•The impact test results of the scaled model corresponding to the finite element model were used to verify the accuracy of the adopted material models and contact relationships.•Based on the spatial ...complexity of urban overpasses, the dynamic responses and failure mode of the full-bridge model under non-bottom impact were numerically simulated.•Four comparative models were established to study the effect of the bridge model parameters on impact responses.
Urban viaducts are likely to be subjected to non-ground-level vehicle collisions during their service life period. However, current research primarily focus on vehicle impacts on the bottom of bridge piers. In this research, a full-bridge scale model impact test was conducted to validate the accuracy of the finite element (FE) model. Then, LS-DYNA is used to establish refined vehicle-bridge collision FE models. The dynamic responses and failure mode of the pier impacted by the non-bottom vehicle are investigated. Besides, the effects of bridge structure spatial stiffness, superstructure mass, and double-column structure on the impact responses of bridges are analyzed. The results show that vehicle collisions are characterized by a continuous impact action involving multiple components. The damage to the full bridge model is concentrated in the directly impacted double-column pier, where the head-on column sustains three-point bending damage, the indirectly impacted column sustains bending damage at the top and bottom, and the cover beam sustains tensile shear damage. The non-bottom impact significantly increases displacements and bending moments of the pier while causing a substantial decrease in bottom shear. The impact responses of the pier are greatly influenced by the superstructure mass and double-column structure, while the spatial stiffness of the bridge has minimal affection.
To investigate the effects of a trapezoidal sleeper track (TST) on the vibration and noise of rail transit viaducts, the wheel–rail interaction model was first built according to the vehicle–track ...coupling dynamics theory. Subsequently, the vibration responses of the viaduct were analyzed using the beam–slab finite element method, and its radiated noise was calculated using the acoustic boundary element method. The modeling method was verified based on the test data of a 3 × 40 m continuous rigid frame bridge. Taking the Jialing River Bridge of Chongqing Rail Transit Line 9 as the background, the control effects of the TST on the vibration and noise of the viaduct and the effective laws of different track parameters on the bridge noise were analyzed. Results show that the simulated and measured values are in good agreement; for example, the modeling methods are reliable; the radiated noise of the viaduct is influenced by the vibration responses under the action of train load, which are jointly determined by dynamic wheel–rail force (external excitation) and displacement admittance (self-vibration characteristics); compared with embedded sleeper track (EST), the TST can reduce the overall vibration acceleration level and sound pressure level of the box girder web plate by 13.9 dB and 7.8 dB, respectively; the stiffness of the damping path is the primary factor influencing the noise of the elevated box girder, followed by the sleeper thickness and the fastener stiffness; taking the bottom plate as an example, the stiffness of the damping pad is reduced by 1 and the overall sound pressure level can be reduced by approximately 3 dB; the sleeper thickness is increased by 1, and the overall sound pressure level can be reduced by 1–2 dB; and the fastener stiffness is reduced by 1, and the noise reduction is within 1 dB.
This paper reports (i) a set of measurements of the wireless propagation channel at 930 MHz, conducted along the "Zhengzhou-Xian" high-speed railway of China in various railway viaduct scenarios, and ...(ii) an analysis and modeling of the small-scale and large-scale channel parameters based on those measurements. The environment can be categorized into four cases, covering viaducts with different heights and in different suburban environments. Small values of fade depth, level crossing rates, and average fade duration are observed. Akaike's Information Criterion (AIC)-based evaluation indicates that the Ricean distribution is the best to describe small-scale amplitude fading. An analysis of the envelope autocovariance function shows that the coherence distance is less than 10 cm. The Ricean K-factor is modeled as a piecewise-linear function of distance. Moreover, a breakpoint path loss model is developed and shadow fading is investigated using the same break point as for the distance-dependent K-factor model. The Suzuki distribution is found to offer a good fit for the composite multipath/shadowing channels. We find that the viaduct height H, together with the number of surrounding scatterers, significantly affects the small- and large-scale channel parameters. These results are applicable to both normal-speed and high-speed railways, and will be useful in the modeling of railway viaduct channels and the design of railway wireless communication systems.
Rapid transit or mass rapid transit (MRT) is a high-capacity public transport designed to carry a large number of passengers, especially during the peak hours. They are becoming very popular in major ...cities and some deem the presence of the rapid transit system in a city as a symbol of modern development and essential feature of urban life. As the rapid transit system expands, the traveling time on a rapid transit train may increase due to longer journey and cabin noise has become an environmental concern for the passengers. In the present study, we would attempt to do a more detailed study of the effect of viaduct height, in particular viaducts of different heights on the cabin noise of various rapid transit systems. The present study examined and benchmarked the cabin noise in terms of both dB(A) and dB(C) for four different rapid transit systems, namely part of the East-West line including the Tuas-West extension on elevated tracks with very high viaduct of the Singapore MRT System; part of Paris Line 2 from Anvers to Belleville station including a stretch of elevated track on viaduct; part of the Piccadilly line of London from Heathrow Airport to Green Park station with a stretch on surface ground; and finally part of Chongqing Line 3 from Gongmao to Lianglukou station across the Yangtze river. It was found that the cabin noise would be dominated by low-frequency content and would be better reflected if the measurements were presented in dB(C), especially for trains running on elevated tracks of greater height.
