Papers by Author: Rong Chen

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Authors: Rong Chen, Wang Ping
Abstract: Based on principle of vehicle-track-bridge dynamic interaction, a dynamic simulation model of a high-speed electric multiple units (EMUs) passing over turnout on bridge was established. The calculation focused on 200km/h No.12 improved ballasted turnout (60kg/m rail) being laid on 3×32.0m simply supported beam, it analyze dynamic characteristics of a freight train with 25t axle load passing at speed of 120km/h and those of CRH1 EMUs passing at speed of 200km/h. Results show that: when the freight train passes the turnout through the main line, the vertical stiffness of the simply supported beams is not sufficient due to the relatively high speed and large axle load; when the EMUs passes the turnout on bridge, the dynamic deflection change rates of girders at the switch and frog are great and the turnout is not appropriately set on the bridge, so the frog crosses over the beam gap, which results in the increasing of track irregularity and finally causes derailment coefficient of vehicle to overrun to reduce the running safety; when a train passes the turnout zone on bridge, interaction between the vehicle and turnout is significant because of load fluctuation of the wheel caused by inevitable structural irregularity at the switch and nose rail, and this requires strengthening measurement and running within speed limit.
Authors: Rong Chen, Wang Ping, Shun Xi Quan
Abstract: In order to study dynamic behavior of vehicle-turnout-bridge coupling system, a vehicle-turnout-bridge dynamic analysis model is established by employing the dynamic finite element method (FEM). When No.18 crossover turnouts(with a speed of 350km/h) are laid symmetrically on the 6×32m continuous beam, influences of turnout/bridge relative position and wheel/rail contact relation in turnout zone on the system dynamic responses are analyzed. The result shows that: wheel/rail contact of turnout zone (especially the frog) has great effect on dynamic responses of turnout on bridge, thus the nose rail height of frog should be optimized to mitigate the wheel load transition and its longitudinal gradient. In terms of the 32m-span continuous beam, the best relative position is frog part of turnout arranged in the range of 1/8 and 1/4 of span.
Authors: Rong Chen, Wang Ping, Xian Kui Wei
Abstract: Railway turnout, an integrated mechatronics equipment of track technology, is one of key equipments that control the running speed of high-speed railway. During the conversion of turnout, the friction, inclusion of foreign matter and deficient displacement of conversion caused by its own structural characteristics may lead to severe wheel/rail impact. In order to study the influence of conversion deviation on safety and comfort of a train during passing the turnout, train/turnout dynamic model was applied. Taking No.18 turnout on a Passenger Dedicated Line (PDL) with 350km/h as a case study, when the train passed it, the influences of its deficient displacement and inclusion of foreign matter on the following dynamic responses were studied, i.e. wheel load distribution, wheel flange force, dynamic stress of rail, wheel unloading rate, derailment coefficient, as well as the lateral displacements of switch rail and nose rail, etc. Result shows that: (1) the deficient displacement and the inclusion of foreign matter will severely influence the normal operation of the turnout, so the safety and comfort during the train passing through turnout may be affected; (2) During the conversion of turnout, its deficient displacement should be controlled properly, and the foreign matter should be removed during routine maintenance, moreover, a reliable detection system should be set.
Authors: Rong Chen, Wang Ping, Hao Xu
Abstract: A high degree of integrity is the most remarkable feature that makes double-block ballastless track different from other ballastless track structure. Based on the beam/plate theory on elastic foundation, influences of several structural parameters (such as size of track slab and support layer, support stiffness of the subgrade, etc) on stress of the ballastless track system under the axle load of 300kN were studied in order to obtain further understanding of the mechanic performance of double-block ballastless track under the train load. Results show that: structure of double-layer combined structure should be adopted to decrease the stress of each layer of ballastless track; the width of support layer should be less than 3.6m; because the ratio of track slab stress to support layer stress is larger than the ratio of their strength, the width of track slab in the double-layer separated structure should be 280mm or less.
