大跨度简支钢桁梁桥车-桥耦合振动影响因素分析

以黄韩侯铁路新黄河特大桥156m简支钢桁梁桥作为工程背景,建立车辆动力模型、桥梁有限元模型并考虑轮轨关系,以蛇形运动和轨道不平顺作为系统的自激激励源,利用大型有限元软件ANSYS以及UM(Universal Mechanism)动力学分析软件联合进行仿真分析。从桥梁结构的桥门架、宽跨比、曲线钢桁梁桥和车辆系统的轨道不平顺以及货车编组角度出发,研究大跨度简支钢桁梁桥车-桥耦合振动的影响因素。经过计算分析得出:钢桁梁桥桥门架对桥梁跨中加速度影响较大;曲线钢桁梁桥随着线路半径的增大,各车辆动力响应参数逐渐变小,轮轨力受到影响;钢桁梁桥宽跨比的增加使得横向刚度随之增加,桥梁横向振动变小;各项车辆动力响应均随着轨道情况变差而总体呈现逐渐增大趋势,车辆安全性、舒适性和平稳性指标逐渐变差;全列空车编组和空重混编对钢桁梁车-桥耦合系统是不利的编组形式,实际情况中应该避免。     

铁路大跨度简支钢桁梁桥车-桥耦合振动研究

桥梁作为线路工程中不可或缺的重要枢纽,对列车通过桥梁时,桥梁和车辆之间相互作用的问题迫切需要做出解答,特别是针对铁路钢桁梁,并考虑大跨度简支特性的车-桥耦合振动问题研究更具有一定的理论与实际意义。以黄韩侯铁路新黄河特大桥156 m简支钢桁梁桥作为工程背景,建立车辆动力模型、桥梁有限元模型并考虑轮轨关系,以蛇形运动和轨道不平顺作为系统的自激激励源,利用大型有限元软件ANSYS以及UM(Universal Mechanism)动力学分析软件联合进行仿真分析,实现单个机车、编组客车和编组货车以设计时速通过桥梁时对大跨度简支钢桁梁桥车-桥耦合振动的研究。经过计算分析得出:大跨度钢桁梁桥的横向刚度相对较小;不同编组情况以设计时速通过桥梁时,车辆和桥梁的各项动力响应参数均在规范允许的范围之内;编组货车通过桥梁时,桥梁跨中横向、竖向加速度较之其他编组情况要大。     