Das Chemnitzer Viadukt wurde für viergleisigen Betrieb mit einer Länge von 275 m in den Jahren 1901–1909 errichtet. Nach 120 Jahren der Nutzung musste es technisch instand gesetzt und für eine ...zeitgemäße Nutzung auf weitere 80 Jahre ertüchtigt werden. Der Brückenzug aus vier parallelen Überbauten verläuft über zwei Bögen und zehn Felder mit Vollwandträgern. Für die zukünftige zweigleisige Nutzung wurden die beiden inneren Überbauten mit Gleisen für den Schienenverkehr ausgestattet, die beiden äußeren Überbauten zur Unterbringung von Rand‐ und Rettungswegen sowie der technischen Ausstattung verwendet. Dafür wurden die inneren Balkenbrücken erneuert und als Stahlverbundkonstruktion ausgeführt. Die Unterbauten und sonstigen Überbaukonstruktionen wurden, entsprechend den Anforderungen des Denkmalschutzes, weitestgehend erhalten und nach Erfordernis saniert bzw. kleinteilig ausgetauscht. Ein besonderes Augenmerk lag auf dem Erhalt der Vielzahl historischer Stahllagerkonstruktionen. Die bauliche Umsetzung dieses komplexen Vorhabens unter „rollendem Rad“ erforderte besondere Maßnahmen für den laufenden Bahnbetrieb. Im vorliegenden Beitrag wird nach einer Übersicht zum historischen Bauwerk und dessen Bewertung auf die für dieses Projekt hervorzuhebende Arbeit im Fachbeirat eingegangen und im Weiteren der Umgang mit verschiedenen Maßnahmen zur technischen Instandsetzung und Verstärkung unter Berücksichtigung des Denkmalschutzes in Verbindung mit einigen zusätzlich erforderlichen Genehmigungen und Zustimmungen im Einzelfall erläutert.
Translation
Strengthening planning for the Chemnitz Viaduct from the perspective of the checking engineer
The Chemnitz Viaduct was built for four‐track traffic with a length of 275 m between 1901 and 1909. After 120 years of use, it had to be technically repaired and strengthed for the use for another 80 years. The bridge consists of four parallel superstructures, each spans over two arches and ten beam bridges. For future double‐track traffic, the two inner superstructures were equipped with tracks for rail traffic, and the two outer superstructures were used for side and emergency sidewalks as well as for technical equipment. For this purpose, the inner beam bridges were replaced and designed as a steel composite structure. The substructures and other superstructures were largely preserved in accordance with the requirements of monument protection and renovated or replaced in small parts as necessary. Particular attention was paid to preserving the large number of historical steel bearings. The structural implementation of this complex project under “rolling wheels” required special measures for ongoing railway traffic. In this article, after an overview of the historical building and its assessment, the work in the advisory board is discussed and the handling of various measures for technical repairs and strengthenings, taking into account the monument protection in conjunction with the additional necessary permits and approvals.
Many conveniences and efficiencies have been brought to the passengers with the rapid growth and application of High Speed Train (HST), especially in China. However, the vibrations induced by HST can ...cause adverse influences on the surrounding environment, which arouses increasing concerns from researchers and governments. In this paper, in-situ HST generated ground vibrations were measured in the embankment, culvert, viaduct and transition sections of Beijing-Shanghai high speed railway (HSR) in China. The acceleration responses of the free field in three directions (x, y, z) were recorded with a train operation speed of around 250–350km/h. The characteristics of the three directional free field responses in time and frequency domains are then be acquired. Moreover, the variations of vibration amplitude and its vibration level with the distance from the track centerline and train speed are investigated, respectively. Ground dynamic impact coefficient (GDIC) and ground remaining dominant frequency (GRDF) are first introduced and defined to identify the ground vibration performances. It is found that the vertical acceleration response is typically the largest in the near field, while in the far field the largest one is the transverse acceleration response. When a culvert or viaduct is included, the longitudinal vibration would be dominant in the near field. Typically, an obvious vibration amplification zone can be observed in the field around 20m due to the wave interference. In all four measurement scenarios, the dominant frequencies of the free field are typically n times the characteristic frequencies, which have a strong relation to the train's geometry dimension and unevenness of the rail. The first dominant frequency of the free field is generally determined by the distance between wheelsets, bogies and the ground fundamental frequency. Some useful recommendations are also provided in this paper and the results are valuable for validating numerical prediction of HST induced vibration and ground-borne vibration mitigation.
•Four scenarios of in-situ HST induced vibrations were conducted.•The ground vibrations in three directions are included.•Ground dominant frequencies are n times the system characteristic frequencies.•The new definitions of GDIC and GRDF are introduced.
