铰接车辆模型识别粗糙桥梁频率和振型的数值分析

根据车桥耦合振动理论和桥梁间接测量法基本原理,对实际工程某连续梁桥建立桥梁模型,采用2辆单轴1/4车辆模型模拟测量车辆,1辆双轴半车模型模拟牵引车辆提供额外桥梁激励,三车前后铰接建立车辆模型。基于分离法原理与车辆动力学理论,利用约束方程实现任意时刻车轮与桥面接触点的位移协调关系,采用APDL编程实现铰接车辆过桥的耦合动力时程响应分析。提取前后测试车辆匀速通过不同等级粗糙桥面时车辆振动加速度时程响应,对通过桥梁同一位置处的前后测试车辆加速度数值进行相减处理并应用快速傅里叶变换识别桥梁频率。采用带通滤波技术与汉宁窗相结合的处理方法提取分离出与桥梁固有频率相关的桥频分量响应,利用桥频分量响应及其希尔伯特变换构造出与每阶固有频率相对应的振型。结果表明:在A、B、C级桥面不平整度条件下,采用铰接车辆模型识别出的桥梁前3阶频率相对误差均在1%以内; 对加速度时程响应数据加窗处理后识别出的桥梁前3阶振型MAC值均在0.95以上,满足工程精度需求; 研究结果可以为移动传感间接测量方法在桥梁检测工程中的应用提供理论参考。     

Dynamics of wind-rail vehicle-bridge systems

An analytical model for dynamics of wind-vehicle-bridge (WVB) systems is presented in this paper in the time domain with wind, rail vehicles and bridge modeled as a coupled vibration system. The analytical model considers many special issues in a WVB system, which include fluid-solid interaction between wind and bridge, solid contact between vehicles and bridge, stochastic wind excitation on vehicles and bridge, time dependence of the system due to vehicle movement, and effect of bridge deck on vehicle wind load and vice versa. The models of wind, vehicles and bridge are presented with wind velocity fluctuations simulated using the simplified spectral representation method, with vehicles modeled as mass-spring-damper systems, and with bridge represented by a finite element model. The interactions between wind and bridge are similar to those considered in conventional buffeting analysis for long span bridges. In considering difficulties in measuring aerodynamic coefficients of moving vehicles on bridge deck, the cosine rule is adopted for the aerodynamic coefficients of moving vehicles to consider yaw angle effect, and expressions of wind forces on moving vehicles are then derived for engineering application. To include mutual effects of wind loads, aerodynamic parameters of vehicles and bridge deck are measured, respectively, using a composite section model test and a specially designed test device. The dynamic interaction between vehicle and bridge depends on both geometric and mechanical relationships between wheels of vehicles and rails on the bridge deck. The equations of motion of the coupled WVB system are derived and solved with a nonlinear iterative procedure. A cable-stayed bridge in China is finally selected as a numerical example to demonstrate dynamic interaction of the WVB system. The results show the validity of the present model as well as wind effects on the rail vehicles and the bridge.     

Moving train loads identification on a continuous steel truss girder by using dynamic displacement influence line method

This paper presents a dynamic displacement influence line method for moving load identification on bridge. The finite element model of Poyang Lake continuous truss bridge-train systems is established and the dispersed modal shapes are acquired by modal analysis. Multi-axle moving train loads are identified with simulated annealing genetic algorithm by minimizing the errors between the measured displacements and the reconstructed displacements from the identified moving loads. In the identification process, the dynamic displacement influence line technique is used to calculate the time history displacement responses of the bridge to avoid solving equations of motion of the bridge repetitively. Several important parameters of the bridge-train system are discussed to investigate their effects on the proposed method. The results demonstrate that the proposed method is an accurate and efficient method for moving train load identification on complex bridges.     

实际车辆荷载作用下的预应力混凝土连续梁桥动力响应分析及验证

以一座三跨单箱单室预应力混凝土连续箱梁桥为对象,利用车辆-桥梁耦合振动关系建立单梁车辆、桥梁运动微分方程,通过二者变形协调、相互作用力协调关系实现车辆-桥梁的耦合关系;修正了自编的桥梁动力响应计算程序,通过建立在桥梁上的高速弯板称重系统实现对实际过桥交通荷载的识别,并将识别出的实际车辆荷载信息输入已建立的桥梁动力响应计算程序,快速计算出在实际车辆荷载作用下的桥梁动力响应,并利用ANSYS软件进行静力验证,用实际过桥车流产生的动应变进行动力验证。     

