Numerical analysis of dynamic response of vehicle–bridge coupled system on long-span continuous girder bridge

To systematically study the vehicle-bridge coupled dynamic response and its change rule with different parameters, a vehicle model with seven degrees of freedom was built and the total potential energy of vehicle space vibration system was deduced. Considering the stimulation of road roughness, the dynamic response equation of vehicle-bridge coupled system was established in accordance with the elastic system principle of total potential energy with stationary value and the ＂set-in-right-position＂ rule. On the basis of the self-compiled Fortran program and bridge engineering, the dynamic response of long- span continuous girder bridge under vehicle load was studied. This study also included the calculation of vehicle impact coefficient, evaluation of vibration comfort, and analysis of dynamic response parameters. Results show the impact coefficient changes with lane number and is larger than the value calculated by the ＂general code for design of highway bridges and culverts （China）＂. The Dieckmann index of bridge vibration is also related to lane number, and the vibration comfort evaluation is good in normal conditions. The relevant conclusions from parametric analyses have practical significance to dynamic design and daily operation of long-span continuous girder bridges in expressways. Safety and comfort are expected to improve significantly with further control of the vibration of vehicle-bridge system.

Seismic response analysis of road vehicle-bridge system for continuous rigid frame bridges with high piers

The objective of this study is to investigate the effects of earthquakes on road vehicle-bridge coupling vibration systems. A two-axle highway freight vehicle is treated as a 13 degree-of-freedom system composed of several rigid bodies, which are connected by a series of springs and dampers. The framework of the earthquake-vehicle-bridge dynamic analysis system is then established using an earthquake as the extemal excitation. The equivalent lateral contact force serves as the judgment criteria for sideslip accidents according to reliability theory. The entire process of the vehicle crossing the bridge is considered for a very high pier continuous rigid frame bridge. The response characteristics of the vehicle and the bridge are discussed in terms of various parameters such as earthquake ground motion, PGA value of the earthquake, incident angle, pier height, vehicle speed and mass. It is found that seismic excitation is the most influential factor in the responses of the vehicle-bridge system and that the safety of vehicles crossing the bridge is seriously impacted by the dual excitations of earthquake and bridge vibration.

COUPLING VIBRATION OF VEHICLE-BRIDGE SYSTEM

By applying the sinusoidal wave mode to simulate the rugged surface of bridge deck,accounting for vehicle-bridge interaction and using Euler-Bernoulli beam theory, a coupling vibration model of vehicle-bridge system was developed. The model was solved by mode analyzing method and Runge-Kutta method, and the dynamic response and the resonance curve of the bridge were obtained. It is found that there are two resonance regions, one represents the main resonance while the other the minor resonance, in the resonance curve. The influence due to the rugged surface, the vibration mode of bridge, and the interaction between vehicle and bridge on vibration of the system were discussed. Numerical results show that the influence due to these parameters is so significant that the effect of roughness of the bridge deck and the mode shape of the bridge can't be ignored and the vehicle velocity should be kept away from the critical speed of the vehicle.

Natural Frequency of the Bridge—Vehicle Coupled System Considering Uniform Distributed Moving Load

Natural frequencies of the bridge—vehicle coupling system considering uniform distributed load varying with position is investigated in this work.An analytic model of a simply supported beam bridge with constant section is introduced to establish the frequency equations of the coupled system.Comparisons with the results between analytic model and FEM indicate that the present research is correct and reasonable.In view of an example bridge,natural frequencies are studied on the bridge subjected to uniform distributed moving loads in cases of different weight and span,by which some regular phenomenon are obtained.The present study can apply in the engineering problem of interaction between bridges and moving loads such as trains and tracked vehicles.

A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

Purpose–This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approach–The track and substructure are decomposed into the rail subsystem and substructure subsystem,in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener.The rail is treated as a continuous beam with elastic discrete point supports,and spring-damping elements are used to simulate the constraints between rail and fastener.Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system,while the external load is used to deal with the reverse effect.The fastener failure is simulated with the methods that cancel the forced vibration transmission,namely take no account of the substructure–rail interaction at that position.Findings–The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method.Local fastener failure will slightly affect the vibration of substructure and carbody,but it will significantly intensify the vibration response between wheel and rail.The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value,respectively,under the train speed of 350 km$h
1.At the same time,the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%,respectively,from the normal value.Originality/value–This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

Impact coefficient and reliability of mid-span continuous beam bridge under action of extra heavy vehicle with low speed

