimated depending on the type of bridge. [ABSTRACT FROM AUTHOR]

Global challenges in the construction industry regarding the aspect of resource consumption – Resource consumption in global reinforced concrete construction and potentials of carbon concrete composites The construction industry is partly responsible for the increasing consumption of material and energetic resources. It is worldwide dominated by the building material of the century: steel reinforced concrete. The following paper deals with the potential which lies in the use of carbon concrete for a sustainable and resource‐efficient concrete industry. First, the current global and German resource situation in (steel reinforced) concrete construction is presented in numerical terms. The occurrence, availability and consumption of the resources are discussed and an estimate of the annual global concrete consumption is made. Then the energy consumption of individual resources is shown and the resulting global challenges for the construction industry with regard to the importance of sustainable construction methods are analyzed. Finally, the potentials of the C3 construction method (C3: Carbon Concrete Composite) are investigated and put into context on the basis of a material‐related and systemic comparison of steel and carbon concrete. [ABSTRACT FROM AUTHOR]

Correction of collapse probability of bridges The concept of minimizing life cycle costs uses, among other things, the parameter of probability of failure. In contrast to all other parameters, however, a connection with observed collapse frequencies is denied in the literature. In this paper, factors for the correction of the calculated failure probabilities are presented based on the evaluation of collapse statistics. These factors consider e.g. the building material, the type of static system or the type of bridge. This information is usually available in the databases of the infrastructure managers, so that the procedure can be easily integrated into existing databases and at the same time an individual realistic value can be determined for each bridge. [ABSTRACT FROM AUTHOR]

Die CHIO Brücke in Aachen ist eine integrale Fußgängerbrücke mit S‐förmigem Grundriss, die als Schrägkabelbrücke von einem 65 m hohen Pylon abgespannt wird. Die vorliegende Veröffentlichung beschreibt Planung und Bau dieses außergewöhnlichen Tragwerks, das als Entree für das Weltfest des Pferdesports 2014 in Aachen dient. The Chio Bridge in Aachen The Chio‐bridge in Aachen is an integral pedestrian bridge with an S‐shaped floor plan. It is a cable stayed bridge with a 65 m high pylon. This paper describes the design and the building process. [ABSTRACT FROM AUTHOR]

Extremely lightweight bicycle bridge from prestressed carbon‐concrete in Winterthur/Switzerland Very thin concrete slabs reinforced by four or more orthogonal layers of highly prestressed carbon were developed at the Zurich University of Applied Sciences ZHAW in Winterthur. They are produced industrially in three standard thicknesses and in large standard slab sizes. In a separate process they are cut and machined to individual project specifications. The slabs can be used as load carrying elements in very lightweight and sustainable pedestrian bridges. This paper presents the first bridge of this type. Since October 2016 it crosses the river Eulach in Winterthur. With a span of 7.60 m and a clear width of 2.16 m the carbon concrete bridge weighs approximately 3 200 kg. Related to the usable area its weight of 190 kg/m2 corresponds to that of a light steel bridge. A conventional reinforced concrete bridge would have been 4 to 5 times heavier. Due to the innovative, prestressed carbon concrete slabs the resource consumption could be significantly reduced, approximately by a factor of 5. [ABSTRACT FROM AUTHOR]

Im Spannbetonbau kann es aus unterschiedlichen Gründen zu einer zeitlichen Verzögerung zwischen Einbau, Vorspannen und Verpressen von Spanngliedern kommen, was es erforderlich machen kann, eingebaute Spannglieder für eine gewisse Zeit sicher vor einer Korrosion zu schützen. Der Beitrag gibt zunächst einen Überblick über bekannte Untersuchungen und Erfahrungen bei der Anwendung verschiedener temporärer Korrosionsschutzmaßnahmen an Versuchskörpern und Brückenbauwerken. Im Anschluss werden über die Erfahrungen aus einer praktischen Anwendung einer Lufttrocknung bei einem Brückenbauwerk berichtet und der Korrosionszustand der Spannglieder beurteilt. Abschließend werden Empfehlungen abgeleitet, unter welchen Voraussetzungen der temporäre Korrosionsschutz durch eine Trockenluftspülung sicher und zuverlässig gewährleistet werden kann. Temporary corrosion protection – State of the Art and Field Report In prestressed concrete constructions there are different reasons for time delays between manufacturing, prestressing and grouting of prestressing tendons, which can require a temporary corrosion protection of the build‐in and pretensioned tendons for a certain time period. The paper gives an overview of the experimental investigations and experiences in the application of different temporary corrosion protection methods in laboratory test and bridges. Afterwards the experiences of a practical application of a dry air corrosion protection at a bridge construction are presented and the state of corrosion of the tendons is analyzed. Finally recommendations are derived, under which conditions a save and reliable temporary corrosion protection with dry air can be achieved. [ABSTRACT FROM AUTHOR]

