地震作用对轻轨铁路车桥系统耦合振动的影响

本文分析地震作用对考虑土-结构相互作用的轻轨铁路车桥系统耦合振动的影响。文中建立了车桥系统考虑土-结构相互作用的三维空间模型，推导了考虑地震作用车桥系统的耦合振动方程，并编制了相应的计算程序。以时速100km的列车通过天津轻轨的一座四跨预应力混凝土连续刚构桥为例，对受天津波和El Centro波地震作用的车桥系统的耦合振动响应进行了仿真分析。结果表明：地震作用下车桥系统的耦合振动响应近似为桥梁地震响应与车桥系统耦合振动响应之和；地震作用对车桥系统横桥向耦合振动响应的影响最大，对竖向耦合振动响应的影响较小，而对顺桥向耦合振动响应的影响甚微；且不同地震波激励的影响程度有所不同。由此得出结论，地震作用与车桥系统的耦合振动存在很大程度的耦合，因此，在对高架桥梁上的轻轨铁路进行车桥耦合振动分析时必须考虑地震作用的影响，以保证列车运行的安全性和稳定性。     

Prediction of high-speed train induced ground vibration based on train-track-ground system model

The development of analysis on train-induced ground vibration is briefly summarized. A train-track-ground integrated dynamic model is introduced in the paper to predict the ground vibration induced by high-speed trains. Representative dynamic responses of the train-track-ground system predicted by the model are presented. Some major results measured from two field tests on the ground vibration induced by two high-speed trains are reported. Numerical prediction with the proposed train-track-ground model is validated by the high-speed train running experiments. Research results show that the wheel/rail dynamic interaction caused by track irregularities has a significant influence on the ground acceleration and little influence on the ground displacement. The main frequencies of the ground vibration induced by high-speed trains are usually below 80 Hz. Compared with the ballasted track, the ballastless track structure can produce much larger train-induced ground vibration at frequencies above 40 Hz. The vertical ground vibration is much larger than the lateral and longitudinal components.     

Behavior of ground vibrations induced by trains moving on embankments with rail roughness

This study investigates the behavior of ground vibrations induced by trains moving on embankments using theoretical formulations, finite element analyses, and field experiments. The train-induced vibrations are large at the dominant frequencies of nV/L_c, even though the rail is very rough, where n is a positive integer, V is the train speed, and L_c is the carriage interval. For subsonic train speeds, the train-induced ground vibration is extremely small when the rail is perfectly smooth, but with a minor rail irregularity, the train-induced ground vibration can be significantly increased. However, for supersonic train speeds, the ground vibrations with or without rail irregularities are not very different, and the vibration of the first dominant frequency having the longest wavelength is the most obvious wave.     

Study of the train-induced vibration impact on a historic Bell Tower above two spatially overlapping metro lines

There is concern regarding the long-term vibration effects caused by metro trains on historic buildings. In this paper, the impact of metro train-induced vibrations on the Bell Tower in Xi’an above two spatially overlapping tunnels was studied.Metro Line 2 has been operational since 2011, and Line 6 is still under construction. To study and control the effect of micro vibrations on the Bell Tower, a metro train–track–tunnel–soil 3D dynamic FE model was developed. The vibration response generated by Line 2 was then predicted, and the influences of train speed on ground vibration were analysed. In addition, a detailed in situ measurement, which helped calibrate the numerical model and determine the dynamic behaviour of timber structures, was performed. Finally, the calibrated models and measured results were used to predict vibrations caused by road traffic and trains from two spatially overlapping metro lines. This was performed under different route schemes and train operation conditions.The results showed that installing steel spring floating slab tracks (FST) and decreasing train speeds had obvious effects on controlling the ground peak particle velocity (PPV). Simulated results from both the input impulse and output response generated by metro Line 2 matched well with actual measurements. If correct designs are employed, it is possible to resolve the vibration problem on historic buildings caused by metro trains.     

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。     

Experimental investigation of railway train-induced vibrations of surrounding ground and a nearby multi-story building

In this paper, a field experiment was carried out to study train-induced environmental vibrations. During the field experiment, velocity responses were measured at different locations of a six-story masonry structure near the Beijing-Guangzhou Railway and along a small road adjacent to the building. The results show that the velocity response levels of the environmental ground and the building floors increase with train speed, and attenuate with the distance to the railway track. Heavier freight trains indu...     

