•A unified system is developed to identify and localize structural components and their damage.•Synthetic environments are used to produce datasets that are lacking in general.•Visual recognition ...algorithms trained using the synthetic data can perform the structural condition assessment tasks both for synthetic and real-world images.•Trained networks are combined to realize the unified system for structural condition assessment.
Civil infrastructure condition assessment using visual recognition methods has shown significant potential for automating various aspects of the problem, including identification and localization of critical structural components, as well as detection and quantification of structural damage. The application of those methods typically requires large amounts of training data that consists of images and corresponding ground truth annotations. However, obtaining such datasets is challenging, because the images are annotated manually in most existing approaches. With the limited availability of datasets, development of effective visual recognition systems that can extract all required information is not straightforward. This research leverages synthetic environments to develop a unified system for automated vision-based structural condition assessment that can identify and localize critical structural components, and then detect and quantify damage of those components. The synthetic environments can produce images and associated ground truth annotations for semantic segmentation of structural components and damage, as well as monocular depth estimation for structural component localization. To illustrate the approach, automated vision-based structural condition assessment of reinforced concrete railway viaducts for a Japanese high-speed railway line (the Tokaido Shinkansen) is explored. The effectiveness of the synthetic environments and the generated dataset (the Tokaido dataset) is demonstrated by training fully convolutional network-based semantic segmentation and monocular depth estimation algorithms, and then testing the networks using both synthetic and real-world images. Finally, all trained algorithms are combined to realize an automated system for structural condition assessment.
Das Chemnitzer Viadukt wurde zu Beginn des 20. Jahrhunderts erbaut und über die letzten Jahre denkmalgerecht ertüchtigt. Hierfür war u. a. eine Begutachtung zur Wiederverwendung der aus einzelnen ...Gussbauteilen bestehenden Lager erforderlich. Die Begutachtung umfasste übliche zerstörungsfreie und zerstörende Prüfungen sowie numerische Berechnungen zum Nachweis der Tragfähigkeit. Als neuartige Ergänzung wurden Gusssimulationen, 3D‐Scans der Lager zur Erfassung des tatsächlichen Zustands sowie bruchmechanische Untersuchungen zur Bewertung der Sprödbruchgefahr und des möglichen Rissfortschritts durchgeführt. Unter anderem stellten teils schwere Zugänglichkeit und komplexe Belastungszustände eine Herausforderung dar. In diesem Aufsatz werden das Lagerkonzept und die Methode der Begutachtung vorgestellt sowie die einzelnen Bestandteile mit zugehörigen Ergebnissen beschrieben. Durch die Begutachtung konnte eine Weiternutzung eines Großteils der Lagerbauteile ermöglicht werden.
We have proposed a method for identifying the natural frequency of single structures from data obtained by measuring the vibration of railway bridges and viaducts. With this method, the natural ...frequency of a single structure can be theoretically calculated using undamped natural frequencies and the natural modes of whole structures. The eigenvalue analysis shows that the natural frequency of a single structure can be identified by the proposed method.
•Review of the most important Rail Expansion Devices used in railways bridges in Spain.•Theoretical and field analysis of some of these Rail Expansion Devices (REDs).•Analysis of the existing REDs of ...forty-four bridges and viaducts on the Spanish High-Speed Railway.•Recommendations for design, construction and maintenance of REDs.
The use of rail expansion devices (RED) interrupts the continuity of the welded rail, causing an irregularity with the consequent reduction in comfort, but with the benefit of a significant stress reduction in the rails. Currently the Spanish Railway Administrator uses three types of RED according to their range: 300 (small RED), 600 (medium RED) and 1200 mm (large RED) for all railway structures in the network. Their use has led to the construction of railway bridges and viaducts of maximum free expansion length of just over 1100 m. Development of new high-speed railway lines increasingly demands longer structures. Thus, the maximum allowed free expansion length should be increased. This problem can be faced from two fronts: (1) the improvement of the performance of REDs by developing new designs and (2) the enhanced prediction of the bridges and viaducts real movements caused by retraction, creep and temperature. It is precisely this last approach that has been developed by analysing and reviewing some existing structures. Forty-four bridges and viaducts on the Spanish High-Speed Railway network. Specifically, the railway Lines Madrid-Barcelona, Cordoba-Malaga and Madrid-Valladolid, have been analysed to know the degree of strain of the existing REDs. With these measurements, the possibility of increasing the length of maximum free expansion of the deck has been examined and it has been proven to be possible as predicted strains were higher than the measured ones. Recommendations given have served to developed longer railway structures in Spain.
Viaducts built in cities all over the world can increase their traffic capacity. Yet whether specific dispersion and reduction strategies for traffic-related pollutants, such as ultrafine particles ...(UFP), fine particles (PM2.5), and black carbon (BC), are needed in urban residents' activity areas is uncertain. Here we investigated the distribution patterns of traffic-related pollutants near a viaduct having various infrastructures. Measurements were taken using mobile devices in three sampling sections alongside and extending away from the viaduct in Xi'an, China. Difference-in-differences analysis was used to explore the mitigation effect of noise barriers. The results showed that the pollutant distribution profiles behind both noise barriers and combination barriers (i.e., solid noise barrier plus tree vegetation) are characterized by a novel, unimodal mode whereby the UFP and PM2.5 concentrations first increased and then decreased. Lower traffic-related air pollutant concentrations were observed on the lee side of the noise barrier than at the non-barrier site section. Evidently, compared with a noise barrier alone, the mitigation effect upon UFP, PM2.5, and BC near a viaduct is greater when barrier types are combined, enabling concentration reductions of 5% (UFP), 21% (BC), and 50% (PM2.5). In addition, this study also observed lesser reductions of the three pollutants at greater wind speeds. However, conditions did occur when pollutant concentrations were higher behind a barrier than when no barrier was present, namely when the wind speed exceeded 0.8 m•s−1. Overall, our findings suggest beneficial effects of noise barriers and combination barriers for mitigating the air pollution near viaducts.
