Dynamic Train Loads Research Articles

Alignment control for a long span urban rail-transit cable-stayed bridge considering dynamic train loads

In this paper, bridge alignment control with considering dynamic train loads was experimentally and theoretically investigated. Analytical process of bridge dynamics and the self-adaptive Kalman filter bridge alignment control method with considering the dynamic train loads were briefly introduced. The static measurement, the dynamic test, the field alignment measurement as well as the finite element analysis (FEA) of the second longest rail transit cable-stayed bridge in the world were carried out. Based on the results, the train dynamic load effect on the bridge alignment was obtained quantitatively. Subsequently, alignment control of the rail transit bridge with considering this effect using a self-adaptive Kalman filter method was analyzed. The results show that: (a) the dynamic train loads have effects on alignment control of the bridge and therefore cannot be neglected; (b) the self-adaptive Kalman filter method is applicable and reliable for alignment control of bridges during construction. The analytical method and whole process contribute to develop a related specification and further engineering applications.

실대형 실험을 통한 아스팔트 노반상 자갈궤도의 거동 특성

아스팔트 노반상 자갈궤도(이하, AC자갈궤도)는 아스팔트 콘크리트 노반(이하, AC노반)에 의한 열차하중의 분산으로 노반 두께 감소 효과, 빗물의 침투방지 효과로 인한 노반부의 강도저하와 연약화 방지 효과, 노반 분니 방지 및 동상방지에 의한 유지보수비 절감 효과를 얻을 수 있다. 이와 같은 장점들에 의해 AC자갈궤도는 유럽 및 일본 등에서 널리 사용되고 있으며 국내에서도 도입을 위한 연구가 진행 중이다. 본 논문에서는 유한요소해석 프로그램인 ABAQUS을 이용하여 현재 철도설계기준에 제시되어 있는 고속철도용 자갈궤도의 성능에 부합하는 AC자갈궤도 단면을 선정하고 선정된 2개의 단면을 대상으로 실물 대형 정 동적 열차하중 재하 시험을 수행하였다. 실대형 실험 결과, AC자갈궤도가 강화노반 상면에 작용하는 토압이 상대적으로 작게 측정되었으며 탄성 및 소성변위도 상대적으로 유사 또는 작은 것을 알 수 있었다. 따라서 AC자갈궤도가 자갈궤도에 비해 열차하중 분산효과에 의한 강화노반 두께 감소효과가 있고 소성변위도 작으므로 궤도의 장기 유지관리 측면에서도 유리한 궤도구조임을 확인하였다. Ballasted track on an asphalt roadbed can be beneficial for its various effects such as (i) decreasing of roadbed thickness by dispersing train load; (ii) prevention of both strength reduction and weakening in roadbed system by preventing rainwater penetration; and (iii) reducing maintenance cost by preventing roadbed mud-pumping and frostbite. With these beneficial effects, ballasted track on asphalt roadbed has been widely used in Europe and Japan, and relevant research for applying such ballasted track on asphalt roadbed systems in Korea is ongoing. In this study, full-scale static and dynamic train load tests were performed to compare the performance of ballasted track on asphalt roadbed and ballasted track. The optimum thickness levels of asphalt and reinforced roadbeds, corresponding to the design criteria for reinforced roadbed of high-speed railway, was estimated using the FEM program ABAQUS. Test results show that the earth pressure on reinforced roadbed of ballasted track on the asphalt roadbed was relatively low compared with that of simple ballasted track. The elastic and plastic displacements of simple ballasted track on the asphalt roadbed were also lower than those of ballasted track. These test results may indicate that the use of ballasted track on asphalt roadbed is an advantageous system in view of long-term maintenance.

Matching experimental and numerical data of dynamic power train loads by modeling of defects

AbstractDefects on wind turbines such as power train misalignments or blade pitch angle deviations are dealt with. These defects cause additional dynamic excitations and thus can reduce the fatigue life of wind turbine components.In order to improve the reliability of dynamic load computations and related fatigue dimensioning of wind turbines, a highly discretized simulation model that incorporates potential system defects is set up. A sensitivity analysis of the impact of system defects on power train dynamics is performed. Experimental measurements of gearbox orbital paths and of the corresponding torque arm loads could be reproduced with good correlation when the simulation model was complemented by power train misalignments and by blade pitch angle deviations. Comparisons of experimental and numerical data are presented in time and frequency domains. Feasible consequences about the impact of alignment defects on the resulting fatigue damage are presented. Copyright © 2014 John Wiley & Sons, Ltd.

