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Translation abstract Deformation monitoring of bridges applying remote sensing satellite radar measurementsDeformations of the Earth's surface can be measured from space using remote sensing radar interferometry (InSAR). This paper demonstrates the use of these data for deformation monitoring on the Schottwienbrücke‐S6 Semmering motorway. The European Space Agency (ESA) recently began providing free research satellite data from the Sentinel‐1 mission. The approach uses historically recorded natural reflection points as well as corner reflectors artificially attached to the structure. These are measured coordinately and analyzed using remote sensing methods. Thermal displacements of the structure are compensated to increase accuracy. A new model predicts the temperature of the structure based on network weather data. This means that the deformation measurements from the satellites can be analyzed and thermally compensated without sensors on the building, and the deviations can be more than halved. The recorded and processed annual measurements from 2022 onwards show a standard deviation of 1.7 to 3.0 mm compared to the reference system (Liquid Leveling System). Good agreement with the long‐term settlement behavior of the bridge was also found for natural reflection points. Satellites can also be used to simultaneously record different structures at 6‐day intervals up to 2016. Due to the time‐delayed processing, they are currently well suited for long‐term deformation monitoring of long‐span bridges. [ABSTRACT FROM AUTHOR]

Distributed crack width measurement in concrete structures using fibre‐optic sensor technology – New application of distributed fibre optic sensing Cracks and their changes are important indicators for concrete structures. Conventional crack sensors can only detect known cracks or determine their change in width. This paper presents a new crack measurement system that uses low‐cost fibre optic sensors subsequently bonded to the concrete surface to detect cracks over long distances without knowing their location in advance. With distributed fibre optic sensing (DFOS), new cracks can be identified using fibre length of up to 70.0 m. The position of identified cracks can be located to 3.5 cm and their change in width determined. The achieved accuracies for the width are 0.035 mm (laboratory scale) and 0.15 mm (real applications). With DFOS, individual cracks can be measured at the usual crack distances of 15 cm in reinforced concrete construction, even without a possibility of visual inspection. Furthermore, a newly developed evaluation algorithm is presented with which the historical crack development is recorded. In the case of epoch measurements, this can be used to draw conclusions about the maximum crack width that has occurred in the meantime. Laboratory tests and real measurements in the course of a pilot application of more than one year show the methodology as well as the boundary conditions for the choice of fibre and adhesive. Comparisons of different measuring systems show an achieved accuracy in a similar order of magnitude as conventional crack sensors. [ABSTRACT FROM AUTHOR]

Measurement data based load analysis of precast concrete pavements of motorways In Austria, about 40 % and in Germany about 30 % of the motorway and expressway network are concrete pavements. However, very little is known about the stress conditions and temperature loads actually acting in concrete pavements. There is little in‐situ data available, mainly because of the difficulties involved in measuring these conditions in a real paving environment. In the course of a research project, precast slabs were used for the first time to repair concrete pavements in a highway in Austria, and these were also extensively equipped with embedded fiber optic sensors. In an in‐depth analysis of the measurement data of a period of two years, temperature changes, extremes as well as gradients in connection with external weather conditions are evaluated. With regard to the formation of cracks and constraints in the slab, on the one hand measured strains without traffic load are analyzed, on the other hand a statistical analysis of the measured impacting traffic load changes is carried out. In the second section, based on a calibrated nonlinear FE model, a combined analysis of the unsteady stress profile of the slab under dynamic traffic loading with varying temperature‐mechanical loading is performed. After comparison with measured data, the dynamic stress maxima acting in the plate can be determined. [ABSTRACT FROM AUTHOR]

Estimating traffic‐induced vibrations of road bridges prior to concreting works – Creating a meta‐model for preliminary estimation of the risk of early‐age concrete being negatively affected during its hardening by ongoing traffic The interaction between the bridge and the vehicles passing over it is governed by very complex interrelationships, effects of which are difficult to predict. When construction works on existing concrete bridges take place, vibrations caused by ongoing traffic pose a potential risk for the early‐age concrete, which may be being negatively affected during its hardening process. But especially in the course of the planning of construction processes and procedures, a preliminary estimate of potential risk would be helpful. For this reason, large‐scale computation series based on calculation models of entire bridge populations was executed. The aim was to estimate the traffic‐induced vibrations of slab and T‐beam bridges in common configurations to be able to take appropriate steps in planning of construction works and protect the young concrete in its critical hardening phase. The bridge vibrations were calculated by transient FE‐simulation for a large number of truck passages, while bridge properties such as span, slenderness, etc. on one hand, and crossing parameters such as road surface and driving speed and lane on the other hand, were varied. The consideration of individual parameters turned out to be insufficient, therefore a meta‐model in the form of simple equations was formed based on the large data set created. The meta‐model combines the influence of several parameters and provides an initial estimate of the expected vibration amplitudes, which supports decision‐making in the planning of necessary measures. [ABSTRACT FROM AUTHOR]