Der Untersuchung von vorgespannten Brückenplatten bzw. Fahrbahnplatten kommt angesichts ihrer direkten Belastung durch Verkehr und der Gefahr durch Tausalzeintrag infolge von Schäden an der Abdichtung eine tragende Rolle bei der Planung von Instandsetzungsarbeiten zu. Da diese Bauteile direkt befahren werden, ist der Einsatz zerstörungsfreier Prüfverfahren (ZfPBau‐Verfahren) sinnvoll, wobei deren Anwendung nur einen begrenzten Eingriff in den Verkehr verursachen sollte. In diesem Beitrag werden neben dem großflächigen Einsatz von Radar von der Brückenoberseite aus, d. h. durch den Fahrbahnbelag hindurch, Detailuntersuchungen von der Brückenunterseite mithilfe von Bauwerkscannern beschrieben. Diese Scanner verwenden sowohl Radar als auch Ultraschall mit ihren komplementären Verfahrenseigenschaften, wobei deren Möglichkeiten und Grenzen aufgezeigt werden. Abschließend wird eine Strategie zur Kombination von ZfPBau‐Verfahren sowie deren gezielter großflächiger Einsatz in Abgrenzung zu kleinflächigen Detailuntersuchungen beschrieben. Investigation of prestressed bridgedecks under traffic using non‐destructive‐testing methods The investigations of pre‐stressed bridge decks and carriageway slabs, considering their direct exposure to traffic and threat of ingress of de‐icing salt as a result of damage of the seal, plays a major role in the planning of repair work. Since these building elements are driven directly, the usage of non‐destructive testing (NDT methods) is useful where the application should cause only a limited intervention into traffic. In this paper, in addition to the large‐scale measurements with radar from the outer side of the bridge, which is through the road surface, detailed studies of the bridge base with the help of on‐site scanners are described. These scanners use radar and ultrasonic with their complementary properties. The possibilities and limitations are discussed here. Finally, a strategy for combining NDT methods and their specific large‐scale applications in a distinction to small‐scale detailed studies is described. [ABSTRACT FROM AUTHOR]

Der Beitrag gibt einen Überblick über die in der ehemaligen DDR eingesetzten Spannverfahren und stellt eines davon, das Verfahren ITB, ausführlich vor. Beim Abbruch der Brücke des 10. Jahrestages in Neubrandenburg, bei deren Errichtung dieses Spannverfahren erstmals zum Einsatz kam, wurden Material‐ und Bauteilproben entnommen und diese experimentell untersucht. Mit dem Ziel, das Schubversagen eines Spannbetonbauteils ohne schlaffe Betonstahlbewehrung zu untersuchen, wurde ein aus der Brücke herausgetrennter Träger einem Bruchversuch unterzogen, wobei verschiedene Messverfahren, wie die Photogrammetrie, die Schallemissionsanalyse und die bereichsweise Krümmungsmessung zum Einsatz kamen. Die Ergebnisse dieser experimentellen Untersuchungen werden ausführlich vorgestellt und das Tragverhalten hinsichtlich einer Versagensvorankündigung bewertet. Investigations on a pre‐stressed concrete bridge beam without pre‐tensioned reinforcement The paper gives an overview of the pre‐stressing systems used in the former GDR and describes one system, called ITB, in detail. During the demolition of the bridge “10. Jahrestag” in Neubrandenburg, at which this pre‐stressing system was first used, material samples and a specimen were taken and experimentally investigated. For the objective of the investigation of a pre‐stressed concrete element without non‐pre‐stressed reinforcement, a cut out beam of a bridge was loaded until failure and different measuring technologies, like the photogrammetry, the acoustic emission analyses and the sectionwise curvature‐measurement were used. The results of this experimental investigation are discussed in detail and the bearing behavior according to an unannounced failure is evaluated. [ABSTRACT FROM AUTHOR]

