Metro Depot Research Articles

Probabilistic Prediction and Assessment of Train-Induced Vibrations Based on Mixture Density Model

This study presents a probabilistic prediction method for train-induced vibrations by combining a deep neural network (DNN) with the mixture density model in a cascade fashion, referred to as the DNN-RMDN model in this paper. A benchmark example is conducted to demonstrate and evaluate the prediction performance of the DNN-RMDN model. Subsequently, the model is applied to a case study to investigate and compare the uncertainties of train-induced vibrations in the throat area and testing line area of a metro depot. After training, the model is capable of accurately predicting the probability density function (PDF) of train-induced vibrations at different distances from the track and at different frequencies. Utilizing the predicted PDF, probabilistic assessments can be performed to ascertain the likelihood of surpassing predefined limits. By employing a mixture density model instead of a single Gaussian distribution, the DNN-RMDN model achieves more accurate prediction of the PDF for train-induced vibrations. The proposed probabilistic assessment framework can effectively assist in vibration screening during the planning phase and in selecting and designing vibration mitigation measures of appropriate levels.

Predicting the Influence of Vibration from Trains in the Throat Area of a Metro Depot on Over-Track Buildings

Urban land resources are scarce in China. To utilize land effectively and economically, many cities are developing over-track buildings above metro depots. The vibration from the entrance and exit lines of metro depots under an over-track platform would significantly impact over-track buildings. To study the influence of train vibration in the throat area of a metro depot on over-track buildings, a simulation model was established using a finite element method. The reasonability of the simulation method and parameter settings was verified through comparing the vibration simulation results with vibration test results in the throat area of a metro depot. Furthermore, the impact of parameters of over-track platform and building on indoor vibration induced by a train was quantitatively studied. According to simulation results, a prediction model was developed to predict the impact of train vibration on over-track buildings in metro depots. From the perspective of architectural planning and design, this study provides a theoretical and technical basis for the prevention and control of indoor vibrations in over-track buildings of urban metro depots.

Mechanical Properties of Adjacent Pile Bases in Collapsible Loess under Metro Depot

Metro transit construction has begun to develop rapidly in northwest China because of the acceleration of urbanization. Accordingly, metro depots are also regarded as an essential auxiliary facility for stopping, operation, and maintenance of trains. Meanwhile, many commercial buildings are constructed over metro depots to improve the utilization rate of land due to the increasingly scarce urban land resources, known as transit-oriented development (TOD). These buildings have a large covered area and transfer concentrated loads to the bases. Therefore, pile bases under metro depots have the bearing characteristics of undertaking large concentrated loads, while lesser loads are placed on the soil between the adjacent pile bases. Additionally, the main ground in northwest China is collapsible loess, so the collapsibility should also be considered. Based on the above background, this research performed static loading tests with and without immersion in a reduced scale of adjacent pile bases under a metro depot in Xi’an. The remolding process of natural loess could destroy its structure and the anisotropy of natural loess could also affect the test results. Therefore, four kinds of artificial collapsible loess with different mass ratios of barite powder, kaolin, river sand, cement, industrial salt, and calcium oxide were made by the free-drop method. This method could make the artificial loess simulate the structure of natural loess reasonably. Then, the artificial loess with the most similar properties to intact loess was selected by comparison. Finally, static loading tests with this artificial loess were implemented. The results showed that the ultimate bearing capacity was 4.5 kN. At the same time, the axial force decreased along depth, since the pile shaft friction was positive, and the load sharing ratio of pile tip force increased to 0.58 when the load exceeded 4.5 kN in the situation without immersion; the settlement of pile bases increased significantly after immersion, while the negative shaft friction occurred at the depth of −8 cm~−35 cm, and the load sharing ratio of pile tip force reached 0.92.

