Bridge Structural Condition Assessment Based on Vibration and Traffic Monitoring

A stochastic model of traffic excitation on bridges is developed assuming that the arrival of vehicles traversing a bridge (modeled as an elastic beam) follows a Poisson process, and that the contact force of a vehicle on the bridge deck can be converted to equivalent dynamic loads at the nodes of the beam elements. The parameters in this model, such as the Poisson arrival rate and the stochastic distribution of vehicle speeds, are obtained by image processing of traffic video data. The model reveals that traffic excitations on bridges are spatially correlated. This important characteristic is usually incorrectly ignored in most output-only methods for the identification of bridge structural properties using traffic-induced vibration measurement data. In this study, the stochastic traffic excitation model with partial traffic information is incorporated in a Bayesian framework, to evaluate the structural properties and update their uncertainty for condition assessment of the bridge superstructure. The vehicle weights are also estimated simultaneously in this procedure. The proposed structural assessment methodology is validated on an instrumented highway bridge.     

Analysis of Traffic-Induced Vibrations in a Cable-Stayed Bridge. Part II: Numerical Modeling and Stochastic Simulation

This paper describes the development of a numerical model to simulate the dynamic response of the bridge–vehicle system of Salgueiro Maia cable-stayed bridge, using the results from an extensive experimental investigation to calibrate this model. Further, a set of stochastic Monte Carlo simulations of the bridge–vehicle dynamic response is also presented, with the purpose of evaluating dynamic amplification factors, taking into account the randomness of different factors associated to characteristics of the pavement, of the vehicles and of the traffic flow.     

Noise Evaluation for Pavement Maintenance in Metropolitan Highway Bridges

Dynamic response of a bridge under traffic load induces acoustic energy at the bridge surface. The acoustic energy change generates an additional coupled noise component caused by vibration of a bridge deck associated with the pavement conditions and moving velocity of the vehicle. This paper presents a three-dimensional finite-element method developed for the dynamic response and noise propagation model, and analyzes the coupled effect induced by traffic loading based on different pavement conditions. Even though vibration-induced noise at the bridge is below the audible frequency range of 20–20,000?Hz, it amplifies the traffic noise source to the highly annoyed level of noise in the metropolitan area. Among several factors that contribute to the traffic noise, interaction between pavement and vehicle is considered according to the different surface roughness and vehicle velocity. The result shows that poor pavement condition contributes to the increase of traffic noise at a high traveling speed of the vehicle. In the pavement maintenance stage, the coupled effect as an additional noise source should be considered to mitigate the traffic noise for its added value in conjunction with regulation of engine emission noise and construction of a noise barrier.     

Dynamic Response Solution in Transient State of Viscoelastic Road under Moving Load and Its Application

In order to study the dynamic response of an asphalt road, a dynamic model of the road under a moving load is proposed, in which the viscoelastic characteristics of the base and pavement are all considered, the pavement is regarded as an infinite beam on a Kelvin viscoelastic base. By using Green’s functions, Laplace transforms, and Fourier transforms, the analytical solution in transient is deduced. As the viscosity of the pavement is included in the model, the analytical solution can be used to investigate more of the factors that affect the dynamic response, such as vehicle speed, temperature, and road material properties. Using this analytical solution, some numerical calculations are given to illustrate the effects of vehicles’ speeds and different damping on the deflection with the displacement.     

Searching for regulatory elements in human noncoding sequences

Injury type and severity among front outboard occupants of passenger vehicles struck in the side by another passenger vehicle and recorded in the United States National Accident Sampling System Crashworthiness Data System were examined in relation to the location of impact, the angle of impact, occupant gender and age, seat belt use, the weight and body style of the side-impacted vehicle, and the weight and body style of the striking vehicle. Elderly occupants were three times as likely as younger occupants in similar crashes to be seriously injured. Serious injuries were also more likely for occupants seated on the struck side and occupants of lightweight passenger vehicles. After accounting for vehicle weight differences, struck-side occupants of cars were still much more likely to be seriously injured than struck-side occupants of light trucks. However, among occupants seated on the side of the vehicle opposite the impact, the likelihood of serious injury was higher for those seated in light trucks.     

Effects of Train Characteristics on the Rate of Deterioration of Track Roughness

Track roughness describes in part the up and down waves in the longitudinal geometry of a railway track. A train passing over rough track experiences a degree of bouncing that generates oscillations in the forces exerted by the train’s wheels on the top of the rail, which in turn cause this roughness to worsen. The rate at which the track roughness deteriorates depends on the response of the track to the weight of the train and to the dynamic oscillations in wheel/rail forces, which in turn are affected by the properties of the train vehicles’ components and the speed of the train. The paper develops relationships between the severity of track roughness and the dynamic wheel/rail forces generated by a moving train using field data, and between those forces and the specific vehicle characteristics of speed, total mass, unsprung mass, suspension stiffness, and damping, using NUCARS simulations. These two relationships in turn are combined to show how the speed of the train and the design of the train vehicle’s bogie suspension can worsen or improve the rate of deterioration of track roughness. The relationships also provide a firm basis for the owner of track to set more representative charges levied on the train operator for using the track.     

