1,721,012 research outputs found
Comparative Analysis of Different Models To Estimate the Internal Pressure of a Railway Vehicle Based on Experimental Data
No full textOn situ vibration based structural health monitoring of a railway steel truss bridge: a preliminary numerical study
Full text linkRailway network is subject to increasing travelling loads and traffic frequency. In
addition, since most of the bridges were built in the last century, they are subject to ageing and
degradation. It is therefore necessary to develop proper structural health monitoring systems
that can support periodical visual inspections. In this context, direct monitoring systems
represent an important and promising solution for structural health monitoring purposes. This
paper is the result of a numerical study performed on a 3D FE bridge model based on an
existing structure: the latter is a Warren truss railway bridge, located in Northern Italy, built
few years after the end of the second world war. The purpose of the study is to numerically
evaluate the effectiveness in damage detection and localization of different vibration-based
techniques. This analysis has been performed for a set of different damage scenarios, suggested
by the infrastructure managers
SHM Campaign on 138 Spans of Railway Viaducts by Means of OMA and Wireless Sensors Network
Full text linkA numerical investigation of new algorithms for the drive-by method in railway bridge monitoring
No full textRailway Infrastructure Manager increasingly demand for new and effective method for the monitoring of infrastructure health, so that a relevant effort is being placed in the development of condition based monitoring and maintenance techniques for railway infrastructure. This includes track geometry, overhead contact line and the structural health of railway bridges. This paper proposes an algorithm for the bridge monitoring of railway bridges, based on accelerations measured on board train (drive-by method). The diagnostic algorithm is developed and validated based on the results of a 3D numerical model simulating the dynamic interaction of the bridge/track/train structure. The analysis is focused on steel truss bridges, on which the degradation of the connection of one diagonal element is simulated (e.g. lose bolts, deteriorated welding). In comparison with previous research works, this paper tries to overcome the need of comparison to a reference signal corresponding to the healthy bridge, which is the technique on which most of literature papers rely on. This is achieved by exploiting the roll component of the train (difference between right and left acceleration), excited as a consequence of the presence of the defect which generates an asymmetry in the bridge behavior. The numerical results show good accuracy in damage identification and location, good robustness to vehicle speed, to the presence of electrical noise and, in the case of a relevant damage, to track irregularity
Drive-by methodology to identify resonant bridges using track irregularity measured by high-speed trains
Full text linkResonance of railway bridges is a matter of major concern in high-speed railways because it reduces riding comfort, damages the attached structures, and decreases the strength of girder bodies. Although this abnormal behavior can be inspected using in situ displacement measurements taken from the ground, its investigation is tedious and, consequently, is very expensive. In this study, authors developed a novel drive-by system for high-speed railways to detect resonant bridges; the difference between two track irregularities at the same position using devices mounted on the first and last vehicles of a train was measured. This is based on the idea that the response of the last vehicle passing through the resonant bridge is attributed to the superposition of track irregularities and abnormal bridge displacement because of resonance mechanisms. However, the response of the first vehicle primarily arises from track irregularities since the resonance phenomenon is not yet sufficiently excited. The Resonance Detection Index (RDI), defined as the difference between the track irregularities measured by the devices mounted on the first and last vehicles, is used to emphasize the component excited by vehicle length to propose a methodology for detecting resonant bridges. Numerical simulations clarify that bridge span and track irregularity have greater effects on the RDI than either measurement noise or positioning error. Track irregularity may cause the RDI to vary by ± 2 mm depending on vehicle length wave component of the track irregularity. Consequently, this study demonstrates that resonant bridges with spans between 20 and 60 m can be detected using the proposed RDI. Finally, the proposed method was applied to track irregularity measurements using actual high-speed trains operating in Japan. More than ten bridges, out of more than 800 bridges, were detected as resonant bridges according to RDI. In situ displacement measurements were performed for three of these bridges, demonstrating the presence of resonance phenomenon and thereby validating the proposed method
An application of drive-by approach on a railway Warren bridge
No full textThe present paper illustrates a wavelet-based drive-by methodology to assess bridge health condition, identifying possible damage presence and position. The case study is represented by a single-track, medium span, Warren truss bridge, whose FE model was constructed referring to a real existing structure, and dynamically validated with experimental tests. Vertical bogie accelerations are processed by Continuous Wavelet Transform and the obtained scalogram is sectioned at a specific frequency, associated to the passage of the vehicle over each module of the truss structure. A damage index is then built up starting from the wavelet coefficients referred to this frequency. Therefore, the method exploits the structural conformation of the truss bridge as a tool for detecting damages occurred to its deck. The approach is tested using a 3D train-track-bridge dynamic interaction model: different speeds, track geometrical profiles and damage scenarios are explored to assess the effectiveness of the method and its robustness
Truss Railway Bridge Indirect Frequency Estimation by Time-Shifted Accelerations Difference
No full textIn the field of Structural Health Monitoring the modification of the natural frequencies of an infrastructure can be used for monitoring the occurrence of a damage and to follow its evolution. This paper deals with the identification of the first flexural frequency of a railway bridge from the accelerations measured on board of a transiting train. In a real scenario there are several external disturbances that can affect the effectiveness of any drive-by method, among these there is the track geometrical irregularity. To deal with this issue, the authors propose an approach based on the technique of time-shifted signals subtraction. A mathematical formulation is derived, where the role played by the ratio between shifting time and signal period in the performances of the time-shifted subtraction operation is clarified. To check the method, train-bridge dynamical simulations including track irregularity were performed. As a result, sensing points onboard positioning as well as a sufficient target bridge frequency excitation during train transit emerged as key factors to be met simultaneously for the success of the methodology illustrated in this work
Preliminary evaluation of infrastructure and mobility services in mega-event: the Italian case study
Full text linkMega-events play an important role in the urban agenda of contemporary metropolises. This importance lies in the fact that such events are seen as possible catalysts for the urban development of a metropolis and more generally of a territory, and an opportunity to establish them as global cities. The planning and programming of a mega-event can be a country's showcase on the international landscape, and the mobility sector plays a significant role in defining its success or failure. Transport infrastructure generally requires high resources for both construction and maintenance even after the event. Therefore, in order to ensure a good outcome, it needs to be planned strategically at multiple levels; this condition brings a benefit to both the host city and the community. The main purpose of this study is to analyze a mega event like the Olympic Games by highlighting the relationship between existing mobility solutions and sustainable solutions considering also the surrounding area. This is to enable the creation of new intelligent transportation options. The Olympic Games, in fact, can represent a valuable opportunity to modernize the existing infrastructure of a country by improving the level of service and quality. The study considers, on the one hand, the expected demand for transport during the event and, on the other, the specific features of the different solutions that can be adopted to meet mobility needs
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