高速铁路车-桥耦合体系地震响应分析及报警阈值研究

高铁是国民经济大动脉的重要组成部分,运输业的生力军。"十二五"规划中将铁路运输安全放在十分重要的位置,并明确提出"大规模发展具有运能大、安全舒适、全天候运输、环境友好和可持续性等优势的高速铁路"的重要目标。由于我国地震频发,地震灾害对我国的高铁网络构成了严重的威胁,而目前我国高速铁路线路中桥梁所占的比例已经超过了50%,地震发生时列车运行在桥上的概率增大,因此,考虑车-桥耦合作用的高铁列车地震安全性评价和地震报警阈值研究有待于进一步加以推进。我国高铁地震报警和紧急处置系统的研究和示范工程建设才刚刚起步,目前系统尚未得到真实地震的检验,经验积累较少,所采用的一些技术参数,如报警阈值等的合理性有待于进一步研究论证,需要解决的一些关键问题有:(1)合理的车-桥耦合模型的构建;(2)车-桥耦合体系地震响应的分析;(3)基于中国高速铁路轨道谱的高铁列车地震安全性评价;(4)确定合理的高铁列车地震报警阈值。本文主要针对以上几个关键问题开展研究工作,主要研究内容和成果如下:(1)模型研究。基于现有基础调研资料确定列车模型和桥梁模型具体参数以及车-桥耦合接触关系。通过弹簧和阻尼器建立桥梁与轨道、轨道与列车之间的连接,建立了高铁列车-高架桥耦合有限元模型,通过车-桥耦合动力特性分析验证模型的合理性。轮轨接触力基于空间动态轮轨关系求解:基于非线性赫兹接触理论计算轮轨法向力,基于Kalker线性理论计算轮轨蠕滑力,再通过Hedrick-Elkinss理论对计算结果进行非线性修正。(2)车-桥耦合地震响应分析。选取典型地震动加速度时程作为外部激励,对车-桥耦合体系地震响应进行分析研究,得到车-桥耦合体系桥面加速度响应放大系数,研究地震频谱特性对桥面地震响应的影响规律。同时建立不考虑高铁列车的等跨单桥模型,对其进行地震响应分析,与车-桥耦合模型计算结果进行对比分析。结果表明,车-桥耦合模型与单桥模型动力特性和地震响应存在一定的差异,在高铁桥梁地震响应分析中,考虑车-桥耦合是必要的。(3)高铁列车地震响应分析。以计算得到的车-桥耦合体系桥面加速度时程作为输入,同时分别采用中、德轨道不平顺样本作为内部激励,基于车-轨耦合动力分析理论,对高铁列车地震反应进行计算分析,得到列车的动力响应值,包括列车的脱轨系数、轮重减载率、横向轮轨力等,并对比规范中该三项指标限值,对高铁列车地震安全性进行评价。结果表明,基于中国轨道谱计算得到的地震作用下列车安全性三项指标值与按照德国谱计算得到的结果差异较大,采用德国谱计算得到列车安全性评价三项指标值均大于中国谱,较中国谱偏于保守。(4)高铁列车地震报警阈值研究。选取不同频谱特性的典型地震动记录,通过调整地震动峰值进行大量计算分析,基于高铁列车安全性三项指标求解得到不同车速下允许的地震动强度限值曲线,对全部地震动记录对应的限值曲线进行包络取值,得到最小包络限值曲线,对其进行适当简化,最终给出不同车速下高速铁路列车地震紧急处置系统的报警阈值建议值和简化公式。研究结果表明,考虑高速铁路轨道谱,采用德国谱比中国谱得到的地震报警阈阈值小。由于德国谱目前在国内应用较为广泛和成熟,有必要进一步验证中国高速铁路轨道谱的合理性与可行性,并应用于实际工程。     

地震作用下高速铁路车-线-桥耦合系统动力响应分析

地震激励对高速车辆-简支箱梁桥系统动力响应的影响关系到高速铁路运营安全。基于车辆-轨道耦合动力学和列车-轨道-桥梁动力相互作用理论,运用有限元和多体动力学方法,建立高速铁路桥梁区段车辆-轨道-桥梁耦合系统动力学模型,分析在人工地震波作用下高速铁路车-线-桥耦合系统动力响应。结果表明:地震激励对轨道板、支撑层和桥梁的横向振动特性的影响大于对垂向振动特性的影响,桥梁结构对地震激励的敏感程度大于轨道结构;车辆运行速度对系统垂向振动特性的影响大于对横向振动特性的影响。研究结论可为地震荷载作用下高速铁路安全运营提供理论依据。     

分析土和结构相互作用的一种实用耦合方法

提出一种新的数值解与解析解耦合的理论和计算方法,研究土-结构相互作用(SSI)体系的地震动力响应。采用大型有限元软件OpenSees模拟复杂结构的非线性行为,用等效线弹性频域内解析解模拟地基土的行为,使用时域离散递归方法将频域内的解析解转化到时域内,再通过子结构边界上力和位移的协调条件来求解。二者之间的耦合和实时数据交流通过CS集成方法来实现。以一个单自由度算例和一个实际工程为例,验证此方法的精度、稳定性和工程实用性,对比在考虑和不考虑SSI体系情况下结构动力响应的区别。本文所提的耦合SSI计算方法和部分研究成果可为工程设计人员提供参考。     