Monitoring of prestressed constructions with Acoustic Emission technique to detect wire breaks Acoustic Emission technique (AE) is successfully used for decades in material research, material testing in laboratory and in structural health monitoring, in machine building industry and plant engineering. Although AE has repeatedly proven its suitability for detecting damage, the method is not yet commonly used in civil engineering outside the laborytory. In Germany, several bridges are monitored permanently with AE to detect damage like prestressing wire breaks or breaks in welding seams [1]. AE to detect wire breaks is recommended for prestressed buildings with risk of stress crack corrosion, other crack risks or for buildings which cannot be inspected according the required standards. In this paper, examples for AE monitoring to detect wire breaks on bridges are shown. Furthermore, tests with the rebound hammer and wire breaks induced by cutting were executed and analysed. To confirm the test results and to provide better visualization and understanding of underlying wave phenomena, two numeric simulations of the sound wave propagation have been conducted. [ABSTRACT FROM AUTHOR]

Shear capacity of carbon reinforced concrete slab bridges with c‐shaped shear reinforcement – Theoretical and experimental investigations for two road bridges in Gaggenau In contrast to design for bending, both engineers and researchers are still confronted with fundamental questions regarding shear design of carbon reinforced concrete. While numerous applications for slabs and thin façade panels without shear reinforcement, some with first general approvals, already exist, there is still a need for research into the technical and economic application of components with shear reinforcement made of non‐metallic textiles. For the construction of two road bridges made of carbon concrete with c‐shaped shear reinforcement, static and cyclic tests were carried out at the Institute of Structural Concrete at RWTH Aachen University. The results show surprisingly low scatter and an excellent fatigue behavior. Overall, there are clear parallels to the shear failure of reinforced concrete or concrete with Fiber‐Reinforced Polymer (FRP) rebars. This paper highlights the application potential and further challenges for the use of carbon concrete apart from filigree individual applications and mere objects of art. [ABSTRACT FROM AUTHOR]

Overpass bridge of the L 3378 road near Fulda‐Lehnerz. First application of UHPC in road bridge construction in Germany. Part 2 In the course of the federal highway B27 UHPC was used for the first time in cast‐in‐situ bridge construction in Germany. Presently, UHPC is not covered by any German standard. Therefore, an approval for this individual application case was necessary. The bridge superstructure has been designed as 4‐web T‐beam construction made of prestressed concrete with a top layer made of in‐situ normal strength concrete and UHPC, respectively. Because of UHPC's high impermeability against liquids, the cost and timely intensive application on a waterproofing was waived. Besides its strengthening abilities the applied UHPC layer with a thickness of 70 mm is intended to effect as a sealing. Additionally to its average compressive strength of > 150 MPa the applied UHPC has been specifically developed to enable a bridge inclination of 3.5 %. In total, 57 m3 of UHPC was produced in a concrete plant and transported and cast on site. By this pilot project, the successful practicability of using UHPC as strengthening and waterproofing measure in bridge construction in Germany could be demonstrated. The following paper particularly deals with aspects of concrete technology and quality control for the UHPC used. [ABSTRACT FROM AUTHOR]

Overpass bridge of the L3378 road near Fulda‐Lehnerz. First application of UHPFRC in road bridge construction in Germany. Part 1 Aging bridges of the German federal road network often cannot be rehabilitated or replaced timely due to insufficient funding and complex regulations of building laws. Consequently, novel building materials and alternative solutions get the opportunity to demonstrate their performance. The novel building material UHPFRC was recently used for targeted rehabilitation and strengthening of structures in reinforced concrete leading to increase of service duration. The replacement of the overpass over the federal highway B 27 near Fulda gave the opportunity to cast, under construction site conditions, a layer of UHPFRC on top of the slab for both protective waterproofing and structural resistance functions. This paper reports on the project development, design, tendering and the construction. [ABSTRACT FROM AUTHOR]

Der vorliegende Beitrag befasst sich mit der Instandsetzung, Verstärkung und Verbreiterung der 'Nels River Bridge' in der Provinz Mpumalanga in Südafrika. Es werden die Komplexität der einzelnen Bemessungsschritte dargestellt und Lösungen und Konstruktionstechniken erörtert, die angewendet wurden, um das Projekt erfolgreich zum Abschluss zu bringen. Repair and Widening of the Nels River Bridge on Road R37 in South Africa This paper deals with the repair, strengthening, improvement and widening of the Nels River Bridge situated in the Mpumalanga province of South Africa. The paper outlines the design complexities and discusses the solutions and the construction techniques followed that resulted in a successful project. [ABSTRACT FROM AUTHOR]

