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Considering that existing shaking table tests on bridge structures have not taken into account the effect of moving trains, this paper takes a multi-span simply supported girder with a CRTSII slab ballastless track system and a Chinese CRH2C high-speed train as its objects of study, builds a reduced-scale model for the bridge and train using a simi...
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Passenger riding comfort is a major concern in railways, particularly in high-speed (HS) networks due its strict requirements. Both the track and vehicle conditions may influence the comfort experienced by the passengers, but other external factors may also do it. Among these factors, the effects caused by crosswinds stand out due to the high level...
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... The impact of the track construction on the bridge's seismic resistance cannot be ignored, as the track bears a part of the ground vibration conveyed by the foundation under an earthquake. To ensure train running safety is not only of significant theoretical importance but also holds practical engineering value [4][5][6][9][10][11]. ...
... By constructing a scaled basic girder bridge on a shaking table testing system [11], quasi-distributed fiber-optic gratings were installed at the track plates of the scaled bridge's mid-span section, respectively, to measure strain response in various directions along the same line. ...
In addressing the challenges of analyzing seismic response data for high-speed railroads, this research introduces a hybrid prediction model combining convolutional neural networks (CNN) and long short-term memory networks (LSTM). The model's novelty lies in its ability to significantly improve the precision of fiber grating monitoring for high-speed railroads. Employing quasi-distributed fiber optic gratings, seven grating monitoring points were strategically placed on each fiber to capture responses of the track plate, rail, base plate, and beam during seismic activities. Using data from peripheral gratings, the model predicts the central point's response. A continuous feature map, formed via a time-sliding window from the rail's acquisition location, undergoes initial feature extraction with CNN. These features are then sequenced for the LSTM network, culminating in prediction. Empirical results validate the model's efficacy, with an RMSE of 0.3753, MAE of 0.2968, and a R² of 0.9371, underscoring its potential in earthquake response analysis for rail infrastructures.
... Meanwhile, the scaled earthquake excitation is converted by prototype earthquake excitation (time scaling according to a similar coefficient). Table 1 The similarity coefficients for TRTS (all data refer to [28]). ...
... Structural material of the scaled model (all data refer to [27] constitutive relation of materials and the mechanism of model fabrication can refer to literature [26][27][28]. ...
... Meanwhile, energy transfer occurs between the two lasers. The Brillouin frequency shift Δν B in a standard single-mode fiber can be expressed as [57] Δν B = 2nV a λ (28) Where n is the refractive index of the fiber core, V a represents the acoustic wave velocity, and λ means the wavelength of the laser source in vacuo. ...
... In order to study the impact of a train on a bridge vibration, Chen et al. analyzed the seismic response of different piers under different speeds [4]. Yu et al. studied the influence of train and ground motion on the deformation of the beam, bearing and pier based on the simulation model verified by shaking table experiments [37,38]. Gao et al. considered the incident angle of seismic waves. ...
The probability of a train running over a bridge when an earthquake occurs is increasing with the total mileage of China’s high-speed railway network expanding. To study this issue, a three-dimensional train-track-bridge dynamic interaction system subjected to seismic excitations is established based on commercial mathematical software. Besides, a set of motion equations of the system are derived according to the multibody dynamics, the finite element method theory and the bridge seismic theory. Moreover, in order to study the dynamic response of high-speed railway bridges under earthquake, a series of experiments are conducted on a scaled high-speed railway simple supported bridge model with a ballastless track slab excited by shaking table tests. Meanwhile, the strain of rails, track slabs, base plates and girder in various working conditions are measured by quasi-distributed optical fiber sensing stuck in bridge members. At last, the dynamic response of each structure member is demonstrated in the time and frequency domains. Furthermore, the seismic isolation performance of bridge members, such as fasteners, cement asphalt (CA) mortar layer and so on, is explained in details.
... The assumption of pulse type excitation captures many of the corresponding ground motions' characteristics and allows for parametric numerical studies of structures where the relationship between the structural period and the pulse period can be explored. The impacting responses of beams [23][24][25][26][27][28] and plates [29], impact analysis of the multi-span [30][31][32] and simply supported beam bridges [33,34] are also performed with dimensional [35][36][37] and non-dimensional parameters [38,39]. However, the nondimensional form of governing equation of motion and the corresponding dynamic responses, such as displacement and velocity response spectra for the impact structures, in a more simplified manner with appropriate mathematical formulations, do not exist in any state-of-the-art. ...