Simulation Study on Train-Induced Vibration Control of a Long-Span Steel Truss Girder Bridge by Tuned Mass Dampers

Train-induced vibration of steel truss bridges is one of the key issues in bridge engineering. This paper talks about the application of tuned mass damper (TMD) on the vibration control of a steel truss bridge subjected to dynamic train loads. The Nanjing Yangtze River Bridge (NYRB) is taken as the research object and a recorded typical train load is included in this study. With dynamic finite element (FE) method, the real-time dynamic responses of NYRB are analyzed based on a simplified train-bridge time-varying system. Thereinto, two cases including single train moving at one side and two trains moving oppositely are specifically investigated. According to the dynamic characteristics and dynamic responses of NYRB, the fourth vertical bending mode is selected as the control target and the parameter sensitivity analysis on vibration control efficiency with TMD is conducted. Using the first-order optimization method, the optimal parameters of TMD are then acquired with the control efficiency of TMD, the static displacement of Midspan, expenditure of TMDs, and manufacture difficulty of the damper considered. Results obtained in this study can provide references for the vibration control of steel truss bridges.

열차이동하중 작용시 구조물 접속부의 동적 거동특성 연구

This paper systematically analyzes the dynamic effects of structure approaches which are expected to have direct effects on train loads - according to the train`s acceleration as the area under consideration is located in a section where acceleration of high speed railway vehicles and the train`s operating speed happens. In addition, through an examination of the dynamic train loads, dynamic behavioral characteristics of embedded structures and structure approaches were analyzed and a numerical analysis has been carried out in order to evaluate the performance of track subgrade and the safety of the structure. As a result, we reach the conclusion that the dynamic effects by train loads is low, but somewhat high vertical acceleration occurs.

Analysis of Whole Weathered Granite Improved Soil Subgrade Dynamic Response

In this paper, strain and displacement for FLAC3D numerical simulation analysis of the whole weathering granite improved soil subgrade in train dynamic load of the stress is conducted, subgrade under repeated load test data and software simulation data is contrasted, the center of subgrade vertical settlement and the center of the subgrade stress change situation is researched.Through the research proves the whole weathering improved soil subgrade can ensure the high-speed safety, comfort and use requirement.

Analysis on Vibrations due to High-Speed Railway Tunnel and Control Measures

With the economy developing rapidly, China has entered the era of high-speed railway, but at the same time, the negative impact of high-speed railway is increasing obviously. The paper analyzes the induced environmental vibration problems due to the high-speed railway, the specific response in the power of the shield tunnel under the train loads, the tunnel structure and the surrounding strata, When the local layer is saturated sand, by calculating the pore water pressure and the layer stress, determining whether it can cause sand liquefaction phenomenon or not, judging the damage extent of tunnel structure, especially it may influences the normal operation of the train. The vertical displacement of the tunnel structure due to the dynamic train load may have impact on the normal operation of the train, where some preventive measures should be taken, such as concrete grouting reinforcement method. In this paper the non-reinforcement case is compared to the reinforcing ones, and different reinforcement ring thickness is studied in order to determine a reasonable thickness of the reinforcement. The main contents include the following work: （1）Response analysis by using the FLAC3D software to simulate the shield tunnel under the dynamic train loads which are the main cause of the displacement of the segment and surrounding strata. The simulation study mainly includes analysis of the changes of pore water pressure and stress. （2） Since train load can produce the vertical displacement, prevention and controlling measures should be taken, which mainly use grouting reinforcement.

열차 하중 작용 시 블록식 보강토 옹벽으로 지지된 철도 노반의 거동

Static and dynamic train load tests were conducted to evaluate the train load transfer mechanism in the roadbed which was retained by two types (fully and partially) of segmental retaining walls reinforced by geogrid. The test roadbed was 2.6m high, 5m wide, and 6m long. A combination of earth pressure gages, displacement transducers, and strain gages were placed in specific locations to measure the responses. Test results showed that the wall displacement pattern as well as the earth pressure for the fully reinforced retaining wall was different from those for the partially reinforced retaining wall. In the dynamic train load test, the strain in the upper part of the wall tended to decrease, and both the residual deformation and the rate of the deformation were significantly lower than those in the current design standard.