A 3D Evaluation Method for Rail–Highway Hump Crossings

Rail–highway grade crossing crashes may be caused by long vehicles with low clearances becoming stranded when attempting to negotiate rail–highway crossings with steeply graded profiles—hump crossings. Although design standards have been established to encourage the construction that most vehicles are able to successfully navigate, the combination of grade profile and cross‐section interacting with unique vehicle dimensions may lead to instances where vehicles may have difficulty crossing. This article describes a three‐dimensional (3D)‐based (LiDAR) methodology to identify and evaluate the severity of hump crossings. A five‐level criterion is proposed to rate the magnitude of contact. The methodology is demonstrated by modeling seven common low‐clearance vehicle types at three types of hump crossings. Field testing indicates a good correlation between the predicted degree of vehicle‐crossing conflicts and those observed in the field. Results are applicable to operations (e.g., truck routing) or for maintenance and reconstruction programs. Future research could extend the methodology to tunnel and bridge clearances, real‐time warning systems, autonomous vehicles, or even nontransportation applications.     

A modified numerical VBI element for vehicles with constant velocity including road irregularities

There has been a growing interest to model and analyze Vehicle-Bridge Interaction (VBI) of intricate vehicles on bridges. The objective of such an analysis is to realistically investigate the dynamic effects of moving vehicles particularly in case of high-speed trains, where the vehicle acceleration is a design criterion and should be calculated appropriately. One method of analysis is to eliminate the wheel degrees of freedom (DOF) that are in direct contact with the bridge surface resulting in a VBI element, which is a modified beam element acted upon directly by wheel(s) of a running vehicle. The contact force is the mutual force between the wheel and the bridge. The available formulation in the literature is used to formulate the contact forces, which are related to those in the beam element DOFs by the Hermitian interpolation functions. Considering suitable interpolation functions between the beam element displacement vector and those for contact points and also a new formulation for the contact points, a new formulation is proposed for the structural properties of the VBI element, resulting in a new element capable of capturing bridge and vehicle responses more realistically. A study is conducted on the model variables and their effects on the bridge dynamic amplification factor and also bridge and vehicle accelerations, in order to compare the new VBI method with the existing one. The studied parameters include vehicle and bridge damping, frequency parameter, system mass parameter, and a new parameter called vehicle mass parameter. Results generally demonstrate noticeable differences particularly for high speed vehicles. In addition, it is observed that the effect of shear deformations in a simply-supported bridge might not be negligible and should be considered for moving vehicle analysis. For double girder open-deck steel railway bridges, the difference in midspan deflection of models including or excluding shear deformation can vary from 18% to 8% for 4.0 m and 30.0 m spans, respectively, for a sample vehicle.     

近断层地震作用下斜拉桥黏滞阻尼器参数简化设计方法

黏滞阻尼器是漂浮体系斜拉桥常用的减震耗能装置,但传统的阻尼器参数设计需要通过反复的非线性有限元时程计算来确定,这种方法不够简便有效。本文根据近断层地震的脉冲特点以及斜拉桥动力特性,通过建立斜拉桥的双质点模型的运动微分方程,推导出近断层脉冲作用下的动力反应计算公式;并基于等效线性化方法,得到非线性黏滞阻尼器参数与等效阻尼比的关系,从而利用主梁目标位移反向确定所需设置的黏滞阻尼器参数;最后通过一座斜拉桥实例验证本文方法的正确性,并提出了黏滞阻尼器参数设计简化方法的流程。     

Effect of approach span condition on vehicle-induced dynamic response of slab-on-girder road bridges

The present study investigates the effect of approach span conditions on a bridge’s dynamic response induced by moving vehicles. After developing a 3D bridge–vehicle interaction model for numerical prediction, a dynamic test on a full scale slab-on-girder bridge is conducted with dump trucks to validate the developed numerical methodology. A wooden plank is used to simulate the large faulting between the bridge deck and the approach slab. With consideration of the road surface profile and approach span condition, the predicted dynamic response of the bridge is compared to the experimental results, and they show a satisfactory agreement. The numerical model is also applied to investigate the effect of the approach span condition on the dynamic behavior of the bridge induced by the AASHTO HS20 truck. A parametric study is eventually conducted by changing the road surface condition and the faulting value. The faulting condition of the approach span is found to cause significant dynamic responses for the slab-on-girder bridges and to have a considerable effect on the distribution of impact factors along the transverse and longitudinal directions. Furthermore, impact factors obtained from the numerical analyses are compared with those values specified in the AASHTO codes.     