The oscillation due to vibration results in impact of the structures if the at-rest separation is insufficient to accommodate the relative displacements. The impact between the floors of the two adjacent buildings or the impact between adjacent decks and abutments is modeled by an impact oscillator subjected to closed-form mathematical formulations of near-fault earthquake motions as pulse-type excitation, such as cosine (±) and sinusoidal pulses (±). This study investigates the impacting responses of an impact oscillator against a barrier from an analytical perspective. The momentum-based stereo-mechanical method is used as a contact force-based model to perform the impact analysis. The equation of the motion of the impact oscillator under lateral pulse-type base excitation is non-dimensionalized by two dimensionless parameters using the standard process of non-dimensionalization of a differential equation. The system has been analyzed for the complete forced vibration part as it was excited by a single cycle of cosine and sinusoidal pulses. However, the transient solutions are also derived for the analysis. Therefore, the free vibration phase is determined until the impactor comes to a non-impacting state. The steady-state with the transient solutions for the complete impacting responses are provided for the exact solutions of the dynamic responses of the impact oscillator, such as displacement response spectra, velocity response spectra. The governing system parameters, such as damping ratio, frequency ratio of the impact oscillator, the coefficient of restitution, and the direction of the base excitation ( ±) are the governing system parameters to control the impact between the oscillator and barrier. A frequency point under resonance region from each response spectra of impact oscillator subjected to cosine ( ±) and sinusoidal pulses ( ±) is subtracted to define the non-dimensional time domain responses. The exact impact determines in out-of-phase state and the dynamic responses of impact oscillator are attenuated. The non-dimensional relative distance between the impacting oscillator and the barrier varies from 0.5 to 3.0. However, for δ~>3, no successive impact obtains. Accordingly, the impacting oscillator’s dynamic response spectra closely match the linear oscillator’s dynamic response spectra. All the results are mathematically derived and accurate for practical applications of a damped impact oscillator (i.e., precisely for single-degree-of-freedom systems) to determine the non-dimensional dynamic responses.
... We have discussed previously 1 that studies of railway systems subjected to earthquake motions were focused mainly on two considerations: (1) seismic analysis of systems where the effects of the bearings are ignored or highly simplified, [2][3][4][5][6][7] and (2) base isolation of railway bridges where the running train is not considered. [8][9][10][11][12] Despite that, several studies using simplified train-bridge-bearing system models have been able to provide an understanding of the bearings' effects. ...
This paper presents numerical studies using the model of the three-dimensional train-wheel-bridge-bearing (TWBB) system. The system responses under train-induced excitation only, earthquake excitation only, and combined train-induced plus earthquake excitation, are evaluated in terms of structural safety, running safety and ride comfort. By coupling the subsystem models, these numerical simulations require just seconds to execute, exhibiting high computational efficiency. Based on the simulation results, the main conclusion is that although the bearings may reduce the seismic bridge responses, they also are likely to deteriorate the train's running safety and ride comfort. Therefore, there is a requirement in future bearings design procedures for railway bridges to find a balance between the bridge and train seismic responses.
... Konstantakopoulos et al. [12] analyzed the dynamic properties of long-span suspended bridges subjected to earthquake motions and moving loads from the train. Yu et al. [13,14] carried out experimental and theoretical studies on the seismic responses of a 1/10 scaled multispan simply supported bridge with a scaled train running through it. These studies could help us to understand the train-track-bridge system's seismic behaviors. ...
Bearing effects have not been deeply investigated in the dynamic analysis of a train-bridge coupled system subjected to earthquake motions, and existing studies on base isolation of railway bridges have typically not considered the running train. To fill these gaps, this paper develops the numerical model of a three-dimensional train-wheel-bridge-bearing (TWBB) system for seismic analysis. The substructuring method is implemented to separate the TWBB system into the train, wheel-rail, bridge and bearing subsystems, and couple them using state-space representations. The complete model of the TWBB system has three main features: fewer degrees of freedom than traditional finite element methods, applicability to different types of bearings, and simplicity as no iterations in the simulation are required. Therefore, the proposed procedure demonstrates that the TWBB model is an efficient and flexible representation to obtain and predict realistic demands for engineering purposes
... Yu and Lai undertook much research [4,8,9,30] on the spectrum representation of earthquake-induced rail deformation through the ANSYS modeling and shaking table experiment [31]. They inputted a large number of earthquake samples, and proposed a simply supported bridge earthquake-induced irregularity spectrum by combining hypothesis testing with Fourier transform for the study of the running safety of trains after earthquakes. ...