Comparison of probability of failure and collapse frequency of bridges This paper compares the collapse frequency of bridges with the goal values of the probability of failure according to modern codes of practice. The estimation of the collapse frequency is based on the review of existing publications related to different regions and different times in terms of a meta-analysis. Furthermore goal values of the probability of failure for new and existing structures are discussed in short. The comparison reveals a good agreement between the goal values and the observed values. [ABSTRACT FROM AUTHOR]

Experimental validation of a railway bridge made of a reinforced UHPFRC-Tbeam The material UHPFRC is not yet used in the field of bridge construction regularly. The reasons are missing codes and allurements for innovation in the structural engineering. Nevertheless, UHPFRC has many advantages, which are significant compared to the use of concrete in this case: the replacement of a railway bridge. This paper documents two tests of reinforced UHPFRC beams. This tests has been done in the context of the validation of the dimensioning: one bending test and one shear forcer test. Furthermore, the reasons for the choice, the specimen geometry as well as the test results are presented. Finally, the investigated load bearing capacities will be compared with analytical models. [ABSTRACT FROM AUTHOR]

Structural monitoring for safeguarding the remaining life time of a bridge building endangered by stress corrosion cracking Initial point of the structural monitoring of the bridge over the railway in Waren (Müritz) were the results of recalculation and the investigations of the prestressed wires. In this regard it was documented, that the bridge is in fact endangered by stress corrosion cracking, but ductility provides a sufficient prior notice of failure. Thus the further use of the bridge is possible, provided of a shortened inspection interval. Due to ongoing use the inspection of the building is possible to a limited extend only, the necessary frequent visual assessment was replaced by a structural monitoring. So the focus was not on the complete measurement based observation of the building. The main aim of the structural monitoring rather was the purposeful and economical registration of possibly developing bending cracks. During the monitoring period of two years the development of a bending crack under service load was detected and thereby the real arise of the crack-before-failure-criterion was confirmed. The paper shows the principle procedure of collecting information as basis for a safe decision making as well as on planning, execution and evaluation of structural measurements and their integration into the assessment process of the structure. [ABSTRACT FROM AUTHOR]

Computation of temperature fields on bridges - Implemen tation by means of spread-sheets Non-uniform heating causes internal stresses in statically indeterminate systems. In bridge calculation and design, these are usually considered by linear temperature gradients. Beside these linear vertical gradients, the average temperature of the cross-section is relevant for structural design. In return, nowadays standards provide deterministic values or simplified distributions for recalculation which are based on investigations of typical structures seen as representative for the entire stock. Thus, characteristics derived therefrom do not cover local features that might be beneficial like regional ambient conditions, partial clouding or a structure's specific orientation. Actually, general temperature characteristics from codes can be substituted with local information if the temperature distribution and its key parameters are extracted from the local time-variable temperature field directly. The paper shows how transient, non-stationary temperature fields can be computed from long-term climate data by means of spread-sheet analysis. For this purpose, Fourier's differential equation of heat transfer is solved with finite elements employing boundary conditions, which reflect the ambient climate conditions. Key features of the methodology are discussed in detail, while the obtained results are strictly compared to measurement data from a temperature-monitoring of a pre-stressed concrete bridge. Computed results comply well with these measurements. [ABSTRACT FROM AUTHOR]