To analyze the dynamic response and reliability of a continuous beam bridge under the action of an extra heavy vehicle, a vehicle–bridge coupled vibration model was established based on the virtual work principle and vehicle–bridge displacement compatibility equation, which can accurately simulate the dynamic characteristics of the vehicle and bridge. Results show that deck roughness has an important function in the effect of the vehicle on the bridge. When an extra heavy vehicle passes through the continuous beam bridge at a low speed of 5 km/h, the impact coefficient reaches a high value, which should not be disregarded in bridge safety assessments. Considering that no specific law exists between the impact coefficient and vehicle speed, vehicle speed should not be unduly limited and deck roughness repairing should be paid considerable attention. Deck roughness has a significant influence on the reliability index, which decreases as deck roughness increases. For the continuous beam bridge in this work, the reliability index of each control section is greater than the minimum reliability index. No reinforcement measures are required for over-sized transport.

Dynamic performance analysis of a seismically isolated bridge under braking force

In order to study the dynamic performance of seismically isolated bridges under the most unfavorable loads in the longitudinal direction, a dynamic equation for vehicle braking in the longitudinal direction is established. A four or five- order Runge-Kutta method is adopted to obtain the time-history response of a wheel set under braking force. The quadratic discretization method is then used to transform this time-history into a braking and bending force time-history of a structural fixed node, and a dynamic response analysis of the seismically isolated bridge under the vehicle＇s braking force is carried out using ANSYS, a universal finite element analysis software. According to the results, seismic isolation design results in a more rational distribution of braking force among piers; the influence of the initial braking velocity on the vehicle braking force is negligible; the location where the first wheel set leaves the bridge is the most unfavorable parking location; a seismic isolation bridge bearing constructed according to typical design methods enters into a yield stage under the braking force, while the shearing force at the bottom of the pier declines as the isolation period is extended; the design requirements can be met when the yield displacement of the seismic isolation bearing is less than 5 mm and the yield strength is greater than the braking force.

Dynamic Characteristics of Metro Vehicle under Thermal Deformation of Long-Span Cable-Stayed Bridge

In order to study the influence of thermal deformation of long-span cable- stayed bridge (LSCSB) on the dynamic characteristics of metro vehicle on the bridge, based on the theory of vehicle-track coupled dynamics, the rigid-flexible coupled dynamic model of metro vehicle-track-LSCSB system is established by using finite element method and multi-rigid-body dynamics. Adopting this model, the deformation of LSCSB subject to temperature is analyzed, then the comprehensive effect of track random irregularity and rail deformation caused by temperature load is considered to study the dynamic characteristics of metro vehicle running through the bridge, and finally the influences of temperature increment and running speed on concerned dynamic indices of vehicle are studied. The results show that the LSCSB deforms obviously subject to temperature load, and the overall performance is that the cooling is arched, and the heating is bent, and the shape variable changes almost linearly with the temperature load. According to the parameters studied in this paper, the rail deformation caused by temperature load increases the wheel-rail vertical force, derailment coefficient and wheel load reduction rate by 1.5%, 3.1% and 5% respectively. The vertical acceleration of the vehicle body decreases by 2.4% under the cooling condition, while increases by 3.7% under the heating condition. The dynamic response of the bridge changes under temperature load. The maximum vertical and horizontal displacement in the middle of the main beam span are 6.24 mm and 2.19 mm respectively, and the maximum vertical and horizontal acceleration are 1.29 cm/s2 and 2.54cm/s2 respectively. The derailment coefficient and vertical acceleration of vehicle body are more affected by temperature load, and the wheel load reduction rate and wheel-rail vertical force are more affected by speed. The conclusion of this paper provides a reference for subsequent scholars to study the influence of thermal deformation on the dynamic response of vehicles on LSCSB.

基于等效刚度阻尼系统的中低速磁浮列车与大跨度桥梁耦合振动响应分析

针对中低速磁浮列车与大跨度连续梁桥的耦合动力响应问题,本文基于等效刚度阻尼系统建立多编组磁浮列车模型;基于国内在建磁浮专线连续梁桥(35m+55m+35m),采用ANSYS中实体单元建立全桥模型.并将两个独立系统在SIMPACK进行车桥耦合,设定车重参数分别为空载、定员和超载,且列车按单线和双线工况运行,计算耦合系统的动力响应.结果表明,本文建立的列车模型受到轨道激励时,磁浮间隙在额定范围内浮动,即等效刚度阻尼系统有良好的控制效果;车辆磁浮间隙的变化量、车体竖向加速度与车重成反比,而磁浮力与车重成正比;在计算工况下,桥梁主跨及边跨的竖向位移均满足设计要求的限值,双线列车超载运行桥梁跨中最大位移仅为4.503mm.说明连续梁桥具有较大的刚度,能满足磁浮车辆安全运行的要求;对比列车单双线运行,主跨跨中的竖向位移最大值后者达到前者两倍,而边跨位移的最大值后者仅比前者增大70%,表明双线列车对开运行对桥梁的动力响应存在增大效应.相关研究成果对磁浮线路建设有一定参考意义.