A methodology for obtaining spatiotemporal information of the vehicles on bridges based on computer vision

Spatiotemporal information of the vehicles on a bridge is important evidence for reflecting the stress state and traffic density of the bridge. A methodology for obtaining the information is proposed based on computer vision technology, which contains the detection by Faster region‐based convolutional neural network (Faster R‐CNN), multiple object tracking, and image calibration. For minimizing the detection time, the ZF (Zeiler & Fergus) model with five convolutional layers is selected as the shared part between Region Proposal Network and Fast R‐CNN in Faster R‐CNN. An image data set including 1,694 images is established about eight types of vehicles for training Faster R‐CNN. Combined with the detection of each frame of the video, the methods of multiple object tracking and image calibration are developed for acquiring the vehicle parameters, including the length, number of axles, speed, and the lane that the vehicle is in. The method of tracking is mainly based on the judgment of the distances between the vehicle bounding boxes in virtual detection region. As for image calibration, it is based on the moving standard vehicles whose lengths are known, which can be regarded as the 3D template to calculate the vehicle parameters. After acquiring the vehicles' parameters, the spatiotemporal information of the vehicles can be obtained. The proposed system has a frame rate of 16 fps and only needs two cameras as the input device. The system is successfully applied on a double tower cable‐stayed bridge, and the identification accuracies of the types and number of axles are about 90 and 73% in the virtual detection region, and the speed errors of most vehicles are less than 6%.     

移动车辆载荷作用下桥梁动态响应(Ⅰ)

在车辆不同速度作用下桥梁的变形有其复杂性,对其研究为工程界所广泛关注。本文利用AN-SYS软件建立了桥梁的有限元模型,通过数值模拟计算分析了车辆以不同速度通过桥梁时,桥体发生的动态响应特征,从而为移动荷载作用下桥梁振动控制措施的改进提供依据。     

Estimation of gross weight,suspension stiffness and damping of a loaded truck from bridge measurements

Particle filter method (PFM) based on Bayesian inference gives a reliable estimate of hidden parameters from the noisy measured signal. A new method of vehicle parameter identification based on measured bridge response has been proposed using PFM. An uncoupled iterative technique is utilised for solving bridge vehicle interaction problem which has been used as a forward solution of the PFM. A field test under moving truck has been conducted on an existing pre-stressed concrete bridge to collect response data at different locations. Based on the extracted bridge natural frequencies and measured peak acceleration responses at five sensor locations, finite element model of the tested bridge has been updated using response surface-based model updating technique. In addition to estimation of test truck parameters using measured bridge response, dynamic wheel load induced in the bridge has been determined. Excellent agreement has been found between the measured and reconstructed bridge response using estimated parameters.     

风-汽车-桥梁系统空间耦合振动研究

为了考虑侧风引起的车轮相对于桥面的侧向相对滑动,在车轮与桥面之间引入了一个特殊阻尼器,这个阻尼器的阻尼系数依赖于车辆与桥梁的竖向耦合运动。在综合考虑路面粗糙度、车辆悬挂系统以及车轮相对于桥面侧向相对滑动的基础上,提出能够考虑桥梁的静风响应、抖振响应、汽车-桥梁耦合振动、系统的时变特性以及结构几何非线性和气动荷载非线性影响的风-汽车-桥梁系统空间耦合振动分析模型,编制了相应的分析程序。该程序既可以预测不同路面粗糙度,车速以及干、湿、雪、冰路面状况下行驶于桥梁上车辆的行车安全性,也可以评价低风速下车辆驾驶舒适度以及侧风和车辆移动荷载对桥梁振动的影响。     

移动车辆对桥梁动力作用模拟简化方法的研究

对移动车辆作用下桥梁的动力反应进行研究,分别采用移动荷载和移动质量两种形式模拟车辆,通过分析桥梁在动力荷载作用下的振动方程及其挠度极值变化情况,指出自重及惯性力在桥梁挠度变形中起到的重要作用,比较了两种方法的可靠性及其适用条件。     

交通荷载作用下大跨悬索桥的非线性动力响应分析

研究了非线性系统的等价线性化动力分析方法以及大跨悬索桥非线性特性的表征,采用移动荷载模型分析了润扬长江大桥悬索桥在移动交通荷载作用下的非线性动力响应特征,包括单车过桥、车队单向过桥、车队双向过桥以及基于实测交通流量的连续车流过桥等4种工况。结果表明,在60～120km/h的正常行车状态下,车速对结构动力响应的影响并不显著;车重与结构挠度响应呈近似正比例关系;在连续车流作用下,动力响应最显著的部位为跨中区段;在不连续车流作用下,动力响应最显著的部位为L/8～L/4区段。本文的结论可以为大跨悬索桥梁的构造优化设计、空间疲劳分布效应研究及日常养护工作提供参考。     

Framework of vehicle–bridge–wind dynamic analysis

This paper presents a framework of dynamic analysis of coupled three-dimensional vehicle–bridge system under strong winds. A general formulation of this system is introduced to simulate a series of vehicles consisting of different numbers and different types of vehicles running on bridges under hurricane-induced strong winds. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers, considering wind and road roughness loads. With this vehicle–bridge model, coupled dynamic analysis of vehicles running on bridges is conducted with a numerical example. Effects of driving speeds on the dynamic performance of the vehicles as well as the bridge are discussed. It is found that the driving speeds mainly affect the vehicle's vertical relative response while they have insignificant effect on the rolling response of vehicles. Vehicle's absolute response is dominated by the bridge response when wind speed is high, while it is dominated by road roughness when the wind speed is low. Detailed accident analysis of vehicles on bridges under strong winds will be reported in an accompanying paper.     