Test Set‐Ups on corrosion damaged cantilever walls – research project SIBS Retaining walls such as other structures are subjected to ageing or other environmental influences. Concrete structures, and especially RC‐structures, suffer from concrete spalling, cracking or corrosion. Given by slender cross sections and high degrees of reinforcement (e. g. cantilever walls) corrosion damages can influence the bearing capacity and the stability. Especially the earth‐sided regions of such structures (position of the bending reinforcement) and the connection areas between the vertical wall and the foundation slab can be subjected to such damage. In these areas, a non‐uniform and wide‐ranging corrosion pattern can be found, which is not visible during an inspection. This report gives a short overview on (corrosion related) damages and there causes, as well as a short insight in testing methods used for the safety assessment. Furthermore, a monitoring concept for corrosion damaged RC‐structures is presented. The installation and the validation of this concept is shown on a series of mock‐ups and the results are compared with numerical parameter studies. [ABSTRACT FROM AUTHOR]

Traffic vibrations during concreting work on existing road bridges – Vibration prognosis for the assessment of construction stages in course of the newly constructed highway bridge A 23 – Hochstraße Inzersdorf The construction works on existing bridges must often take place without traffic interruptions. During bridge‐widening works or closing of construction joints, the hardening concrete is exposed to traffic‐induced vibrations. This can damage the material permanently, depending on the amplitude of vibration velocity. This study investigates factors that influence amplitude of traffic‐induced vibrations of a slab bridge on the A 23 motorway in Vienna, which was rebuilt in several construction phases. Transient dynamic simulations were used to analyze the influence of the driving speed, vehicle mass and road evenness. Measured road profile data, which were collected by high‐resolution laser scanning of the road surface, were used in FEM simulations. Bridge resonance properties were verified by vibration measurements. While bridge deflections and strains are mainly influenced by vehicle mass, the vibration velocities are primarily determined by the road profile. The predicted vibration velocities were compared to a limit value taken from the literature, the observance of which should not lead to any impairment of the young concrete. The results served as a decision basis for the selection of suitable measures during the critical hardening phase of the concrete in the connection joint. [ABSTRACT FROM AUTHOR]

Effects of traffic‐induced vibrations on young concrete: part 1 In the COUNT (Concreting under traffic) research project, the effects of traffic vibrations on young concrete are extensively examined. This research question has recently become more relevant since traffic closures often have to be imposed when bridges are renovated or widened, as there is a concern that the vibrations caused by traffic will damage the young (hardening) concrete. COUNT aims to determine critical vibration values and underlying damage mechanisms based on three test series. Both harmonic and real bridge vibrations due to train, truck and car traffic are adopted, and the effects on the material concrete itself are investigated, as well as on the bond behaviour between concrete and reinforcement, and the contact between existing and new concrete parts. This first part of the article reports on the results of test series 1 and 2, in which small samples were systematically excited by artificial vibrations during hardening. It was found that conventional traffic vibrations do not affect the strength of concrete per se, but that the bond between the concrete and the reinforcement can be weakened if the vibrations are too great. In addition, it was found that (differential) displacements is a more suitable measure for damage assessment than the vibration velocity. [ABSTRACT FROM AUTHOR]

Over the last years, an increase of damages and defects of geotechnical structures has been observed during detailed safety assessments. This is mostly related to the rising age of these structures and the related decrease of the bearing capacity. The handling and dealing with these existing structures will be a challenging task for future civil engineers. This article should give an insight into damages and defects of retaining structures, which are quite difficult to detect and evaluate in terms of safety and risk. The first part of the article gives a short overview on the state of the art when it comes to the safety assessment of existing retaining structures and introduces a new, currently being edited, ÖGG guideline for this field of civil engineering. The second part deals with corrosion-induced damages on cantilever walls and shows first results of the research project SIBS (safety assessment of existing retaining structures). [ABSTRACT FROM AUTHOR]