大功率井-地电磁同步发射技术分析与系统实现

为了提高勘探深度和分辨率,对于地球物理传统可控源电磁法的人工激励场源而言,主要通过提高其发射功率和更换激发方位的途径来实现,但是单套的发射系统会因为功率的增加而变得笨重、复杂和可靠性降低,且不适用于金属矿复杂的探测环境.本文采用分布于勘探目标区周边多个方位的中功率同步发射系统来组合成一套大功率发射系统,该系统可以显著提高探测区接收信号的信噪比,有望克服传统可控源类方法的探测盲区和获取可靠性更高的异常体反演结果.每个单套发射系统由发电机、开关供电电源、发射电缆、发射电极、发射机及其外控同步激发控制器构成.利用此发射系统可以在地面或井下的多个位置布设多个人工激励场源,同时对异常体进行扫频激发,频率范围覆盖10 kHz~0.01 Hz,单套发射系统的最大发射功率为48 kW,发射电流大于60 A,同时,在地面、井道、巷道或已有的探测井中采集电磁场信号.通过对均匀半空间理论场值的叠加计算以及实际数据的对比研究发现,多方位场源同时激发能够提高目标区信噪比,并初步验证了其可行性.该方法对可控源电磁法系统提出了一种全新的研发方向,为金属矿勘探提供了一种新的探测手段.

     

基础柔性对土-结构相互作用系统响应影响的一个解析解

采用波函数展开法,通过SH波入射均匀半空间中二维埋置半圆形刚柔复合基础-单质点模型,推导土-刚柔复合基础-上部结构动力相互作用的解析解,并验证解的正确性。研究表明:基础柔性对于系统响应峰值与系统频率有较大影响。考虑基础柔性后,上部结构相对响应峰值相比全刚性基础结果均有一定减小,且系统频率也会产生向低频偏移的现象。     

A response spectrum method for random vibration analysis of mdf systems

A response spectrum method for stationary random vibration analysis of linear, multi-degree-of-freedom systems is developed. The method is based on the assumption that the input excitation is a wide-band, stationary Gaussian process and the response is stationary. However, it can also be used as a good approximation for the response to a transient stationary Gaussian input with a duration several times longer than the fundamental period of the system. Various response quantities, including the mean-squares of the response and its time derivative, the response mean frequency, and the cumulative distribution and the mean and variance of the peak response are obtained in terms of the ordinates of the mean response spectrum of the input excitation and the modal properties of the system. The formulation includes the cross-correlation between modal responses, which is shown to be significant for modes with closely spaced natural frequencies. The proposed procedure is demonstrated for an example structure that is subjected to an ensemble of earthquake-induced base excitations. Computed results based on the response spectrum method are in close agreement with simulation results obtained from time-history dynamic analysis. The significance of closely spaced modes and the error associated with a conventional method that neglects the modal correlations are also demonstrated.     

Impact interactions between two vibration systems under random excitation

The exact stationary solutions of the random response of two special vibration systems with impact interactions are formulated in this paper. Between the two systems, the Hertz contact law is used to model the contact process during vibration. A clearance is also introduced. The excitation is assumed to be a stationary white Gaussian process with zero mean and acting on the two systems independently. By assuming the ratio of the excitation and damping parameter of each system to be the same, the exact solutions can be found through solving the time-independent Fokker-Planck equation. The effects of contact stiffness, clearance and the system properties on the response are discussed probabilistically. From this study, it is found that, under some cases, the contact phenomena still play an important role on the response even when the clearance is larger than three times the root mean square response of the corresponding linear systems.     

Fuzzy random vibration of multi-degree-of-freedom hysteretic systems subjected to earthquakes

Earthquake excitation not only has evident randomness but also has strong fuzziness owing to the uncertainties in the definition of earthquake intensity and site soil classification. In this paper, the seismic ground motion is simulated as a stationary filtered white noise with fuzzy parameters, an analytical procedure is proposed to analyse the fuzzy random vibration of multi-degree-of-freedom (MDOF) hysteretic systems, and the covariance matrix of the fuzzy random responses is derived by the equivalent linearization technique. Finally, some numerical results for a two-storey shear hysteretic frame are presented to demonstrate the validity and effectiveness of the procedure proposed.     