温度作用下大跨度斜拉桥长波不平顺限值研究

研究目的:为研究大跨度斜拉桥在温度作用下的变形及其引起的长波不平顺对列车运行的影响,以泉州湾跨海钢混结合梁斜拉桥为研究对象,在其主梁截面布置温度传感器以监测主梁温度变化,利用ANSYS软件分析实测温度作用下的斜拉桥主梁竖向变形,将温度变形与轨道不平顺叠加且基于弹性系统动力学总势能不变值原理建立考虑该长波不平顺的车桥耦合模型,以研究长波不平顺对列车动力响应的影响、弦测法对其进行评价的适配性,以及温度变形极限条件下的对应限值。研究结论:(1)温度监测系统共收集了1年的温度数据,将其分解为均匀温度和线性温差后,对应的温度变化范围分别为[5.82°C,37.51°C]和[2.36°C,29.94°C],主梁主跨跨中的最大竖向位移为28.6 mm,最小竖向位移为14.1 mm;(2)相比于未考虑温度作用,考虑了温度作用引起的长波不平顺的车桥耦合振动模型得到的列车轮重减载率、竖向加速度和竖向舒适度指标均有一定增大,竖向加速度增幅最为明显;(3)考虑了因列车运行引起的桥梁动态位移的影响后,60 m弦中点弦测法依然能够很好地体现列车振动响应,与车体竖向加速度响应相关性最好;(4)通过分析60 m弦的不平顺计算结果并进行验证,可知桥塔附近是双线行车时会车的危险位置;(5)在温度变形极限条件下列车的竖向加速度达到规范限值,对应的60 m弦矢度限值为7.22 mm;(6)本研究成果可为大跨度斜拉桥长波不平顺的评测方法选取及限值要求提供参考。

车桥耦合连续梁-拱组合桥冲击系数研究

为了得到连续梁-拱组合桥真实的冲击系数,以某三跨连续梁-钢管混凝土拱组合桥为依托,考虑车桥耦合振动效应,利用ANSYS建立大桥空间梁单元模型和车辆的三轴半车模型,分析桥面不平度、车速、车辆数对主梁不同部位及不同响应冲击系数的影响,并以车速和桥面不平度为自变量得到冲击系数二元回归公式,最后利用2座基频相近桥梁冲击系数的实测数据验证该公式。结果表明:桥面不平度对冲击系数影响最大,当桥面不平度达到B级以上,冲击系数超过规范值,最大可达规范值5.42倍;对于主梁,不同外部激励、不同响应和不同部位的冲击系数存在差异,部分冲击系数超出规范值;该文给出的冲击系数回归公式可用于类似结构主梁冲击系数估算。

参数冻结精细指数积分法在非线性车桥耦合振动分析中的应用

描述车桥耦合作用的基本问题是一个时变系统问题,且很多工况下需考虑非线性特性,使得该问题难以得到解析解,甚至数值解也可能很复杂.针对该问题的求解,提出了一种参数冻结精细指数积分法,将其应用于车桥耦合动力学模型的数值分析中.该方法结合了精细积分和指数积分特点,并将时变系数矩阵在每一积分步参数冻结,用于获得系统振动响应的数值解.考虑汽车轮胎与桥面的力和位移耦合关系、桥面沥青铺装层、桥梁材料黏弹性和几何非线性特性,建立了车桥耦合动力学模型,并应用参数冻结精细指数积分法对该模型进行了求解.通过与近似解析解、辛Runge-Kutta算法以及经典的Newmark-β数值积分法计算结果进行对比,验证了所提出方法计算结果的有效性和准确性.在此基础上,制作了缩尺车桥耦合系统模型,测试了跨中挠度响应,进一步验证了理论建模和所提算法的有效性和实用性.通过数值计算分析了所提算法的数值特性,结果表明:提出的参数冻结精细指数积分法不仅可以处理时变、非线性问题,且具有良好的数值计算精度和长时间数值稳定性;由于精细积分的特点,参数冻结精细指数积分法的计算时间步长可以取的较大,可有效提高计算效率.因此,所提出的参数冻结精细指数积分法预期可成为求解车桥耦合动力学问题的一种新的高效算法.