Mit der Einführung der Richtlinie zur Nachrechnung von Straßenbrücken im Bestand wird den Planern und Ingenieuren ein Werkzeug in die Hand gegeben, das durch spezielle Regelungen und Vorgaben die Möglichkeit bietet, bestehende Straßenbrücken realistisch zu bewerten. Die Nachweisführung kann dabei in vier Stufen erfolgen, wobei insbesondere die 4. Stufe wissenschaftliche, d.h. auch probabilistische Methoden für die Nachrechnung der bestehenden Straßenbrücken vorsieht. Die Forschung auf dem Gebiet der Probabilistik wurde in den letzten Jahrzehnten stark vorangetrieben, sodass nunmehr Modelle und Rechenmethoden zur Verfügung stehen, die einen Einsatz dieser Methoden in der Baupraxis ermöglichen. Im Beitrag wird ein mögliches praktisches Vorgehen für die Durchführung probabilistischer Berechnungen als zusätzlicher Baustein bei der Bewertung bestehender Brückenbauwerke aufgezeigt. Der Sensitivitätsanalyse, die im Rahmen einer solchen Berechnung stets durchgeführt wird, kommt dabei besondere Bedeutung zu, da dadurch die für die Zuverlässigkeit des Bauwerks maßgebenden Einflussgrößen genau identifiziert werden können. Zudem werden im Beitrag Hinweise für die stochastische Modellierung von Einwirkungen, Widerständen und Modellunsicherheiten bei der praktischen Anwendung gegeben. An zwei konkreten Beispielen werden exemplarisch die wesentlichen Schritte erläutert und die Vorteile des Verfahrens verdeutlicht. Probabilistic analysis methods as an additional component for the integrated assessment of existing bridges With the implementation of the guideline for the assessment of existing bridges (Nachrechnungsrichtlinie) a tool is given to designers and engineers, which offers the possibility of a realistic assessment of existing bridges by special arrangements and requirements. The analysis can be done in 4 steps. In step 3 and particularly in step 4 it is allowed to use scientific, e. g. probabilistic methods, for the assessment. The research in the field of probabilistic analysis was strongly promoted in recent decades. The tools for modelling and computing are now available which allows the use of probabilistic methods in the engineering practice. The paper shows a possible procedure for the probabilistic assessment of existing structures. The sensitivity analysis is here of special importance. This analysis shows the impact of each influencing parameter of loads and resistance on the reliability of the bridge. In addition to the presentation of the approach the paper gives details for the stochastic modelling of loads, resistance and model uncertainties. Two examples, a prestressed concrete girder bridge and a reinforced concrete arch bridge, show the advantages of the presented approach. [ABSTRACT FROM AUTHOR]

The M4 Elevated Section in West London is a 1.9 km concrete viaduct structure providing a major arterial route into London. An intervention model bringing together structural assessment and forecast deterioration, corrosion modeling and cracking has been developed to prioritise structural rehabilitation of the substructure crosshead beams. To evaluate residual strength an initial assessment of crossheads was undertaken, which identified a deficiency in tensile capacity at the ends of the crosshead cantilevers compared to current demands. Further assessment has been undertaken, including three dimensional strut and tie, non-linear finite element analysis and plastic analysis, to confirm public safety with continued trafficking of the structure, and to determine the need for strengthening. Additionally extensive monitoring of the crossheads has been implemented including mapping of all cracks, and remote crack monitoring to safeguard the substructures and allow early interventions. The long term maintenance strategy brings together strengthening and cathodic protection concrete preservation methods with removal and repair of concrete delamination. This paper discusses the development of the prioritisation process including deterioration modeling, together with the extended structural analysis to formulate a strengthening programme for these substructures. [ABSTRACT FROM AUTHOR]

A change in the ship traffic volume is expected as a result of upgrading of many European waterways. There is a correlation between an improved waterway passage, an increased ship size and higher frequency of larger ships. On the one hand, the ecological and economic advantages of the upgrading process cannot be disputed, but on the other hand, the changed shipping traffic results in additional risks, especially to bridge substructures. Most of the current bridges were built more than 30 years ago and were generally not dimensioned for horizontal forces expected from a ship impact according to modern codes. This paper provides some information on theoretical background of ship impact analysis and challenges associated with numerical modelling. In particular, it also provides two case studies of historical bridges over river Main. A detailed discussion of provided structural solution is provided along with recommendations. [ABSTRACT FROM AUTHOR]

Bei dem Hochstraßenabschnitt der M4 in West London handelt es sich um einen Betonbrückenbau von 1,9 Kilometer Länge, der eine Hauptverkehrsachse für die Zufahrt nach London darstellt. Um die Instandsetzung der Brückenquerträger dem Grad der Schädigung nach zu priorisieren, wurde ein Maßnahmenmodell ausgearbeitet, das die Bewertung der Tragsicherheit mit der prognostizierten Zustandsverschlechterung, der Modellierung der Korrosion und der Rissbildung verknüpft. Um die öffentliche Sicherheit bei einer fortdauernden Verkehrsbelastung sicherzustellen sowie den Verstärkungsbedarf zu ermitteln, wurden weitere Bewertungen durchgeführt; darunter eine dreidimensionale Fachwerkmodellanalyse, eine nichtlineare Finite-Elemente-Analyse und eine plastische Analyse. Management of the M4 Elevated Section Substructures The M4 Elevated Section in West London is a 1.9 km concrete viaduct structure providing a major arterial route into London. An intervention model bringing together structural assessment and forecast deterioration, corrosion modeling and cracking has been developed to prioritise structural rehabilitation of the substructure crosshead beams. To evaluate residual strength an initial assessment of crossheads was undertaken, which identified a deficiency in tensile capacity at the ends of the crosshead cantilevers compared to current demands. Further assessment has been undertaken, including three dimensional strut and tie, non-linear finite element analysis and plastic analysis, to confirm public safety with continued trafficking of the structure, and to determine the need for strengthening. Additionally extensive monitoring of the crossheads has been implemented including mapping of all cracks, and remote crack monitoring to safeguard the substructures and allow early interventions. The long term maintenance strategy brings together strengthening and cathodic protection concrete preservation methods with removal and repair of concrete delamination. This paper discusses the development of the prioritisation process including deterioration modeling, together with the extended structural analysis to formulate a strengthening programme for these substructures. [ABSTRACT FROM AUTHOR]