Authors: Rong Chen, Wang Ping, Zhe Liu
Abstract: CA mortar is a key component of slab track. It is used as the material for leveling damping structure layer between the rigid track slab and concrete trackbed of slab track in high speed rail. In order to determine functions of CA mortar with low elastic modulus (EM), the beam/plate theory on elastic foundation was applied to the calculation of slab track’s stress. Under the bonding or no-bonding condition, the influence of CA mortar’s EM on the warping stress and displacement of track slab were calculated. Stress distribution of CA mortar under the common effects of train load and temperature gradient was explored, and the intensity requirement of CA mortar with different EM was put forward. Calculation results show that longitudinal and lateral bending moments of base plate both increase with the increasing of CA mortar’s EM; when the CA mortar’s EM is in the range of 50~10000MPa, there is gap between track slab and the mortar and the deformation of CA mortar (50mm thick) is not enough to compensate the warpage of the track slab; with the increasing of CA mortar’s EM, the tensile and compressive stresses of CA mortar both increase under the common effects of train load and temperature gradient, thus higher requirements on tensile and compressive strength are demanded when CA with high elastic modulus is used.
Authors: Rong Chen, Wang Ping, Bin Wang
Abstract: Based on turnout/bridge interaction principle and finite element method (FEM), an integrated turnout/beam/pier model of jointless turnout on ballasted track was established to analyze the influences of expansion joint on stress and deformation of the turnout. The results are concluded as follows: whether the rail expansion joint is set in front of or behind the turnout, expansion additional force of stock rail will be reduced greatly at the end of the beam; so do the expansion displacement of switch rail and nose rail, the stress of displacement restrictor and spacer block, rail break gap and the longitudinal force of one rail after the other rail broke. But when the expansion joint is set in front of the turnout, the pier’s longitudinal force of continuous beam bridge and the simply supported beam bridge (within the expansion range of the device) increase greatly. When the device is close to the turnout, longitudinal relative displacement of the stock rail to the girder also increases a lot. By comparison, it is more favorable to set the expansion joint behind the turnout, or to set the device at the both ends of the continuous beam, or to set the device at the ends of continuous beam rather than in the center of the span.
Authors: Rong Chen, Wang Ping, Wei Hua Zhao
Abstract: According to mechanical characteristics of welded turnout on continuous-slab-track and bridge, an integrated turnout/track slab/beam/pier finite element model was established to analyze the interaction between welded turnouts on continuous-slab-track and bridge. The study focused on No.18 turnout (60kg/m rail) with movable frog being laid on a (32+48+32) m continuous beam, expansion additional force and braking additional force of the turnout were calculated when the temperature dropped. The results show that the longitudinal interaction between welded turnouts on continuous-slab-track and bridge is small, which presents a reasonable structure type of welded turnout on bridge; in calculation of the expansion force, when the temperature drops, the shrinkage and creep of the base-slab and longitudinal stiffness reduction caused by the cracking are considered, so the results are more representative than those from the case of rising temperature. Therefore, the case of temperature dropping should be the main concern in design; under the action of the braking force, stress and deformation of each component within this turnout/bridge system are comparatively large.
Authors: Rong Chen, Wang Ping, Yang Song
Abstract: Train/turnout dynamic interaction is exacerbated by high speed of passenger train and heavy load of freight train, and wheel/rail relation is one of the key factors that determine the running characteristics of the train. Focusing on three types of wheel treads with different profiles (TB tapered tread, LM worn tread, LMA worn tread), longitudinal distribution of the contact geometric parameters along the switch rail and nose rail of 350km/h No.18 turnout are calculated, such as tread equivalent conicity, coefficient of contact angle difference, roll angle factor, gravitational stiffness of wheelset, gravitational angle stiffness of wheelset, etc. Results show that: (1) LMA worn tread produces the smallest irregularity; (2) wheel/rail vertical impact at the frog will become bigger; (3) Top profile of switch rail and nose rail should be designed according to the wheel tread type so as to mitigate the wheel/rail dynamic interaction and increase the safety and stability of a train.
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