CRTSⅢ型板和双块式无砟轨道振动噪声特性研究

【目的】探究高速铁路CRTSⅢ型板和双块式无砟轨道的结构振动与噪声特性。【方法】以有限元、多体动力学与边界元相结合的方法为基础,通过建立高速列车-无砟轨道-箱梁耦合动力学模型和边界元模型,研究列车高速通过时的列车-轨道-箱梁耦合系统的结构动力响应,以及噪声辐射特性。【结果】结果表明,列车通过桥上CRTSⅢ型板与双块式轨道结构段时,列车的最大轮重减载率分别为0.0536与0.1657,下部箱梁挠度分别为1/9673与1/8457。与双块式无砟轨道相比,CRTSⅢ型板的轨道板及底座位移响应更小,并且轨道-箱梁系统的竖向振动衰减更快,减振性能更优。另外,比较两种轨道结构条件下的高架箱梁结构噪声,CRTSⅢ型板段的箱梁噪声总声压级更小。但是,桥下远场点噪声峰值差异较小,峰值频率接近,均为31.5Hz左右;而桥下峰值频率差异较大,Ⅲ型板的峰值频率为63Hz,双块式则为20Hz。【结论】CRTSⅢ型板式无砟轨道更适合在高速铁路桥梁段使用。

悬挂胶轮列车与钢桥的振动试验及仿真研究

为评价悬挂胶轮列车及钢轨道梁桥的结构性能,以开封悬挂式单轨示范线为背景开展现场试验与仿真研究。开发了胶轮列车-钢轨道梁桥耦合振动分析程序,根据现场实测的胶轮车辆的空气弹簧、走行轮刚度和阻尼等力学参数,建立胶轮列车模型。对车桥动力响应的现场试验与动力仿真分析结果进行综合比较,采用相关规范对列车走行性以及轨道梁桥的动力性能进行综合评估。结果表明:车桥动力特性及其振动响应的理论与实测结果基本吻合,车桥耦合分析方法可应用于悬挂式胶轮单轨交通系统振动性能研究;轨道梁竖向挠跨比小于相关规范的限值,竖向刚度设计合理;在列车竖向静活载作用下,相邻两跨轨道梁梁端竖、横向转角之和最大值分别为4.5‰和1.5‰;车速80 km/h下轨道梁纵、横向应力动力系数最大值分别为1.17和1.14;考虑到悬挂式胶轮列车没有脱轨风险,列车轮重减载率及钢轨道梁桥横向加速度较传统铁路偏大,其相应限值可较现行铁路规范适当放松。

车流密集程度对重载随机车流与桥梁耦合振动影响分析

目的 将元胞自动机建立的重载随机车流模型引入车桥耦合振动系统,探究重载随机车流密集程度激发桥梁振动响应规律。方法 基于元胞自动机和NaSch模型,模拟道路交通周期边界条件下单向双车道重载随机车流,真实还原桥梁上车流演变规律,建立考虑车型、车速、车道、车重和驾驶员行为特性的重载随机车流-桥梁耦合振动模型;采用MATLAB软件编程求解重载随机车流与桥梁耦合振动特性。结果 重载车流从自由流向阻塞流转变,桥梁竖向挠曲变形逐渐增大,振动加速度先增大后减小;阻塞流时桥梁产生最大竖向变形,密集流时桥梁竖向振动速度和加速度响应最剧烈。桥梁振动响应的能量峰值主要集中在桥梁主频4 Hz和9 Hz附近,且随着车流密度增大、车速降低,随机车流激发的桥梁振动响应能量峰值先增大后减小。结论 车辆占有率为18%的密集流出现最大振动响应能量峰值,车辆占有率为31%的拥挤流最易激发桥梁高阶频率振动。