Zur Vereinheitlichung der Vorgehensweise bei der Nachrechnung von Straßenbrücken wurde in Deutschland im Mai 2011 die 'Nachrechnungsrichtlinie' eingeführt. Im Rahmen eines von der deutschen Bundesanstalt für Straßenwesen (BASt) initiierten und von den Autoren des vorliegenden Beitrags bearbeiteten Forschungsvorhabens wurden in den vergangenen Monaten Nachrechnungsergebnisse zu insgesamt 146 Betonbrücken aus ganz Deutschland gesammelt und ausgewertet. Wesentliches Ziel des Projekts war es, Grundlagen für eine noch effizientere Nachrechnung mit aussagekräftigen Ergebnissen zu schaffen. Nachfolgend werden zunächst typische 'rechnerische Defizite' benannt, welche Zusatzbetrachtungen erforderlich machen, die über die Anwendung der Sonderregelungen der Nachweisstufe 2 hinausgehen. Anschließend werden Empfehlungen zur Nachrechnung allgemein sowie zum Umgang mit rechnerischen Defiziten gegeben und es werden Vorschläge zur Aufbereitung von Nachrechnungsergebnissen vorgestellt und diskutiert. Findings and insights concerning the results of re-analyzed concrete bridges in Germany In May 2011 the new guideline 'Nachrechnungsrichtlinie' (standard for bridge re-analysis and assessment) was recommended for application in order to implement a harmonized basis for the assessment of existing road bridges. Within the framework of a research project initiated and funded by the Federal Highway Research Institute (BASt) re-analysis results of in total 146 concrete bridges were collected and evaluated. One major goal of this project was to provide a basis for a more efficient re-analysis and an improved documentation of the results. The present paper firstly describes typical 'calculatory deficits' requiring additional considerations upon completion of the so-called re-analysis stage 2. Subsequently, general recommendations for future re-analyses are being provided, advices are given in terms of the handling of deficits and a proposal is made and discussed regarding presentation and documentation of re-analysis results. [ABSTRACT FROM AUTHOR]

Im Zuge des kontinuierlichen Ausbaus der norwegischen Infrastruktur erfolgt seit September 2010 die endgültige Fertigstellung der Dalsfjordverbindung an der Westküste Norwegens. Neben etwa 3, 8 Kilometer Tunnelkonstruktion ist der Bau der Dalsfjord-Hängebrücke der bedeutungsvollste Bestandteil dieser Neubaumaßnahme. In diesem Beitrag werden die wesentlichen Betonarbeiten der Hängebrücke erläutert. Diese umfassen die Tragseilverankerungen, die Pylone sowie die Vorlandbrücken. Neben der Darstellung von Ausführungsthemen wird auf die projektspezifischen Besonderheiten eingegangen. Speziell Wetter, Strömungen und (in den Wintermonaten) wenig Sonnenlicht sowie die begrenzte Verfügbarkeit von Baustoffen und Maschinen erforderten eine detaillierte Arbeitsvorbereitung. Zudem erschwerten begrenzte Zugangsmöglichkeiten und geringe Ausweichflächen die Ausführung. Dalsfjordbrua - 523 meters suspension bridge in western Norway As part of the continuous expansion of the Norwegian infrastructure since September 2010, the final completion of the Dalsfjord connection has started on the west coast of Norway. In addition to approximately 3.8 kilometer of tunnel construction, building the Dalsfjord suspension bridge is the most significant part of this new connection. In this paper, the essential works of the concrete suspension bridge are explained. These include the cable anchorages, the pylons and the approach bridges. Besides the representation of construction details, in particular project-specific features are presented. Especially weather, currents and limited sunlight (during winter months) as well as the limited availability of building materials and machinery required a detailed work preparation. In addition limited access and little alternative areas had made execution difficult. [ABSTRACT FROM AUTHOR]

