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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]

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]

The eigenfrequencies of a bridge are influenced by the environment and by structural integrity. The task of damage identification is to conclude structural integrity from measured eigenfrequencies. Environmental frequency changes are a negative effect that hinders reliable damage identification. In this paper, it is experimentally shown how temperature and traffic load affect the eigenfrequencies, and reduction of this effect using a frequency prediction model is presented. Random variations are described using a probability density function, and a damage indicator based on this function is proposed. The paper addresses the issue of reliability of damage detection considering random and systematic errors that are present in the eigenfrequencies extracted from measurements. Various damage scenarios are presented, both with identifiable and non-identifiable damages. [ABSTRACT FROM AUTHOR]

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]

Assessment of both condition and reliability of engineering structures is essential for appropriate infrastructure maintenance. In particular, changes in geometry (i.e. deformation) are an essential feature of structural condition. Among recent developments of scanning methods that have opened up new possibilities for contactless and rapid measurement of structural geometry, methods based on satellite synthetic aperture radar (SAR) interferometry are especially suitable for precise surface deformation monitoring. By exploiting information contained in the phase values of co-registered, multi-temporal SAR imagery, ground deformation and corresponding displacement rates can be obtained with sub-centimetric precision.With the launches of Sentinel-1A and 1B in April 2014 and April 2016 respectively, C-band SAR data with a spatial resolution of 5×20 meters (Interferometric Wide Swath Mode) became freely available across large parts of the globe. The constellation of the two satellites entails a repetition time of 6 days, and resulting data are provided near-real time.Within the scope of a feasibility study, the general applicability of Sentinel-1 InSAR imagery for monitoring infrastructure assets is evaluated. Specifically, focus has been put on the assessment of the structural health of bridges in terms of deformation rates obtained by means of persistent scatterer interferometry (PSI). This differential interferometric SAR technique relies on strong reflecting objects that are constant over time, and can be used to obtain deformation time series and the deformation velocity estimated over the analysed permanent scatterer points.Bridge deformation monitoring tests are conducted at selected structures along the Austrian primary road network. Estimated permanent scatterer elevations are validated against in-situ measurements (ground truth). In addition, performance of Sentinel-1 based PSI is tested against ground-based measurements of the road geometry (i.e. changes in the longitudinal profile obtained via laserscanning) as well as UAV-based LiDAR measurements.Preliminary results confirm the general applicability of Sentinel-1 SAR data for bridge monitoring in Alpine terrain. At the same time, certain challenges related to selection of persistent scatterers, topographic phase correction as well as atmospheric correction still need to be overcome. [ABSTRACT FROM AUTHOR]