地铁车站结构截面控制内力计算分析

目前，在地铁车站结构设计中，一般采用将荷载满布到结构模型进行内力分析，并未考虑不同活载布置对结构内力的影响，从而导致部分截面设计存在安全隐患。文章以成都地铁3号线一期工程红牌楼南站结构模型为例，运用MIDASGEN有限元分析软件对不同活载布置下结构的内力进行比较，得出地铁车站各截面控制内力所对应的活载布置，为地铁车站结构设计提供借鉴。     

Simulation of dynamic interaction between train and railway turnout

Dynamic train–track interaction is more complex in railway turnouts (switches and crossings) than that in ordinary tangent or curved tracks. Multiple contacts between wheel and rail are common, and severe impact loads with broad frequency contents are induced, when nominal wheel–rail contact conditions are disturbed because of the continuous variation in rail profiles and the discontinuities in the crossing panel. The absence of transition curves at the entry and exit of the turnout, and the cant deficiency, leads to large wheel–rail contact forces and passenger discomfort when the train is switching into the turnout track. Two alternative multibody system (MBS) models of dynamic interaction between train and a standard turnout design are developed. The first model is derived using a commercial MBS software. The second model is based on a multibody dynamics formulation, which may account for the structural flexibility of train and track components (based on finite element models and coordinate reduction methods). The variation in rail profile is accounted for by sampling the cross-section of each rail at several positions along the turnout. Contact between the back of the wheel flange and the check rail, when the wheelset is steered through the crossing, is considered. Good agreement in results from the two models is observed when the track model is taken as rigid.     

Mathematical modelling of train–turnout interaction

The paper proposes a mathematical model of train–turnout interaction in the mid-frequency range (0–500 Hz). The model accounts for the effects of rail profile variation along the track and of local variation of track flexibility. The proposed approach is able to represent the condition of one wheel being simultaneously in contact with more than one rail, allowing the accurate prediction of the effect of wheels being transferred from one rail to another when passing over the switch toe and the crossing nose. Comprehensive results of train–turnout interaction during the negotiation of the main and the branch lines are presented, including the effect of wear of wheel/rail profiles and presence of track misalignment. In the final part of the paper, comparisons are performed between the results of numerical simulations and line measurements performed on two different turnouts for urban railway lines, showing a good agreement between experimental and numerical results.     

盾构隧道始发与到达段环间纵向压力空间分布规律研究

现场实测数据表明，盾构隧道始发与到达段各断面纵向压力较小，可能导致环缝漏水。为解决此问题，通过求解描述隧道变形特征的微分方程，获得隧道始发与到达段纵向力的分布规律；并以此为依据，提出纵向拉结构件的设计方法。研究结果表明： 1)在不采用拉结措施的情况下，进出洞口附近纵向力最小，接近于0； 2)距离洞口越远的断面，其纵向力越大； 3)采用纵向拉结措施可以有效地增大始发与到达段断面纵向力。在对纵向拉结构件进行设计时，其最小横截面积由隧道刚度和环缝止水垫闭合压力决定，其最小长度由隧道和地层之间的切向黏结刚度决定。     

盾构隧道管片结构纵向错台研究

盾构隧道通缝拼装管片结构的错台一直是困扰盾构隧道施工的技术问题，且由错台引起的管片开裂、拼装困难和防水隐患等问题对施工和运营的影响日益凸显，并直接影响到工程质量。以上海轨道交通二号线西延伸段盾构隧道工程为背景，采用现场监测和数值计算方法对盾构推进过程中管片错台进行分析，获得了管片结构错台发生及发展的变化规律。进一步探讨了盾构千斤顶的顶力对错台大小及发展规律的影响，为盾构施工中减小错台，提高施工精度和质量，以及盾构隧道设计施工提供依据。     

Numerical simulation of wave-induced nonlinear motions of a two-dimensional floating body by the moving particle semi-implicit method