Damage scenario analysis of bridges using crowdsourced smartphone data from passing vehicles

Bridge wear and deterioration occur over time under typical operations. Inspections can be resource intensive, infrequent, and sometimes require bridge closure. Instrumented passing vehicles may be used to record vibration responses and extract damage-sensitive bridge frequency response characteristics. This paper presents a methodology for extracting bridge frequencies from crowdsourced dynamic response data recorded within passing vehicles. Detected bridge frequency changes and a novel point cloud methodology are used to identify critical damage scenarios and estimate remaining life. The use of a novel crowdsourced Welch methodology allows for spectra averaging that reduces the influence of noise and transient events. Numerical and experimental studies illustrate that bridge frequencies can be accurately estimated and that changes in bridge frequency caused by different damage scenarios can be characterized. Numerical examples for the damage scenario analysis, including estimation of remaining life, are provided for two bridge types and three specific damage scenarios.     

Finite element reliability analysis of bridge girders considering moment–shear interaction

Reliability analysis is necessary in bridge design to determine which parameters have the most significant influence on the structural response to applied loadings. To support finite element reliability applications, analytical response sensitivities are derived with respect to uncertain material properties, girder dimensions, reinforcing details, and moving loads by the direct differentiation method (DDM). The resulting expressions have been implemented in the general finite element framework OpenSees which is well suited to the moving load analysis of bridges. Numerical examples verify the DDM response sensitivity equations are correct, then a first-order reliability analysis shows the effect uncertain parameters have on the interaction of negative moment and shear force near the supports of a continuous reinforced concrete bridge girder. A unique contribution is the treatment of moment–shear interaction using Lamé curves with foci calculated from MCFT equations. In addition, the analysis demonstrates non-seismic bridge engineering applications that have been developed in the OpenSees framework.     

基于车桥振动接触加速度的桥梁频率识别

本文以连续梁桥为研究对象,研究车辆和桥梁的接触点响应问题.依据实际桥梁参数,建立车桥有限元模型,获取车辆响应,通过中心差分法,计算出接触点加速度,进而识别出桥梁频率.数值模拟结果表明,在平整条件下,通过车辆的接触点响应识别桥梁频率优于车辆响应识别;在粗糙条件下,桥梁频率难以很好识别,为了更清晰、更直观得出较好的桥梁频率...     

Nonlinear seismic assessment of isolated high-speed railway bridge subjected to near-fault earthquake scenarios

Abstract

An iterative framework is introduced in this present study to detect seismic isolation precursors of the shortcut calculation method for the isolated benchmark high-speed railway RC bridge. The spatial finite element (FE) analysis model of a benchmark isolated high-speed railway reinforced concrete (RC) bridge system under high-speed railway vehicles is set up based on the equivalent linear method. The vehicle with two bogies is assumed to be represented by a 3?D discrete rigid multi-body system with 23 degrees of freedoms (DOFs). The present study compares the nonlinear seismic response of a high-speed railway bridge with and without isolation bearings. Numerical results demonstrate that the isolation system with the optimal parameters can simultaneously reduce the deck displacement and the internal force of the isolated railway bridge under near-fault (NF) ground motions with various peak accelerations and peak velocity ratios, to ensure the adequate isolation efficiency of isolated structures. Specifically, the study shows that the seismic response of the seismically isolated bridge (IB) and the running safety indexes of the train are primarily dominated by the contents around the fundamental frequency of the train-bridge system subjected to the earthquakes.     

简支梁桥位移与内力动力系数差异研究

动力系数是桥梁结构设计和检定中一个基本而关键的参数,其可以用位移放大系数来表示,也可以用内力(弯矩、剪力)放大系数来表示,而在桥梁的设计、检定工作中,并未注意到它们量值之间的区别.文中理论探讨了移动荷载列过桥模型的位移、内力放大系数的异同,以及不同动力系数沿简支梁桥跨长的变化规律,为区分制定桥梁动力系数的合理表达形式提供理论依据.并计算分析了车桥耦合模型与移动荷载列过桥模型的桥梁动力系数计算值的差异,结果表明应用移动荷载列模型计算简支梁桥动力系数可以得到安全可靠的结果,即可应用该模型解析解分析动力系数的主要影响因素.