Analysis of Train-Induced Vibration Transmission and Distribution Characteristics in Double-Layer Metro Depot

Analysis of Train-Induced Vibration Transmission and Distribution Characteristics in Double-Layer Metro Depot

Field Test and Numerical Study of Train-Induced Vibration of Over-Track Buildings Above Metro Depot

AbstractTo maximize the use of urban land, many cities have built buildings above metro depots. However, the low-frequency vibration caused by metro operation affects the lives of surrounding residents, which seriously restricts the further development of over-track buildings. To study this problem, Firstly, the vibration of the metro depot and surrounding sensitive areas are tested on a large actual metro depot in Southwest China, and the rail, sleeper/support column, bearing column, and cover plate are mainly tested. Then, considering nonlinear factors such as mechanical properties of building materials, soil layering characteristics, and artificial viscoelastic boundary, the numerical coupled model of the train-track-depot-building is established, and the simulation data are compared with the test data to verify the accuracy of the numerical model. Finally, the impact of metro operation on the over-track buildings is evaluated. Results show that for the over-track buildings concerned in this paper, the floor vibration near the rail is the strongest, the main vibration frequency of the office building is concentrated in 10–20 Hz, and the maximum Z vibration level (VLzmax) of the office building is 52.02 dB. The main vibration frequency of the residential building is similar to that of the office building, and the superposition of floor vibration energy causes the vibration of the mid-span point to be larger than the vibration of the corner point and the side wall point. The vibration wave of lower floors mainly propagates through the bearing column, and the vibration of the parking garage is larger than other buildings. The research results can provide a reference for the vibration control and design of over-track buildings above the metro depot.

Experiment and analysis of train-induced metro depot vibration

ABSTRACT Vibration induced by metro propagates to the building and affects people’s normal life and work, which has become a key factor restricting the development of over-track building. Relying on an over-track building project in Southwest China, vibration experiments are carried out in turnout area, parking area, over-track area and sensitive area of the metro depot. Acceleration and vibration level are selected as indicators to study the propagation law of vibration in depot structure and evaluate the impact of vibration on depot. The vibration amplification phenomenon of the over-track platform is studied and the functional relationship between the vibration amplification position and the wave velocity, frequency, and bearing column spacing is constructed. Results show that the vibrations of the turnout area are obviously greater than other areas, the maximum vibration is 100.3 dB on the rail. In the process of vibration propagating from the rail to the bearing column, the attenuation increases with the increase of distance, and the vibration is attenuated in the range of 1.25 Hz−200 Hz. The phenomenon of vibration amplification exists at the over-track platform, the maximum z-vibration level is amplified by 4.3 dB at most, which is considered to be caused by the vibration superposition in the depot structure. For the structure studied in this paper, the vibrations with frequencies of 10 Hz, 20 Hz, 31.5 Hz, and 63 Hz cause local vibration amplification of the floorslab, and the maximum position of vibration superposition is related to wave velocity, frequency and bearing column spacing.

Vibration transmission model of buildings based on virtual spring model and energy functional variation principle

In recent years, the “metro depot + over-track buildings” development model has witnessed rapid growth in China, driven by its advantages of high land utilization and investment return rate. However, the issue of vibration and noise caused by trains entering and exiting the depot has become a major impediment to its sustainable development. To predict the vibration of over-track buildings induced by trains, this paper presented a vibration transmission model of buildings based on the virtual spring model and the energy functional variation principle. The model was then applied to an actual engineering project at a metro depot in Guangzhou, China, and its accuracy was validated by comparing the results with finite element analysis and field measurements. Additionally, the vibration transmission characteristics of the over-track building were studied. The results indicated that the vibration transmission model of buildings presented in this paper aligns well with the results obtained through finite element analysis and field measurements. This approach eliminates the need to disassemble structural members, and the introduced virtual spring model effectively simulates non-ideal connections and boundary conditions. Consequently, it offers convenient structural connection and boundary condition settings, as well as high computational efficiency. Due to the edge effects on the top floor of the buildings, vibration waves in the higher floors experience a combination of reflected and incident waves, resulting in slow attenuation and, in some cases, amplification of vibrations as they propagate from the middle floors to the top floor. The vibration of the over-track building is closely related to the natural vibration characteristics of the floor and the frequency spectrum characteristics of the vibration source. When the natural frequency of a building's floor aligns with the main frequency of the vibration source, significant vibration amplification occurs due to local resonance.