The moving particle semi-implicit (MPS) method was applied to compute nonlinear motions of a floating body influenced by the water on deck. To compute the motions of a rigid body, the fluid pressure at the position of each particle on the body surface was directly integrated in space and the equations of translational and rotational motions were integrated in time to determine the correct position of the rigid-body surface at each time step of the time-domain calculation. The performance of this method was validated through a comparison with measured results in an experiment that was newly conducted using a model of a box-shaped floating body with a small freeboard. Although the overall agreement was good, some discrepancies were observed for a shorter wave period, especially for the drift motion in sway. The effect of numerical resolution on the results was checked by changing the number of particles. With a higher number of particles, no obvious improvement was seen in the global body motions, but the resolution of the local free-surface profile, including the water on deck, was improved.     

(48+80+48)m连续梁桥与轨道系统地震响应规律研究

为研究高速铁路连续梁桥-轨道系统地震响应规律,采用非线性弹簧模拟线路纵向阻力,建立考虑轨道及下部结构的(48+80+48)m连续梁桥-轨道系统仿真模型,分析温度、活载和制动作用下桥上无缝线路梁轨相互作用纵向力分布规律,在此基础上,研究地震作用下连续梁桥-轨道系统动力响应特性。研究表明:温度、活载及列车制动作用下梁轨相对位移、钢轨应力等均在桥台附近取得极大值,地震频谱特性对梁轨系统动力响应有很大的影响。     

Design of Nonlinear Controllers for Active Vehicle Suspensions Using Parameter-Varying Control Synthesis

Nonlinear suspension controllers have the potential to achieve superior performance compared to their linear counterparts. A nonlinear controller can focus on maximizing passenger comfort when the suspension deflection is small compared to its structural limit. As the deflection limit is approached, the controller can shift focus to prevent the suspension deflection from exceeding this limit. This results in superior ride quality over the range of road surfaces, as well as reduced wear of suspension components. This paper presents a novel approach to the design of such nonlinear controllers, based on linear parameter-varying control techniques. Parameter-dependent weighting functions are used to design active suspensions that stiffen as the suspension limits are reached. The controllers use only suspension deflection as a feedback signal. The proposed framework easily extends to the more general case where all the three main performance metrics, i.e., passenger comfort, suspension travel and road holding are considered, and to the design of road adaptive suspensions.     

Theoretical and experimental excitation force spectra for railway-induced ground vibration: vehicle–track–soil interaction,irregularities and soil measurements

Excitation force spectra are necessary for a realistic prediction of railway-induced ground vibration. The excitation forces cause the ground vibration and they are themselves a result of irregularities passed by the train. The methods of the related analyses – the wavenumber integration for the wave propagation in homogeneous or layered soils, the combined finite-element boundary-element method for the vehicle–track–soil interaction – have already been presented and are the base for the advanced topic of this contribution. This contribution determines excitation force spectra of railway traffic by two completely different methods. The forward analysis starts with vehicle, track and soil irregularities, which are taken from literature and axle-box measurements, calculates the vehicle–track interaction and gets theoretical force spectra as the result. The second method is a backward analysis from the measured ground vibration of railway traffic. A calculated or measured transfer function of the soil is used to determine the excitation force spectrum of the train. A number of measurements of different soils and different trains with different speeds are analysed in that way. Forward and backward analysis yield the same approximate force spectra with values around 1 kN for each axle and third of octave.     

城市轨道交通上跨铁路特大桥方案研究

武汉轨道交通7号线北延线工程上跨铁路桥需跨越多股铁路，受天河机场限高等因素影响，主桥设计为（86+2×156+86）m预应力连续梁桥。设计中通过增加梁高、调整预应力钢束布置减少梁体残余徐变变形，采用二次张拉竖向钢绞线预应力体系改善主梁腹板抗裂性能。为减小施工对既有铁路的干扰，采用转体施工方案，转体吨位达15 000 t。邻近铁路的基坑采用隔离桩支护，基坑开挖和桥梁施工各阶段既有铁路路基附加沉降均满足规范要求。