Im Mai 2011 hat das Bundesministerium für Verkehr, Bau und Stadtentwicklung (BMVBS) die 'Richtlinie für die Nachrechnung von Straßenbrücken im Bestand' (Nachrechnungsrichtlinie) bekannt gegeben. Unmittelbar darauf wurden in Bayern im Rahmen einer Pilotprojektphase verschiedene Straßenbrücken unter Zugrundelegung dieser Richtlinie nachgerechnet - darunter auch die Donaubrücke bei Ingolstadt im Zuge der BAB A9. Bei der Nachrechnung dieser 1976 errichteten Spannbetonbrücke mit Hohlkastenquerschnitt zeigten sich nach Stufe 1 und auch noch nach Stufe 2 der Nachrechnungsrichtlinie erhebliche rechnerische Defizite vor allem im Bereich des Anschlusses der Druckgurte in den Stützbereichen an die Stege. Durch die kombinierte Anwendung von physikalisch nichtlinearen Rechenverfahren und ergänzenden Bauwerksuntersuchungen konnten in Stufe 4 der Nachrechnungsrichtlinie letztlich alle Nachweise ohne Einschränkungen erbracht und daher auf verkehrsbeschränkende oder Verstärkungsmaßnahmen verzichtet werden. Im Rahmen des Beitrags werden die Vorgehensweise und die wesentlichen Ergebnisse der durchgeführten Berechnungen zusammengefasst. Abschließend werden die an der Donaubrücke Ingolstadt gewonnenen Erkenntnisse mit Ergebnissen eines aktuellen Forschungsvorhabens verglichen, das sich mit der systematischen Analyse von bisher durchgeführten Nachrechnungen von Massivbrücken befasst. Assessment and re-analysis of the BAB A9 Danube bridge Ingolstadt In May 2011 the new guideline 'Nachrechnungsrichtlinie' (standard for bridge re-analysis and assessment) was recommended for application by the Federal Ministry of Transport, Building and Urban Development. Since then several pilot projects have been launched in Bavaria aiming on the re-analysis of different types of major road bridges based on the assessment guideline. One of these bridges is the BAB A9 Danube PC box girder bridge next to Ingolstadt. Upon completion of the re-analyses according to the so-called levels 1 and 2 of the guideline there were still severe calculatory deficits particularly regarding the connection zones of the compression flanges and webs close to the supports. By using a 3D FE model and physically non-linear analysis methods combined with in-situ investigations (i.e. level 4 of the guideline) it was finally possible to fulfill all design criteria and hence to avoid both traffic restrictions as well as strengthening measures. The present paper describes the general assessment approach and highlights important findings and results of the non-linear analyses. Finally, the Danube Bridge results are discussed with the background of a current research project focusing on a systematic evaluation of available re-analyses of RC/PC bridges performed on the basis of the new assessment guideline. [ABSTRACT FROM AUTHOR]

Brücken aus den 1960-70er-Jahren wurden aufgrund der hohen Vorspannung häufig mit sehr geringen Querkraftbewehrungsgraden ausgeführt. Weist man die betroffenen Brücken nach DIN-Fachbericht 102 mit den neuen Lastmodellen aus DIN-Fachbericht 101 nach, ergibt sich in vielen Fällen eine deutlich höhere erforderliche Querkraftbewehrung als in den Stegen vorhanden. Zur Untersuchung der Ermüdungsfestigkeit von Spannbetonträgern mit Querkraftbewehrung wurden Ermüdungsversuche an 14 Trägern mit geringem Querkraftbewehrungsgrad ( ρ w = 0,15%, ρ w = 0,22% und ρ w = 0,33%) durchgeführt. Der Beitrag beschreibt die experimentellen Untersuchungen und das in den Versuchen beobachtete sukzessive Versagen der Querkraftbewehrung unter zyklischer Beanspruchung. Anhand von Vergleichsrechnungen und den im Versuch ermittelten Druckstrebenwinkeln wurde ein Ansatz zur Ermittlung der Spannungsschwingbreite der Querkraftbewehrung unter zyklischer Belastung entwickelt. Der Ansatz basiert auf dem Fachwerkmodell mit variablem Druckstrebenwinkel. Fatigue of prestressed beams with web reinforcement under cyclic shear Many existing bridge structures built in the 1960s and 1970s typically feature a high degree of prestressing and low shear reinforcement ratios. Therefore, their shear bearing capacity, originally determined based on the principal tensile strength criterion, can often not be verified with the strut and tie models of DIN-Fachbericht 102. To investigate the shear strength of prestressed concrete beams with web reinforcement under cyclic loading, fatigue tests on 14 beams with a low amount of shear reinforcement ( ρ w = 0,15%, ρ w = 0,22% and ρ w = 0,33%) were performed. The present paper describes the fatigue tests and the occurring gradually stirrup fractures with increasing number of load cycles. Based on comparative calculations and the experimentally determined strut inclinations, a modified approach to calculate the stirrup stress amplitude under cyclic loading has been developed. It is based on a truss model with variable strut inclination. [ABSTRACT FROM AUTHOR]