Dynamic and Impact Behavior of Half-Through Arch Bridges

The objective of this paper is to present the results of an investigation of the dynamic and impact characteristics of half-through arch bridges with rough decks caused by vehicles moving across them. Seven arch bridges modeled as three-dimensional structures with overall span lengths ranging from 20?to?200?m (65.5?to?656.2?ft) are analyzed. The American Association of State Highway and Transportation Officials Specifications HS20-44 truck is the applied vehicle loading used in the analysis and is simulated as a three-dimensional, nonlinear vehicle model with 11 degrees of freedom. Truck components include the body, suspension, and tires. The bridge deck surface is assumed to have a “good” surface roughness and is simulated using a stochastic process (power spectral density function). The effect on impact factors of span length, rise-to-span ratio, and vehicle speed is discussed. The results of the analyses show that the impact factors of bending moment and axial force will not exceed 0.4 and 0.25, respectively. The proposed impact equations are simple and conservative and can be used in the design of half-through arch bridges.     

Dynamic Performance Simulation of Long-Span Bridge under Combined Loads of Stochastic Traffic and Wind

Slender long-span bridges exhibit unique features which are not present in short and medium-span bridges such as higher traffic volume, simultaneous presence of multiple vehicles, and sensitivity to wind load. For typical buffeting studies of long-span bridges under wind turbulence, no traffic load was typically considered simultaneously with wind. Recent bridge/vehicle/wind interaction studies highlighted the importance of predicting the bridge dynamic behavior by considering the bridge, the actual traffic load, and wind as a whole coupled system. Existent studies of bridge/vehicle/wind interaction analysis, however, considered only one or several vehicles distributed in an assumed (usually uniform) pattern on the bridge. For long-span bridges which have a high probability of the presence of multiple vehicles including several heavy trucks at a time, such an assumption differs significantly from reality. A new “semideterministic” bridge dynamic analytical model is proposed which considers dynamic interactions between the bridge, wind, and stochastic “real” traffic by integrating the equivalent dynamic wheel load (EDWL) approach and the cellular automaton (CA) traffic flow simulation. As a result of adopting the new analytical model, the long-span bridge dynamic behavior can be statistically predicted with a more realistic and adaptive consideration of combined loads of traffic and wind. A prototype slender cable-stayed bridge is numerically studied with the proposed model. In addition to slender long-span bridges which are sensitive to wind, the proposed model also offers a general approach for other conventional long-span bridges as well as roadway pavements to achieve a more realistic understanding of the structural performance under probabilistic traffic and dynamic interactions.     

Response Spectral Density for Oscillators with Nonlinear Damping

The concept of equivalent nonlinearization is used to obtain approximate solutions for the frequency response function and power spectral density (PSD) function of the response for oscillators with nonlinear damping. When harmonic excitation is considered the energy of the response is assumed to oscillate around a mean energy level. Assuming that the response is harmonic with energy-dependent amplitude an approximate frequency response function is obtained. The PSD function of the response to white noise excitation at a given energy level is obtained by an expression similar to the expression for a linear system, where the damping is replaced by an energy-dependent damping function. The total PSD function is obtained as a weighted average of the damping at all energy levels, and the method can be considered an extension of the method of equivalent nonlinearization to the frequency domain. The accuracy of the methods is verified by numerical examples.     

Vehicle Condition Surveillance on Continuous Bridges Based on Response Sensitivity

This paper presents the parameter identification of a vehicle moving on a multispan continuous bridge deck modeled as a continuous beam based on dynamic response sensitivity analysis. This technique is for the monitoring of “road-friendliness” of vehicles using the highway pavement. The moving vehicle is modeled as a single degree-of-freedom system comprising three parameters, a two degrees-of-freedom system comprising five parameters, or a four degrees-of-freedom system comprising 12 parameters. The modified beam functions are used to calculate the response of the continuous bridge. Starting with an initial guess on the unknown parameters, the identification can be realized based on least-squares method and regularization technique from measured strain, velocity, or acceleration measurement from as few as a single sensor. Simulation studies and experimental results indicate that the identified results are acceptable, and the responses reconstructed from the identified parameters agree well with the measured responses.     

Safety Analysis of Moving Road Vehicles on a Long Bridge under Crosswind

This paper presents a safety analysis of high-sided road vehicles running on a long span cable-stayed bridge when the road vehicle enters a sharp-edged crosswind gust while the bridge is oscillating under fluctuating winds. Road vehicle accidents, including overturning, excessive sideslip, and exaggerated rotation, are defined first. The mathematical model and the equation of motion of coupled road vehicle–bridge systems under crosswind are then established, which include road surface roughness, vehicle suspension, and the sideslip of the vehicle tire relative to the bridge deck in the lateral direction. A case study using a real long cable-stayed bridge and a high-sided road vehicle is finally conducted, and an extensive computational work is performed to obtain a series of accident vehicle speed against mean crosswind speed, by which the decision on the threshold of mean wind speed above which the bridge should be closed to the road vehicle can be made. The obtained accident vehicle speeds are also compared with those for the same vehicles running on the ground. It is shown that the oscillation of the cable-stayed bridge will lower the accident vehicle speed when wind speed reaches a certain level.     