预应力效应对中速磁浮线路简支梁车-桥耦合振动响应的影响

以长沙磁浮线路简支梁桥为研究对象,建立考虑不同预应力效应的磁浮线路简支梁桥车-桥耦合振动模型,分析预应力效应对中速磁浮线路车-桥耦合振动响应的影响。结果表明:预应力效应的变化对桥梁动力响应影响明显,预应力增加显著加剧桥梁竖向振动加速度,预应力由0.67P0(P0为张拉控制应力)增加到1.33P0时,桥梁跨中竖向最大加速度从0.21 m/s^(2)增至0.44 m/s^(2);车速增加会加剧预应力效应的影响,对桥梁竖向振动加速度的影响尤为明显,车速由20 km/h增加到200 km/h时,在1.00P0作用下,桥梁跨中竖向最大加速度从0.15 m/s^(2)增至0.76 m/s^(2);箱壁局部变形对车-桥耦合竖向振动响应有显著影响,预应力导致的箱壁局部变形不可忽略。

桥梁刚度变化对高速铁路独塔斜拉桥车⁃桥耦合振动的影响分析

以高速铁路独塔斜拉桥为研究对象,建立车-轨-桥耦合系统的空间多体动力学分析模型,开展高速铁路斜拉桥的车-轨-桥耦合振动的仿真分析。通过改变材料弹性模量的方式调整桥塔和主梁刚度,研究桥梁刚度变化对桥梁车-桥-耦合振动的影响规律。研究结果表明,随着桥塔刚度的增大,主梁跨中竖向和塔顶纵向位移响应逐渐减小,其峰值减幅分别为7.57%和10%;随着主梁刚度的减小,主梁跨中竖向位移和塔顶纵向位移峰值呈逐渐递增趋势,主梁刚度变化对车体竖向加速度和Sperling竖向舒适度指标影响相对较大;相比于桥塔刚度的变化,主梁刚度变化对车-桥振动响应的影响更大;整体上,列车运行的安全性和平稳性指标满足规范要求。

考虑冲刷效应的大跨桥梁地震-风-车-桥耦合振动分析

为研究冲刷效应对地震与风联合作用下大跨桥梁动力响应的影响,在已建立的地震-风-车-桥耦合振动分析模型基础上,利用p-y曲线(p为土阻力,y为变形)折减法考虑不同冲刷深度的桩土荷载-位移关系,根据桩土荷载-位移关系和冲刷深度更新桩基的侧向支撑刚度和长度,从而考虑了冲刷效应对大跨桥梁动力响应的影响,并将模型应用到江顺大桥冲刷效应的分析研究中.研究结果表明:基础冲刷减弱了地基土对结构的侧向约束,从而降低结构的自振频率,侧向振型的自振频率最大降低6.01%;在运营车辆和风荷载作用下,基础冲刷对结构的振动响应影响很小;在地震发生后,基础冲刷会增大结构的横向振动,结构的横向位移响应极值最大增大9.1%,横向位移响应谱也相应增大,而对结构的竖向振动影响很小;基础冲刷可能减小车辆横向加速度的响应,车辆的横向加速度响应极值最大降低7.7%,对车辆的竖向振动影响很小.

大件运输车作用下宽幅斜拉桥动力响应分析

为研究大件运输车辆作用下桥梁的动力响应,建立了以实际工程为背景的宽幅斜拉桥有限元模型和精细化的车辆有限元模型,并利用LS-DYNA程序的接触算法实现了相较于传统方法更为真实的车-桥耦合振动模拟,以车辆类型、行驶车道、行驶速度等为参数,对比不同工况下桥梁的振动响应。结果表明:在大件运输车辆通过宽幅斜拉桥时,相较于标准车辆会引起桥梁更大的竖向下挠和拉索索力;边车道工况下桥梁的竖向位移变幅和索力变幅大于中间车道工况下的变幅;大件运输车辆行驶速度的提升会使桥梁竖向下挠和拉索索力增加,且相较于中间车道工况,边车道工况下桥梁响应对车速的敏感度更高。

基于ANSYS的简支梁车-桥-支座耦合动力响应分析

为准确模拟车辆过桥产生的振动,应考虑支座弹性作用的影响。结合分离法与汽车动力学原理,分别建立车辆、桥梁和支座的计算模型并通过位移协调关系和力的平衡关系进行车-桥-支座耦合。基于ANSYS中APDL语言,以30 m简支箱梁桥为算例研究桥面不平整度、支座刚度和阻尼对车-桥-支座耦合动力响应的影响。结果表明,桥面平整度越差,车辆行驶过程中对桥梁产生的冲击力越大,激发桥梁的动力响应越剧烈;适当增大支座刚度能有效降低桥梁动挠度,减弱振动响应;支座阻尼具有耗能作用,增大支座阻尼对削弱桥梁加速度响应有明显的效果;在设计桥梁支座时,应适当增大支座刚度和阻尼来削弱车-桥-支座耦合振动对桥梁的冲击作用。