Tragwerksverstärkungen sind häufiger erforderlich, damit werden effiziente Verstärkungsmethoden immer wichtiger. Schlaff auf die Betonoberfläche aufgeklebte kohlefaserverstärkte Lamellen (CFK) sind mittlerweile in der Bauwirtschaft etabliert. Dieser Beitrag behandelt das Verfahren von in Betonschlitze geklebten und vorgespannten CFK-Lamellen (engl. Prestressed Near Surface Mounted, kurz: PNSM). Diese neue Technologie ermöglicht es, eingeschlitzte CFK-Lamellen nicht nur im schlaffen, sondern auch im vorgespannten Zustand zu verwenden, wodurch die mechanischen Eigenschaften von CFK-Lamellen optimal genutzt werden können. Darüber hinaus kann durch Aktivierung des Eigengewichtes und durch ein verbessertes Verformungs- und Rissverhalten verstärkter Bauteile die Praxistauglichkeit wesentlich gesteigert werden. Früher war der Spannvorgang sehr aufwendig und es wurden teure Verankerungen am Bauwerk belassen. Diese mussten zudem über die gesamte Nutzungsdauer zuverlässig vor Korrosion geschützt werden. Mit der Composite Wedge-Technik wurde eine temporäre Spannvorrichtung entwickelt, die die Vorspannkräfte innerhalb der Betondeckung durch Keiltechnik rasch und einfach aufbringt. Für den Endzustand wird die Verstärkungsmaßnahme mit einer Klebeendverankerung aus einer Epoxidharz-Quarzmischung dauerhaft abgeschlossen. So werden keine korrosionsgefährdeten Komponenten ins Bauwerk eingebracht und Kostenvorteile geschaffen, da die für den Spannvorgang temporär eingesetzten Keile wiedergewonnen werden. Die Vorspannvorrichtung und Verstärkungsmethode mit Klebeendverankerung wurden im Rahmen des Forschungsprojekts 'Tragwerksverstärkungen mit vorgespannten eingeschlitzen CFK-Lamellen' an der TU Wien entwickelt und im Rahmen von zahlreichen Versuchen getestet. Efficient Prestressing of FRP-Strips Strengthening of structures is an emerging engineering field, and requires an efficient strengthening method. Strengthening with pre-stressed near surface mounted (PNSM) carbon fibre reinforced polymers (CFRP) is a powerful technique, where CFRP-strips are placed and pre-stressed in a groove within the concrete cover. The utilisation of CFRP can be increased and the advantages of PNSM are as follows: the activation of dead loads, a better performance for deflection as well as cracks, an improved bond behaviour and protection of the strip against impacts. On the other hand the pre-stressing action is very elaborate, and often very expensive anchorages have to remain at the structure, which have to be protected against corrosion. By using the Composite Wedge-Technique a pre-stressing unit for the PNSM-Method was developed, which operates within the concrete cover and uses the wedge technique. The pre-stressing-force can be applied fast and simple and the device is removed after the strip was glued in the groove. As a final step, the pre-stressing device will be removed and a permanent bond anchorage made of epoxy reisin will be implemented. No corrosive anchoring parts remain at the structure, the method is very durable and efficient and furthermore anchorage costs are diminished. The pre-stressing device and strengthening method were developed and tested within the scope of the research project 'Strengthening with pre-stressed near surface mounted CFRP-Strips' conducted at Vienna University of Technology. [ABSTRACT FROM AUTHOR]

Regular structural assessments of tunnel linings are commonly performed by visual inspection. Crack phenomena and their development over time are essential indicators of changes of the stress regimen. These are the most prominent input data for the structural assessment of linings. Cladding for fire protection or noise control inhibit visual inspection and call for alternative methods of crack detection and monitoring. This paper presents the application of an alternative method which employs distributed fibre optic sensing (DFOS) which is installed on already existing linings. The objective is to obtain monitoring results with best reliability in comparison to conventional inspection. While the application of DFOS with fibres embedded in new linings has already been tested extensively, later installation on existing linings poses various challenges. Based on findings obtained from laboratory and field tests in an operational highway tunnel, we found that by means of later installed fibres with lengths of up to 70 m, strain measurements can achieve accuracies of about 1 µm/m over 10 mm. This allows the detection of both current and historical crack widths at 0.01 mm precision, conspicuous strain patterns and temperature abnormalities. The system can be mounted onto the inner lining surface which is covered by later claddings and are hence inaccessible to visual inspection. The structural performance can eventually be inferred from interpreted crack patterns. [ABSTRACT FROM AUTHOR]

After the failure of a cantilever retaining wall with counterfort on the Brenner Autobahn, intensive investigation of existing structures showed considerable corrosion damage to cantilever walls with and without counterforts, at the location of construction and day joints. This is difficult to detect and assess due to the placing of the main reinforcement at the back of the construction. The present paper presents a monitoring concept, which enables detection of corrosion damage and also provides a gain of information about the behaviour of the structure. The basis for this concept is the installation of inclination and strain gauges on the front of a retaining wall. In order to explain the functioning of the concept, a rudimentary cantilever model of the effect of corrosion damage is first described. Then the results and findings from a test series with artificial corrosion representation to reinforced concrete structures to validate the presented monitoring concept is described. [ABSTRACT FROM AUTHOR]