Die Anforderungen an Brückenbauwerke haben sich in den vergangenen Jahren infolge der steigenden Verkehrszahlen deutlich erhöht. Gleichzeitig hat sich mit der Umstellung der Normen der rechnerische Querkraftwiderstand von Bauteilen ohne Querkraftbewehrung verringert. Als Folge lässt sich für Brückenbauwerke im Bestand mit Fahrbahnplatten ohne Querkraftbewehrung nach derzeitigen technischen Regeln oft keine ausreichende Querkrafttragfähigkeit nachweisen. Daher wurde im Rahmen eines von der Bundesanstalt für Straßenwesen (BASt) geförderten Forschungsvorhabens das Querkrafttragverhalten von Fahrbahnplatten aus Stahlbeton genauer analysiert. Der vorliegende Aufsatz beschreibt die Ergebnisse der experimentellen Untersuchungen zur maßgebenden Lastverteilungsbreite für Radlasten bei einfeldrigen, gelenkig gelagerten Platten ohne Querkraftbewehrung. Experimental investigations on the effective width for shear of single span bridge deck slabs The requirements for the load-carrying capacity of bridges have increased significantly due to rising traffic loads in the last decades. Furthermore, the design rules of the German codes have changed leading to smaller calculated shear capacities of reinforced concrete members without shear reinforcement. Therefore, the calculated shear capacity of a large number of existing concrete bridge deck slabs without shear reinforcement is not sufficient. For the above reasons, the shear-bearing behaviour of slabs has been investigated within a research programme funded by the Federal Highway Research Institute of Germany (BASt). The paper presents the results of the experimental investigations on the effective width for shear of simply supported single span slabs without shear reinforcement. [ABSTRACT FROM AUTHOR]

Brücken aus den 1960-70er Jahren wurden aufgrund der hohen Vorspannung häufig mit sehr geringen Querkraftbewehrungsgraden ausgeführt, die kleiner als die heute üblichen Mindestquerkraftbewehrungsgrade sind. Ursprünglich nach dem Hauptzugspannungskriterium bemessen, lassen sich diese Brücken heute nicht mit den Fachwerkmodellen nach DIN-Fachbericht 102 nachweisen. In der vorliegenden Untersuchung wird der Querkraftnachweis nach dem Hauptzugspannungskriterium (Gl. 4.119 DIN-Fachbericht 102) für zyklische Beanspruchung (Ermüdung) erweitert. Der Beitrag beschreibt die durchgeführten Ermüdungsversuche an sechs Trägern ohne Querkraftbewehrung mit einem doppeltsymmetrischen profilierten I-Querschnitt und sieben Trägern mit einem Plattenbalkenquerschnitt. Anhand der ertragenen Lastspiele wurden für Spannbetonträger ohne Querkraftbewehrung modifizierte Hauptzugspannungskriterien in Form von GOODMAN-Diagrammen zur Ermittlung der Querkrafttragfähigkeit unter zyklischer Beanspruchung entwickelt. Fatigue of prestressed beams without web reinforcement under cyclic shear Many existing bridge structures built in the 1960s and 1970s typically feature a high degree of prestressing. They often contain less web reinforcement than the actually required minimum web reinforcement. Therefore, their shear bearing capacity, originally determined based on the principal tensile strength criterion, cannot be verified with the strut and tie models of DIN-Fachbericht 102. Within a research programme, the shear design based on the principal tensile strength criterion has been modified for cyclic shear load (shear fatigue). The present paper describes the performed fatigue tests on six I-shaped and seven T-shaped prestressed beams without web reinforcement. Based on the resisted load cycles until failure, modified approaches for shear fatigue in terms of GOODMAN-Diagrams based on the principal tensile strength criterion have been developed. [ABSTRACT FROM AUTHOR]