Non-linear analysis of coupled wall systems

The non-linear response history and failure mechanism of coupled wall systems under dynamic loads and static loads are investigated through an analytical model. The walls and coupling beams are replaced by flexural elements. Axial and shear stiffnesses are included for the wall members. The stiffness characteristics of each member are determined by inelastic properties. The suitable hysteresis loops to each constituent member are established to include the specific characteristics of coupled wall systems. The computed results are compared with results obtained from tests using model structures statically and dynamically tested on the Illinois Earthquake Simulator.     

Seismic safety assessment with non-Gaussian random processes for train-bridge coupled systems

Extensive high-speed railway(HSR) network resembled the intricate vascular system of the human body,crisscrossing mainlands. Seismic events, known for their unpredictability, pose a significant threat to both trains and bridges,given the HSR’s extended operational duration. Therefore, ensuring the running safety of train-bridge coupled(TBC) system,primarily composed of simply supported beam bridges, is paramount. Traditional methods like the Monte Carlo method fall short in analyzing this intric...     

基于随机振动理论的抗震分析方法研究进展

介绍了随机振动理论在工程结构抗震分析方法中的最新进展。对近年来发展的虚拟激励法在线性结构系统中所具有的高效随机振动分析作了较为完整的介绍,尤其在多点地震激励的随机振动分析中具有优越性。同时,介绍了最新发展的概率密度演化方法,这一方法在非线性结构系统分析中具有独特性,可获得非线性结构反应的概率密度分布及其随时间的变化过程。     

An efficient,adaptive algorithm for large-scale random vibration analysis

An efficient, adaptive and robust algorithm is proposed to reduce the cost of large-scale stationary and transient random vibration analysis of structures excited by multiple partially correlated nodal and or base excitations. The cost saving is accomplished by computing integrals selectively, and yet attempting to maintain a level of accuracy desired by the analyst. Recently, proposed closed-form solutions for fully coherent propagating band-limited white-noise excitation are used to rank approximately the terms in the modal covariance matrix. Terms are then evaluated starting from the most important one, and the computations are terminated in such a way that the accuracy level requested by the user is satisfied in an approximate sense. Two variations of the algorithm are proposed: the first one is more robust and is preferred, and is recommended when computing a relatively small number (hundreds) of response quantities; the second one is more efficient when computing a very large number (thousands) of response quantities. Both variations are adaptive, and consider the closeness, damping and participation of all modes explicitly, while the first method also considers the mode shapes. The efficiency and accuracy of the algorithm is investigated by using it to compute the stationary and transient seismic response of the Golden Gate suspension bridge.     

Application of coupled analysis methods for prediction of blast-induced dominant vibration frequency

Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.     

多点激励下结构随机地震反应分析的反应谱方法

基于随机振动理论,提出了多点激励作用下线性系统随机地震反应分析的均值反应谱方法,给出了结构峰值反应的均值、标准差以及反应平均频率的反应谱组合公式。这可以将反应谱方法推广应用到多点激励结构的抗震可靠度分析中。鉴于组合公式中谱参数和相关系数需要由烦琐的数值积分得到,本文进一步针对它们给出合理的简化计算式,从而使得建议的反应谱方法的计算效率大大增加。最后,以一个双塔斜拉桥为例,对本文方法进行了验证。基于建议方法的计算结果与Monte Carlo模拟结果吻合较好。与经典的多点激励反应谱方法(MSRS法)比较,本文方法具有其无法比拟的计算效率。     

A generalization of the timoshenko beam model for coupled vibration analysis of thin-walled beams

A generalization of the Timoshenko beam model is presented which accounts for the influence of the shear strains, due to non-uniform bending and torsion, on the flexural-torsional vibrations of thin-walled cores with open or closed cross-section. The axial displacement field incorporates the torsion secondary warping as well as the warping terms depending on the shear resultants. It is shown that exact solutions for the interior domain problem can be obtained under proper load conditions. Moreover, a discrete model for the free-vibration analysis is derived by adopting a linear interpolation of the unknown functions and a reduced integration in order to avoid locking phenomena. Various applications are developed, including the case of the coupled vibrations of a shear-core-steel-frame building.