Floor vibration predictions based on train-track-building coupling model

With the objective of rational urban space utilization, the development of elevated metro depots and over-track buildings is progressing rapidly, with a particular focus on addressing the vibrations caused by trains. Unlike traditional metro depots, trains in elevated depots run on concrete floors, which may lead to excessive floor vibrations. Therefore, it is essential to evaluate the impact of these vibrations during the design phase. In this paper, a vertical vibration prediction model for trains running on building floors is proposed by integrating the train, track structure, and building structure into a unified system. The train model is conceptualized as a multi-rigid body connected by springs and dampers. The track structure comprises rails, fasteners, and track slabs. The building floor is simplified as a rectangular plate composed of multiple orthogonal structural girders and columns in vertical contact with the floor. To verify the proposed method, field measurements were conducted in an elevated metro depot. The proposed model provided estimates of the vibration transmission with good agreement from track to building floor by comparing with the measured vibrations. The model presented in this paper can be utilized to predict the base vibrations of buildings and further predict the floor vibrations.

Study on smoke movement for a fire in a metro depot throat area with different side wall heights

The throat area is an important part of the metro traffic that connects the metro depot and the mainline tunnel. The throat area of 37500 m2 was conducted to investigate smoke movement. The influence of side wall height on smoke movement was considered by combining the theoretical analysis with numerical results. Six sidewall heights including 0 m, 3 m, 5 m, 7.5 m, 9 m, 10 m were designed. The sidewall would have a little impact on free diffusion of smoke when the height of the side wall is lower than 7.5 m. Smoke movement may be affected by the adjacent wall, forming the phenomenon of smoke accumulation when the side height is 7.5 m. It should be considered to expand the openness of the side wall or add mechanical auxiliary smoke exhaust equipment in a local position. This work may provide an engineering reference value for fire smoke control in the throat area of the metro depot.

Assessment of interference scope induced by stray current in the metro depot for the corrosion risk of buried metal pipeline

Assessment of interference scope induced by stray current in the metro depot for the corrosion risk of buried metal pipeline

Evaluation of orderliness of underground workplace system based on occupational ergonomics: A case study in Guangzhou and Chengdu metro depots.

An underground workplace (UGW) is a complex system with multiple subsystems that interact with each other. However, the research on UGW from a systemic perspective has not received due attention. This study constructs an evaluation approach to the orderliness of UGW and systematically evaluates the UGW with Guangzhou and Chengdu metro depots as case studies. First, the evaluation index system is established based on occupational ergonomics. Second, the system entropy model is constructed based on information entropy. Third, a dissipative structure judgment model is built based on the Brusselator. Fourth, the orderliness evaluation model is constructed based on information entropy and synergetics. The UGW of the metro depot has not yet reached the dissipative structure and is in a medium-order state. But the system is in the trend of orderly development. The entropy increase caused by the physical environment and health status is the main obstacle for the system to move toward order. The equipment configuration is an essential source of system negative entropy. The coordination between equipment configuration, health status, and physical environment is low, and that of work effectiveness, equipment aging and failure, and organizational environment is high. Equipment configuration cannot fully cope with the harsh physical environment and meet the needs of underground workers. Safety security equipment has more room for improvement. Humanized support facilities can introduce more negative entropy to the system. Organizational intervention can reduce the negative impact of adverse factors on the system.

Evaluation of indicators of railway-induced annoying vibration based on building measurements developed by TOD: a discussion

The main negative impact of the residential buildings located on the cover structure of a Transit Oriented Development (TOD) metro depot is that residents would suffer from the train-induced annoying vibrations. Arguments accordingly arose on the possibility of evaluating indicators controversy for this application that acceleration data was more captured in the past while velocity would be more related to structure born noise. Therefore, this paper provided a relative comparison based on a measurement campaign that both velocity and acceleration sensors were installed together at the same time. The collected vibration accelerations and velocities are analyzed and discussed using the methods of transmission loss, coherence, and time and frequency domain analysis. The results indicated that even there was no difference for identifying the resonance frequency of structure, but the transit mobility and human annoyance evaluation were obviously different by using velocity or acceleration. Attempts to establish a relationship between the two indicators using the calculus method failed because they showed the largest error at the peak frequency at the same vibration level, which would have affected the evaluation results and the judgment on the choice of mitigation measures.