轨道附近地面振动模型中的饱和地层动力格林函数

列车引起场地振动的建模需要能够表达地层的动力格林函数.本文兼顾饱和土的流固两相耦合性、场地土的分层性和波动的三维传播性,构建了半解析的场地动力格林函数.首先,基于Biot方程,在傅里叶变换域求解固体骨架和流体的位移和应力.然后采用传递矩阵方法建立地表位移和应力间的关系,得到格林函数矩阵.进而讨论矩阵的一些固有特征,提出改善竖向位移计算效率的措施.最后利用推导的格林函数计算了几个典型算例.数值结果与文献中其他方法得到的结果十分接近,与场地振动的现场观测试验基本符合.软土场地振动的计算结果高于饱和砂土场地,高速列车场地振动强度高于低速列车.当车速接近场地瑞利波速,模拟结果中显示出马赫锥.数值结果还显示,即使车速略低于瑞利波速,马赫锥也可能出现.本文推导的格林函数将有助于深入理解列车等移动激励作用下层状饱和土场地的振动特征.     

Shinkansen high-speed train induced ground vibrations in view of viaduct–ground interaction

Train viaduct behavior and nearby ground motion under the high-speed train passage have been studied in this paper. First, the findings from the field measurement alongside the high-speed Shinkansen railway in Japan are interpreted. Then, the computer simulation is made based on the soil-foundation-viaduct interaction analysis under moving axle loads. The solution method is to apply the dynamic substructure method in the frequency domain. The viaduct girders including track structure and pier supports are modeled by the three-dimensional beam-column elements. The supporting pile foundation and nearby field are discretized by the axisymmetric three-dimensional finite elements and analyzed in a semi-analytical way, with a transmitting boundary replacing the far field based on the thin layer element method. Nearby ground motion during train passage on a viaduct have been calculated by superimposing the effects from neighboring pile foundations.The main parameters affecting viaduct vibrations are discussed by taking environmental vibration into consideration. The nearby ground motion along the viaduct is recomputed by applying the above determined forces to the foundation tops. The results from numerical studies are compared with the field test data, thus proving the present simulation to be effective and reliable.     

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。     

Earthquake-induced pounding between equal height multi-storey buildings considering soil-structure interaction

The present paper investigates the coupled effect of the supporting soil flexibility and pounding between neighbouring, insufficiently separated equal height buildings under earthquake excitation. Two adjacent three-storey structures, modelled as inelastic lumped mass systems with different structural characteristics, have been considered in the study. The models have been excited using a suit of ground motions with different peak ground accelerations and recorded at different soil types. A nonlinear viscoelastic pounding force model has been employed in order to effectively capture impact forces during collisions. Spring-dashpot elements have been incorporated to simulate the horizontal and rotational movements of the supporting soil. The results of the numerical simulations, in the form of the structural nonlinear responses as well as the time-histories of energy dissipated during pounding-involved vibrations, are presented in the paper. In addition, the variation in storeys peak responses and peak dissipated energies for different gap sizes are also shown and comparisons are made with the results obtained for colliding buildings with fixed-base supports. Observations regarding the incorporation of the soil-structure interaction and its effect on the responses obtained are discussed. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of equal height buildings during earthquakes, especially the response of the lighter and more flexible structure. It has been found that the soil flexibility decreases storey peak displacements, peak impact forces and peak energies dissipated during vibrations, whereas it usually leads to the increases in the peak accelerations at each storey level.     

3D viscous-spring artificial boundary in time domain

After a brief review of studies on artificial boundaries in dynamic soil-structure interaction, a three-dimensional viscous-spring artificial boundary （VSAB） in the time domain is developed in this paper. First, the 3D VSAB equations in the normal and tangential directions are derived based on the elastic wave motion theory. Secondly, a numerical simulation technique of wave motion equations along with the VSAB condition in the time domain is studied. Finally, numerical examples of some classical elastic wave motion problems are presented and the results are compared with the associated theoretical solutions, demonstrating that high precision and adequate stability can be achieved by using the proposed 3D VSAB. The proposed 3D VSAB can be conveniently incorporated in the general finite element program, which is commonly used to study dynamic soil-structure interaction problems.     

Seismic response of offshore structures in random seas

A study of the dynamic response of offshore structures to simultaneous loadings by random earthquake ground motions and random sea waves is presented. Emphasis is placed on the evaluation of dynamic soil-structure interaction effects and also on the evaluation of non-linear hydrodynamic damping effects due to sea waves for the seismic response. The structure is discretized using the finite element method. Sea waves are represented by Bretschneider's power spectrum and the Morison equation defines the wave forcing function. The Tajimi-Kanai power spectrum is used for the horizontal ground acceleration due to earthquakes. The governing equations of motion are obtained by the substructure method. Response analysis is carried out using the frequency-domain random vibration approach. It is found that the first few vibrational modes contribute significantly to the dynamic response. The response due to earthquake loadings is larger when the soil-structure interaction effects are considered. The hydrodynamic damping forces are higher in random seas than in still water and sea waves reduce the seismic response of offshore structures. Studies on the first passage probabilities of response indicate that small sea waves enhance the reliability of offshore structures against earthquake forces.     