Probabilistic Analysis of Ground Surface Vibration Due to Train Movement, a Case Study on Tehran Metro Line 4

Ground surface vibration produced by moving train is one of the most important aspects in urban areas. The purpose of this study is the probabilistic analysis of ground surface vibration, which is generated by metro transportations. For this reason, Tehran metro line 4 is considered as a case study. In this paper, at first, a new procedure is used to simulate train dynamic load. In the second step, based on the variation of geomechanical properties and train characteristics in Tehran metro line 4, more than 60 numerical models are simulated. The results of numerical simulations are analyzed by multivariate statistical technique and an equation for prediction of peak particle velocity (PPV) in the ground surface is presented. In the next step, probabilistic analysis is done using Monte Carlo Simulation (MCS). Finally, sensitivity of input data on ground surface vibration is discussed and the impact of geomechanical properties and train characteristics on the surface vibration is considered. Based on the probabilistic analysis, PPV in the surface region of Tehran metro line 4 is <2.76 mm/s with 95 % probability.

The Experimental Study on Engineering Characteristics of Improved Clay

The rapid transit railway foundation bed bears the repeated dynamic load of train besides the static-load from upper structure. The engineering characteristics of improved clay, in especial the dynamic performance under repeated dynamic load or train, is the key factors to determine the improved clay can be used as roadbed fill material. In this paper, the dynamic triaxial test is adopted to imitate the repeated load of train, and the engineering characteristics of improved clay is studied such as dynamic stress plastic strain and elastic strain etc. which influence the running seriously.

Numerical analysis of ground surface vibration induced by underground train movement

The purpose of this study is the simulation of train movement and calculation of ground surface vibration induced by train movement in the subway tunnel. Tehran metro line 4 that is located in a populated area was considered as a case study. For simulation of train movement, effective factors on dynamic load magnitude and frequency have been studied and variation of wagon force in a longitude model is considered. Then Fourier amplitude spectrum was computed by means of Fast Fourier Transformation (FFT) of the dynamic train load and then the frequency range of train load was determined. In the next step, low energy frequencies were filtered and the dynamic load as a point load was applied on the numerical model of the tunnel and the ground surface vibration was determined. Finally, the result of the numerical model is verified by Metrikine and Vrouwenvelder’s analytical model. Comparisons of numerical and analytical solutions shows that the numerical results have a good agreement with the analytical output and the maximum displacement in the horizontal and vertical directions are 3.75 and 5.25mm, respectively.

Dynamic Testing of Corrugated Steel Plate Culvert Using Radar

The paper presents the results of selected experimental tests under dynamic loads that were conducted on a corrugated steel plate culvert. The tested railway object in the cross section has two spans in shape of closed arch. The effective length of shells is L1 = L2 = 4400 mm. The dynamic loads were caused by the passages of various trains. The displacements and vibration frequencies of the culvert were determined. The microwave interferometric radar was used for monitoring of displacements of this railway culvert. The maximum displacements of the culvert crown do not exceed 0.65 × 10 -3 m. The typical frequencies of the railway culvert to passing trains were usually in the range of 0.6 to 3.0 Hz. They were obtained during passage of the heavy freight trains. Conclusions drawn from the tests can be helpful in the measurements of such culverts using the microwave interferometry method. The dynamic and static tests of bridges and culverts are conducted in order to confirm structural specifications, or to provide diagnostic surveys for planning maintenance and modernization. Typical experimental tests are usually carried out using accelerometers, strain and inductive (or dial) gauges. These gauges are quite accurate and reliable. Moreover, testing of structures can give rise to accessibility problems, often requiring the use of scaffolds. For these reasons, the application of radar measurements is a quite good alternative. The interferometric radar applied in tests, is a precision microwave instrument suitable to the non-contact vibrations and displacements monitoring of various engineering structures. The high accuracy and quickness of measurement are among of the main characteristic features of the radar. The comparison of the interferometric radar vs. the accelerometer used for dynamic monitoring of various large bridges is given by Pieraccini et al. (1) and Gentile and Bernardini (2). The interferometry method for non-contact dynamic and static measurement of the vibration of various engineering structures was described by Dei et al. (3), Gentile (4), Fratini et al. (5). The main aim of this paper is the evaluation of possibility of the interferometric radar application for the measurements of corrugated steel plate (CSP) culvert under dynamic train loads. The vertical displacements and vibration frequencies were determined during the field load tests. The