Risk Assessment of Human Error in Orange-line Metro Depot Operation

Risk Assessment of Human Error in Orange-line Metro Depot Operation

Monitoring and analysis of railway-induced vibration and structure-borne noise in a transit oriented development project

With the rapid development of modern cities, the construction of over-track buildings and buildings along the subway line are increasing gradually. In order to evaluate the influence of rail transit on these buildings, the railway-induced vibration and structure-borne noise of subway stations and buildings in a Transit Oriented Development (TOD) project are monitored and analyzed in this paper. The vibration monitoring data in the subway station shows that the vibration acceleration response of the measuring point in the station caused by the train entering and leaving the station is the largest in the vertical direction, followed by the along-track direction, and the vertical-track direction is the smallest. The corresponding predominant frequency of vibration is usually in the range of 100 Hz-200 Hz. The vibration monitoring data of the building foundation along the subway line shows that the railway-induced vibration of the building foundation along the track near the subway station decreases with the reduction of the distance from the subway station. The monitoring vibration results of the over-track building on the metro depot are different from the buildings near the main line. The predominant frequency of the vibration at the measuring point is in the range of 30 Hz-40 Hz. The small vertical vibration acceleration response of the measuring point corresponds to a high vibration level. In addition, the amplitude of railway-induced vibration in some building rooms near the metro depot is basically consistent with the amplitude of background vibration, but the monitoring value of the structure-borne noise is obviously higher than the background noise. The research results of this paper show the influence of railway-induced vibration on the over-track buildings and the buildings along the subway line, which has important reference value for the comprehensive development of rail transit.

Train-Induced Vibration Prediction and Control of a Metro Depot and Over-Track Buildings

To predict and control the train-induced vibration in depot buildings, a case study of the depot of Tianjin Metro, Line 5, was conducted. The platform of the depot has been constructed and is in use, and the construction of over-track buildings has not been completed. Firstly, an in situ measurement was performed to obtain the train loads and validate the numerical model. Secondly, a finite element model of the track–soil–depot structure was established. The train was simplified as a series of two spring-mass models and the train load was simulated using the measured rail acceleration. The calculated results were validated by the measurement data. To predict the vibration responses of the over-track building to be built, a sub-system of the over-track building was added to the numerical model. Finally, the vibration control effect of vibration isolation bearings was discussed. The results indicate that vibrations exceeded guideline limits without mitigation measures in some rooms of the over-track building. The dominant frequency of the building floors is 31.5 Hz. Vibration isolation bearings effectively mitigated the vibrations, and the IL reached approximately 7–15 dB at about 31.5 Hz.

Study on the Impact of a Metro Depot Cover Structure on the Existing Metro Structure and Additional Settlement of Tracks

The superstructure of the metro depot is not only convenient for traffic but also solves the land-use problem. However, the construction of the superstructure comes after the metro depot has been put into normal operation. The foundation of the depot is bound to produce secondary settlement. Based on the calculation method of the friction-end bearing pile of Mindlin’s solution in the specification, the superstructure construction project above the Beijing Guogongzhuang metro depot is taken as the basis. Under certain conditions, the settlement of the pile foundation under the action of secondary load and the influence on the track structure are calculated. Moreover, the finite element analysis software ANSYS 18.0 is used to establish the analysis model of the construction of the superstructure of the applied depot. The results show that the influence of the pile foundation settlement produces a certain additional influence on the surrounding tracks, and the maximum value locates at the center of the bearing platform and gradually decreases outward. Under the conditions of informative construction, uniform loading of the structure and control of the construction process, local bias loads and uneven settlements are avoided. The impact of the construction on the track can be effectively controlled, and the impact on the structure can be kept within the allowable limits. By comparing this instance with a number of similar superstructure projects in Beijing, this study shows that the overall risk of this type of project can be controlled and can provide a technical reference for similar superstructure projects on top of a metro depot construction in the future.