•The impact of noise barriers on UFP, PM2.5 and BC in a near-viaduct environment was estimated in a field experiment.•UFP and PM2.5 concentration distribution profiles displayed a new trend: first increasing and then decreasing.•Spatial difference-in-differences analyses were used to evaluate the mitigation effect of noise and combination barriers.•The mitigation of UFP, PM2.5 and BC near a viaduct with combination barriers are more effective.
Abstract
Seismic isolation design is an effective and economical method to protect precast viaducts from severe earthquake damage. Correct selection of bearings is one of the common methods to ...achieve this goal. In order to optimize the vibration isolation performance of prefabricated viaducts, this paper compares the vibration isolation performance of lead rubber bearings (LRB) and laminated bearings (LB). The lead rubber bearing (LRB) and laminated bearing are respectively applied to the same analysis model of prefabricated viaduct. The seismic responses of bearings and structural members are analyzed by dynamic analysis method, and the typical seismic responses, including internal force, displacement, hysteresis curve and residual deformation, are compared. The results show that LRB has higher isolation efficiency and better self centering ability.
Abstract
Facing the difficulty of construction of viaducts in the central area of the city with short construction period and large daytime traffic. Relying on the Nairobi Airport viaduct project in ...Kenya, the problems in the construction of this project and the special seismic intensity of the area were analyzed. The key technologies in the design and construction of the bridge substructure using prefabricated assembly technology were studied, and a reasonable substructure analysis was put forward. Block principle and assembly connection plan, and focus on the key construction technology of pier column and cap beam assembly. Through the research on the key technology of substructure design and prefabrication assembly and the application of engineering examples, the problem of viaduct construction in urban restricted road sections in the earthquake zone with moderate intensity is effectively solved.
•State-of-the-art review on train running safety on bridges.•International normative criteria regarding the train running safety on bridges.•Review of the main derailment mechanisms and safety ...criteria.•Effects of natural hazards, crosswinds and earthquakes, in the train stability.•Influence of track defects and induced deformations in the train stability.
Train running safety is a major concern among railway engineers, since a derailment may cause significant personal and material damages. This problem becomes more important if the derailment occurs on bridges, especially at high-speeds, where the consequences may be even worse. The sudden development of high-speed (HS) railway networks that occurred at the end of the 20th century and beginning of the 21st century demanded the construction of new lines with large curve radii in order to fulfill the design requirements of this type of transport. By adding this fact to the orography constraints and, in some cases, to constraints related with the lack of construction area and with the high costs of expropriation, several HS lines started to be developed with more than 75% of their length built over viaducts and bridges. Naturally, this relatively new reality led to a significant increase in the probability of a train being exposed to natural hazards that might jeopardize its stability when it is running over an elevated structure. Hence, this paper aims to present a comprehensive literature review of the problematic associated with the train running safety assessment on bridges. The existing normative criteria from different regions of the world related to this topic are summarized in a first stage. Then, the paper gives a brief description of the available train-bridge interaction models needed to explicitly assess the traffic stability, followed by a presentation of the running safety indexes used to assess the derailment risk. Finally, the available applications regarding the traffic stability against different sources of excitation are systematically reviewed and guidance to future research work on this topic is provided.
High-speed railway (HSR) brings convenience to peoples' lives and is generally considered as one of the most sustainable developments for ground transportation. One of the important parts of HSR ...construction is the signaling system, which is also called the "operation control system," where wireless communications play a key role in the transmission of train control data. We discuss in detail the main differences in scientific research for wireless communications between the HSR operation scenarios and the conventional public land mobile scenarios. The latest research progress in wireless channel modeling in viaducts, cuttings, and tunnels scenarios are discussed. The characteristics of nonstationary channel and the line-of-sight (LOS) sparse and LOS multiple-input-multiple-output channels, which are the typical channels in HSR scenarios, are analyzed. Some novel concepts such as composite transportation and key challenging techniques such as train-to-train communication, vacuum maglev train techniques, the security for HSR, and the fifth-generation wireless communications related techniques for future HSR development for safer, more comfortable, and more secure HSR operation are also discussed.
Abstract Traffic noise is the main environmental pollution of the elevated line. In order to prevent and control this noise, it is necessary to understand the spatial distribution of the noise. In ...this paper, the noise monitoring and data fitting of representative points near the Ningbo viaduct are carried out by means of the field test. By setting measuring points at different distances and heights perpendicular to and parallel to the elevated line, the spatial distribution law of noise near the elevated line is studied. The results show that: (1) The noise in the transverse direction of the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the viaduct; (2) The noise along the bridge decreases in a logarithmic curve with the increase of the vertical distance between the measuring point and the intersection; (3) The noise in the elevated direction first increases with the rise of the floor, reaching the maximum on floors 10-12, and the sound pressure on floors 12-20 is basically stable.
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