Multimodel LQ controller design for variable-speed and variable pitch wind turbines at high wind speeds

This paper focuses on designing a multimodel linear quadratic (LQ) controller for variable-speed horizontal axis wind turbines. Those turbines use blade-pitch and electromagnetic torque control to meet specified objectives for three regions of operation. We aim in this paper to use the blade-pitch control in the high wind speed operating zone. The controller is then designed in order to optimise a trade-off between two main control objectives which are alleviation of drive train dynamic loads and maximisation of energy efficiency. It is thereafter implemented for a deloaded operation to provide an additional operating reserve necessary to increase the effective participation of the wind turbines in the system frequency regulation. A 2MW wind turbine is considered to illustrate the good performances brought by the proposed approach by presenting and discussing the simulation results.

Vibration simulation of a multi-story high-speed railway station

Station is an important building in high-speed railway, and its vibration and noise may significantly affect the comfort of waiting passengers. A coupling vibration model for train-structure system is established to analyze and evaluate the vibration level of a typical waiting hall under dynamic train load. The motion of a four-axle vehicle with two suspension system is modeled in multi-body dynamics with linear springs and dampers employed. The station is modeled as a whole finite element structure which is 113 m in longitudinal and 163.5 m in lateral, and the stiffness of the station foundation is considered. According to the assumptions that both wheel and rail are rigid bodies and keep contact to each other in vertical direction, and the wheel/rail interaction and displacement coordination in horizontal direction is defined by the simplified Kalker creep theory, the vehicle spatial vibration model has 27 degrees-of-freedom. An overall analysis procedure is made of the train moving through the station, by which the dynamic responses of the train and the station are calculated. According to the comparison between analysis and test results, the actual connection status between different parts of the station is estimated and the vibration level of the waiting hall is evaluated.

전기철도 급전시스템의 순시전압강하 보상을 위한 단상 배전 STATCOM의 적용

AC 전기철도 시스템은 동적 단상부하가 빠르게 변화하고, 전철 급전변전소에서 3상 전력을 단상 전력으로 변환한다. 이것은 일반 배전 시스템과 비교해서 AC 전기철도 시스템의 전기적인 현상들이 다르다는 것을 나타낸다. AC전기철도 열차부하의 전기적인 특성은 동적부하의 운영과 운행 스케쥴, 트랙의 구배 등에 따라 연속적인 변화를 받고 있다. 이와 같은 열차부하의 운영에 따른 급전거리가 길어 전압강하, 전압 불평형 및 고조파 왜곡현상 등의 전력품질 저하요인이 발생하게 된다. 이러한 문제점은 상위계통인 송전시스템의 안정도에 악영향을 줄뿐만 아니라, 전기철도 급전시스템의 전력품질 저하, 전기철도차량의 통신장비, 운행 및 수송량 제한에도 영향을 미치게 된다. 따라서 본 논문에서는 전기철도시스템의 과도상태 평가를 위해 PSCAD/EMTDC를 이용한 평가모델을 제시하고, 전압 강하에 주안점을 두어, 전기철도 급전시스템의 말단 분기점(Sectioning Post)에 정지형 무효전력 보상장치인 단상 배전 STATCOM(Single-phase Static Synchronous Compensator)을 설치하여 그 작용에 따른 전압강하 보상을 평가하였다.

Ground vibration due to railway traffic—The calculation of the effects of moving static loads and their experimental verification

The propagation of waves through homogeneous or layered soil is calculated based on half-space theory. The moving dynamic loads of a train are approximated by fixed dynamic loads and the wave field can be calculated if the spectrum of the dynamic train loads is known. In addition to this dynamic wave field, there are three different components at three different frequency ranges which are caused by the passage of the static loads: • the regular static component at low frequencies, • the irregular static component at medium frequencies, • the sleeper-passing component at high frequencies. For each of these components, an approximate solution is presented. The calculated wave field is compared with measurements of different trains at different sites. The measurement of impulse and harmonic point load excitation verifies the soil dynamic base of the method.