A novel formulation for transfer path identification and vibration prediction in the over-track building induced by trains.

Over-track buildings in metro depots become more and more prevalent in metropolis with the increase in population and the decrease of construction land. However, the train-induced vibration greatly reduces the comfort of occupants living in the over-track buildings. Owing to complex vibration sources and numerous transfer paths, it is a challenging task to analyze and predict the vibration characteristics accurately in the building. In this paper, a field measurement campaign of vibration was conducted in the Guanhu metro depot in Guangzhou, China. A novel formulation based on the operational transfer path analysis (OTPA) and singular value decomposition (SVD) is proposed to analyze the measured data and predict the train-induced vibration in the building. In this study, the vibration contributions from each transfer path to the target points in the building were obtained and the predominant transfer paths were identified further. Besides, the vibration at target points in the building was predicted using the vibration at path points and transmissibility functions from transfer paths. This study provides insights into the prediction and evaluation of vibration transmissions from vibration source to upper floors of over-track building.

Resilience-based seismic design of inter-story isolated multi-towers built on large chassis

Multi-towers built on top of a metro depot (a large chassis) have become an important trend in transit-oriented development. Inter-story isolation technology is widely used in high-seismic regions to ensure seismic resilience of such buildings. This study focused on resilience-based seismic designs for such buildings. A typical inter-story isolated two-towers built on a large chassis was selected as the study case, based on a statistical survey. Fifteen cases were designed considering different yield ratios of isolation system and stiffness ratios of the upper towers and large chassis. The influence of these two critical design parameters on the seismic responses and resilience was investigated. The seismic responses and components affecting resilient performance were identified. Based on the analytical results, a resilience-based conceptual design method using the recommended value of critical design parameters was recommended. The reliability and high efficiency of this method were verified through a trial design of four inter-story isolated towers built on a large chassis.

A prediction method for indoor vibration over metro depot throat area based on coupled interactions of wheel-rail

Environmental vibration pollution is the primary environmental problem faced by the superstructure of metro depots. The throat area is especially prone to high wheel-rail impact vibration due to multiple joints and turnouts, which may cause high annoyance to the residents in the superstructures both on the upper cover and surrounding areas. In this paper, based on the coupled dynamic analysis of wheel-turnout, a prediction method to evaluate the indoor vibration of over-track building is established. Firstly, subway turnout with variable sections on switch, connection part and frog and vehicle models are established, and wheel-rail force is obtained through multibody dynamics calculation. Secondly, the track-foundation-structure finite element numerical model was built, loading the wheel-rail force excitation, then the indoor vibration could be obtained. The accuracy of this method is verified taking a 32 story residential superstructure in North China as an example. The vertical vibration accelerations were measured on every other floor when a A-type train travelled on a 7-turnout. The error between the measured data and the calculated results was within 5%, indicating that this prediction method has certain accuracy. The research results have certain guiding significance for the prediction and control of vibration in metro depot.

Experimental study on the maximum temperature under the ceiling in a metro depot with one end closed

Metro systems have been widely developed in many countries all over the world, and its operation safety and environmental control are the key issues need to be investigated, especially for the cases of a fire scenario. In this work, a 1/10th scaled subway tunnel with one end closed was constructed to study the ceiling temperature profiles in the metro tunnel when a fire occurs, and the temperature prediction model was proposed. The heat release rates (13 kW-19 kW) and tunnel slopes (0 %-3 %) were changed, and the horizontal temperature in both the longitudinal and transverse direction under the metro tunnel ceiling were measured. The results showed that the temperature distribution in the longitudinal direction were divided into three stages. The dimensionless temperature rise decreases exponentially with the distance from the plume impingement point, and the attenuation rate increases with the tunnel slope. The maximum temperature of the lateral corresponds to the location at the longitudinal centerline of the tunnel, and the temperature decreases from the highest value and presents a symmetrical distribution. Through dimensional analysis, three prediction models were constructed to forecast the temperature under the ceiling at each stage for different HRRs (heat release rates) and tunnel slopes, and the predicted models were verified by the experimental data, and showed good agreements.