Numerical prediction of low-frequency ground vibrations induced by high-speed trains at Ledsgaard, Sweden

The ground vibrations induced by a passenger train at the test site of Ledsgaard, Sweden, have been analysed and numerically simulated through a spectral element discretization of the soil. To calculate the spatial distribution of loading due to train passage, the train is decoupled from the track, and a suitable series of static forces is applied. The track and the embankment are modeled as a beam on elastic foundation, using analytical solutions for loads moving at constant velocity. The results of both 2D and 3D modelling assumptions are thoroughly discussed, in terms of prediction of track motion and of attenuation of peak ground velocity with distance.     

极限安全地震动下考虑土-结构相互作用的核电站安全壳响应分析

根据黏弹性人工边界的基本原理,结合有限元分析软件ABAQUS和MATLAB辅助程序,在地基有限区域上添加黏弹性人工边界并实现极限安全地震动的输入。基于ABAQUS软件平台,对CPR1000安全壳构建了土-结构相互作用体系的数值模拟模型,分析其在极限地震动下的动力响应,并将计算结果与考虑刚性基础的安全壳结构响应数据进行对比。结果表明:核电站CPR1000安全壳结构在极限安全地震动下仍能保持良好的密闭性。考虑土-结构相互作用后分析所得安全壳结构受到的应力、加速度峰值和相对位移均有所增大,使用刚性地基模型要偏于危险。     

Prediction of railway ground vibrations: Accuracy of a coupled lumped mass model for representing the track/soil interaction

Recent advances in railway-induced ground vibrations showed that the track/soil interaction plays an important role in the low frequency range. This paper contributes to the numerical analysis of train/track/foundation dynamics by presenting the accuracy of a coupled lumped mass (CLM) model devoted to the railway foundations and to the track/soil coupling. Following a summary of the background and the advantages of the CLM model, the coupling strategy is quantified through two application cases. Firstly, the dynamic track deflection is calculated for different railway lines considering various degrees of complexities of foundations. Then, the foundation responses are compared depending on whether detailed coupling is introduced or not. The benefit of the proposed model is emphasized by presenting free-field ground vibration responses generated by a tram and a high-speed train, obtained by a revisited two-step prediction model developed by the authors.     

Propagation and attenuation characteristics of various ground vibrations

In order to effectively control vibration related problems, the development of a reliable vibration monitoring system and the proper assessment of attenuation characteristics of various vibrations are essential. Various ground vibrations caused by train loading, blasting, friction pile driving and hydraulic hammer compaction were measured using 3D geophones inside of the borehole as well as on the ground surface, and the propagation and attenuation characteristics of various source generated vibrations were investigated by analyzing particle motions. For the geometric modeling of various vibrations, the types of various sources and their induced waves were characterized and the geometric damping coefficients were determined. The measured attenuation data matched well with the predicted data when using the suggested geometric damping coefficient, and the estimated soil damping ratios were quite reasonable taking soil type of the site and experiencing strain level into consideration.     

Numerical analysis on seismic response of Shinkansen bridge-train interaction system under moderate earthquakes

This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.     

Contact stresses and ground motion generated by soil-structure interaction

A study has been made of the dynamic contact stresses that the foundation of a nine-storey reinforced concrete building exerts on the soil during forced vibration tests. The effects of the flexibility of the foundation on the contact stress distribution and on the force-displacement relationship for the foundation have been examined in an attempt at testing several simplifying assumptions commonly used in soil-structure interaction studies. Comparisons of calculated and observed ground displacements induced by soil-structure interaction in the immediate neighbourhood of the building have also been presented.     

考虑土与结构相互作用效应的结构减震控制大型振动台模型试验研究

本文设计并完成了考虑土与结构相互作用的结构减震控制大型振动台模型试验。通过对四种结构形式的对比试验，探讨了土与结构相互作用（ＳＳＩ）效应对结构地震反应的影响以及调谐质量阻尼器（ＴＭＤ）在刚性和柔性地基条件下对主体结构的减震效应。通过比较同一地震动作用下主体结构在刚性和柔性两种地基条件下的地震反应，可知：ＳＳＩ效应具有降低和提高结构减震控制效果的双重作用，其综合效果与输入地震动的频谱特性、加速度峰值大小有关。由于ＳＳＩ效应在结构地震反应中发挥着双重的作用，因而使得基于刚性地基假定下设计的ＴＭＤ减震控制系统在柔性地基条件下的控制效果不太理想，甚至会出现负面效应。本文还探讨了在柔性地基条件下影响结构减震控制效果的一些因素。