Abstract
Der Rückbau vorgespannter massiver Talbrücken auf einer Vorschubrüstung ist ein etabliertes Verfahren, wo konventioneller und sprengtechnischer Rückbau nicht angewendet werden kann. Im ...Erfahrungsbericht werden die Komponenten der Rückbaugerüste beschrieben, Besonderheiten dieser Rückbaumethode und Randbedingungen für den Einsatz von Vorschubrüstungen entgegen und in Herstellrichtung des abzubrechenden Bauwerks benannt sowie die Möglichkeit der Wiederverwendung der Vorschubrüstung für den Ersatzneubau. Schnittstellen zum Bauwerk werden definiert und Hinweise zur Planung derartiger Rückbauprojekte werden gegeben. Anhand des Beispiels Talbrücke Onsbach erfolgt eine Ablaufbeschreibung des Rückbauverfahrens.
Abstract
Experiences with movable scaffolding systems in deconstruction of post‐tensioned viaducts
The deconstruction of post‐tensioned viaducts with a movable scaffolding system is an established method where conventional and blasting deconstruction cannot be applied. The report describes the components of the deconstruction MSS, the special features of this deconstruction method and the boundary conditions for the use of movable scaffolding systems against and in the direction of construction of the structure to be demolished, as well as the possibility of reusing the movable scaffold for the new construction. Interfaces to the bridge structure are defined and advices are given on the planning of such dismantling projects. Using the example of the Onsbach viaduct, a description of the dismantling procedure is given.
Morandi’s Polcevera viaduct was an important transportation link that connected port of Genoa to other major cities in Europe. The bridge was in service for over 50 years and carried the traffic over ...one of the busiest highways in Europe. Real-time structural health monitoring would have provided data for maintenance and warned of impending failure. The objective of the study reported herein was to estimate the remaining service life and predicting the end of life for the bridge in the absence of available sensor data. The analysis involved time-domain estimation of bridge capacity loss over the period of bridge service and increase in demand over the same period. In addition to the existing information about the bridge, combined effects of corrosion and fatigue were considered in estimating the decrease in the capacity of the bridge from the time it was placed in service. Classical influence line analysis of the individual sections of the pylon–deck system of the bridge, together with the finite element model of the bridge, provided the numerical tool for analysis of the bridge. A number of different approaches were compared in estimating the remaining life of the bridge, including the cumulative damage law of Palmgren and Miner, as well as the Goodman, Gerber and Soderberg mean fatigue stress diagrams. The predicted timing of collapse by these models ranged from the year 2014 based on the cumulative damage law, and 2016 by the Gerber and Goodman diagrams. The estimates from this study predict the collapse of the bridge 2–4 years prior to the actual collapse date in 2018. The results of this study indicated that even without an active instrumented structural health monitoring system, basic engineering principles may provide the backing for estimation of remaining life of the infrastructure. In the case of the Morandi bridge, such an analysis at some point during its service life would have possibly predicted imminence of collapse prior to the actual collapse.
This paper investigates the influence of viaduct, noise barrier, and the ratio of leeward and windward building height (H1/H2) on flow regime and particulate matters (PM) dispersion in an urban ...street canyon, using Computational Fluid Dynamic (CFD) simulation. Results show that viaduct introduces more sources of particulate and influences the flow pattern significantly. New vortexes form when noise barriers set up along the viaduct and influence the flow around the viaduct and distribution of pollutants at the center of the canyon but influence to a less extent in the key breathing zones. When the street canyon is symmetric, barriers can reduce the peak value of pollutant concentration at buildings wall, and lower the integral concentration in zones that affect people's breathing. When the street canyon is a step-up type (the leeward building is lower than the windward one), barriers affect to a less extent the PM distributions at buildings wall and breathing zones. Increase of the height of windward buildings hinders the diffusion of pollutants. Furthermore, people living in the windward building or walking on the street have to suffer more from the pollutant. When the street canyon is a step-down type (the leeward building is higher than the windward one), H1/H2 = 6/5, pollutants still gather at the leeward wall. It has the least integral pollutant concentration in the zone near buildings and street. H1/H2 = 2, pollutants are transported to the windward wall and accumulated because of the upper main vortex in the canyon. Pedestrians' breathing zone is extremely high compared with other configurations.
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•The influence of viaduct, noise barrier, and the building configuration on PM dispersion in street canyon was study.•Viaduct can keep more pollutants within the street canyon and influence the flow pattern significantly.•Noise barriers mainly influence the pollutant distribution at the center of the canyon but less in the key breathing zones.•A higher downwind building than the upwind building can hinder the diffusion of pollutants.
In this paper, the research goal was the determination of the flexural response of corroded pre-stressed reinforced concrete beams (PC). A simplified flexural model is bases on the calcualus of the ...moment and curvature/deflection curves for simply supported beam under uniformly distributed and concentrated loads. Primary research outcomes was the introduction in flexural model of the effects of pitting corrosion though the reduction of area, of the mechanical properties of steel strands and of the loss of bond of steel strands of precast pre-tensioned beams.
A comparison with available experimental data of literature and with numerical simulation carried out with nonlinear finite element code (ABAQUS) was made. Results obtaiend showed that the corrosion of strands reduce the bearing capacity of the viaducts with prestressed beams especially and because of the reduction of strain capacity of steel strand, arises a risk of brittle collapse under service conditions due to the strand failure.
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