As a type of urban life project in China, bridges need a certain capacity of trains running safely after an earthquake to ensure and guarantee transportation on railway lines, post-disaster reconstruction and relief work. Since aftershocks may occur after the main shock, the earthquake-induced irregularity and aftershock intensity are fully considered, based on the running safety index in the seismic design of bridges. However, there is a lack of research on the running safety of trains after an earthquake; it is mainly judged on experience, and lacks theoretical basis. In this paper, the established finite element model of a train bridge interaction system with symmetry was considered. The point estimation method (PEM) combined with moment expansion approximation (MEA) is used for random calculation of the Housner Intensity (HI). Furthermore, running safety indexes were analyzed and the running safety performance of a simply supported bridge with symmetry was assessed under a post-earthquake condition. Then the limit value, to ensure the traffic safety performance after an earthquake, is calculated based on stochastic analysis. The HI can be calculated with full consideration of the randomness of aftershock intensity and structural parameters. On this basis, a calculation method of the HI that considers the randomness of aftershock intensity is proposed. This study can be helpful for the performance-based design of symmetric railway structures under post-earthquake conditions.
... FEM was compared with the shaking table test conducted by Yu et al. 23,24 In the test, the scale model (length similarity ratio is 1:10) of 11-span high-speed railway bridge with CRTS II track system was fabricated. The scaled model was subjected to seismic excitation by shaking the table, and seismic responses of the model were recorded. ...
Railway transportation, as an important lifeline during earthquake relief and post-disaster reconstruction, has an extremely significant role. The study of track irregularity caused by earthquakes is the basis for ensuring traffic safety after their occurrence. In this paper, a finite element model of a five-span simply supported high-speed railway beam bridge with the China Railway Track System (CRTS) II was established and an experimental verification was performed. Eighty arbitrarily selected seismic waves were extracted from the Pacific Earthquake Engineering Research Center (PEER) strong ground motion database and a nonlinear time-history analysis was performed on the finite element model. The frequency–domain distribution law of earthquake-induced track irregularities was studied. A stable target earthquake-induced track irregularity spectrum model was constructed, and its expression was fitted. According to the results, in the case of transverse earthquakes, the rails experienced noticeable alignment irregularity and cross-level irregularity, while the amplitude of the gauge and vertical irregularity were relatively small. The target irregularity spectrum has a higher amplitude in the low-frequency components. When peak ground acceleration (PGA) was low, earthquake-induced track irregularity was not obvious, but the deteriorating effects of earthquakes on track irregularities increased significantly with increasing PGA.
... In addition, the railway bridge-track system has a complex seismic response, and the track structure is prone to damage [26,27]. The higher requirements for the running safety of the upper track structure require a more detailed analysis of the track damage on the railway bridge [28][29][30]. Wei et al. [31,32] used consistent seismic inputs to study the seismic fragility of the CRTS-II track system under different ground motion angles and seismic isolation bearings. Some other researchers [4,33] carried out nonlinear dynamic analysis studies on the CRTS-II track system on the irregular bridge based on the uniform seismic input. ...
To explore the effect of canyon topography on the seismic response of railway irregular bridge–track system that crosses a V-shaped canyon, seismic ground motions of the horizontal site and V-shaped canyon site were simulated through theoretical analysis with 12 earthquake records selected from the Pacific Earthquake Engineering Research Center (PEER) Strong Ground Motion Database matching the site condition of the bridge. Nonlinear seismic response analyses of an existing 11-span irregular simply supported railway bridge–track system were performed under the simulated spatially varying ground motions. The effects of the V-shaped canyon topography on the peak ground acceleration at bridge foundations and seismic responses of the bridge–track system were analyzed. Comparisons between the results of horizontal and V-shaped canyon sites show that the top relative displacement between adjacent piers at the junction of the incident side and the back side of the V-shaped site is almost two times that of the horizontal site, which also determines the seismic response of the fastener. The maximum displacement of the fastener occurs in the V-shaped canyon site and is 1.4 times larger than that in the horizontal site. Neglecting the effect of V-shaped canyon leads to the inappropriate assessment of the maximum seismic response of the irregular high-speed railway bridge–track system. Moreover, engineers should focus on the girder end to the left or right of the two fasteners within the distance of track seismic damage.
Sudden earthquakes pose a threat to the running safety of trains on high-speed railway bridges, and the stiffness of piers is one of the factors affecting the dynamic response of train-track-bridge system. In this paper, a experiment of a train running on a high-speed railway bridge is performed based on a dynamic experiment system, and the corresponding numerical model is established. The reliability of the numerical model is verified by experiments. Then, the experiment and numerical data are analyzed to reveal the pier height effects on the running safety of trains on bridges. The results show that when the pier height changes, the frequency of the bridge below the 30 m pier height changes greater; the increase of pier height causes the transverse fundamental frequency of the bridge close to that of the train, and the shaking angle and lateral displacement of the train are the largest for bridge with 50 m pier, which increases the risk of derailment; with the pier height increases from 8 m to 50 m, the derailment coefficient obtained by numerical simulations increases by 75% on average, and the spectral intensity obtained by experiments increases by 120% on average, two indicators exhibit logarithmic variation.