Factors Affecting Initial Roughness of Concrete Pavement

Past studies have shown that initial pavement roughness greatly affects future pavement roughness and roughness progression rate. Initial pavement roughness is also an important input to the roughness prediction model in mechanistic-empirical design guide. This study analyzed the design and construction factors affecting initial pavement roughness. Initial international roughness index of 90 concrete pavements constructed in Wisconsin from 2000 to 2004 were analyzed using multiple regression method. The factors considered in this study included concrete pavement slab thickness, project location, dowel bar placement, joint spacing, base type, and pavement length. The factors affecting initial pavement roughness were identified.     

Dynamic Behavior of Deck Slabs of Concrete Road Bridges

This paper treats the dynamic effect of traffic actions on the deck slabs of concrete road bridges using the finite-element method. All the important parameters that influence bridge-vehicle interaction are studied with a systematic approach. An advanced numerical model is described and the results of a parametric study are presented. The results suggest that vehicle speed is less important than vehicle mass and that road roughness is the most important parameter affecting the dynamic behavior of deck slabs. The type of bridge cross section was not found to have a significant influence on deck slab behavior. The dynamic amplification factor varied between 1.0 and 1.55 for the bridges and vehicles studied. These results should be validated by further work.     

Natural Frequency of Railway Girder Bridges under Vehicle Loads

To investigate the natural frequency of a railway girder bridge under vehicle loads, two methods are presented. First, the natural frequency of a railway girder bridge under vehicle loads is obtained by solution of the eigenvalue of the vehicle-bridge interaction equation at each step of the numerical integration. Second, based on the vehicle-bridge interaction equation, an approximate formula is developed. The results show that the natural frequency of a railway girder bridge under vehicle loads varies periodically as the vehicles pass over the bridge. The results obtained with the two methods are then compared, showing that a good agreement is achieved. From parametric studies, the effects of the unsprung mass, the sprung mass, and the stiffness of the vehicle suspension are discussed.     

Computer Model for Life-Cycle Cost Analysis of Roadway Pavements

This paper describes the development of a computer model that performs life-cycle cost analysis (LCCA) of roadway pavements, analyzing the cost of both the agency and the user. Agency costs are a function of the type of rehabilitation, restoration, resurfacing, or reconstruction (i.e., 4R) treatment applicable to each pavement type, given its surface distress and structural condition. The cost of each treatment is calculated from the unit prices specified for the activities involved and the roadway geometry. User costs include vehicle operating and nonvehicle operating costs, which are a function of pavement roughness, as well as user delay costs, which are a function of lane closure practice. User benefits are calculated as savings in user costs due to reduction in pavement roughness from its current state to that of a new pavement. At the roadway network level, sections are flagged for analysis in decreasing benefit-cost order, whereby the cost of the most capital-intensive 4R treatment is considered. Sections flagged at the network level are carried forward to the project level analysis. The project level analysis allocates the available budget among the sections selected to maximize user benefits over the analysis period. The software package implementing this methodology, called pavement investment decisions (PID) is generic; that is, it allows customizing through a series of input screens to fit the pavement management database and practices of any state Department of Transportation (DOT).     

基于增强学习算法的插电式燃料电池电动汽车能量管理控制策略

以一款插电式燃料电池电动汽车(plug-in fuel cell electric vehicle,PFCEV)为研究对象,为改善燃料电池氢气消耗和电池电量消耗之间的均衡,实现插电式燃料电池电动汽车的燃料电池与动力电池之间的最优能量分配,考虑燃料电池汽车实时能量分配的即时回报及未来累积折扣回报,以整车作为环境,整车控制作为智能体,提出了一种基于增强学习算法的插电式燃料电池电动汽车能量管理控制策略.通过Matlab/Simulink建立整车仿真模型对所提出的策略进行仿真验证,相比于基于规则的策略,在不同行驶里程下,电池均可保持一定的电量,整车的综合能耗得到明显降低,在100、200和300 km行驶里程下整车百公里能耗分别降低8.84%、29.5%和38.6%;基于快速原型开发平台进行硬件在环试验验证,城市行驶工况工况下整车综合能耗降低20.8%,硬件在环试验结果与仿真结果基本一致,表明了所制定能量管理策略的有效性和可行性.      

电动汽车集成热管理研究进展

电动汽车具有节能环保的优点，电池、乘员舱和电机驱动系统的热管理是提高其运行安全性和司乘人员舒适性的关键技术。针对电动汽车集成热管理系统构建过程中的关键问题，首先概述了电池、乘员舱和电机驱动系统的产热模型；其次系统地总结了现有的电池、乘员舱和电机驱动系统的热管理方法，重点分析了集成热管理系统的研究现状、运行控制和系统性能评价；最后总结了当前研究存在的不足并进行了研究展望，指出研究准确的产热计算模型，发展紧凑高效的集成热管理系统，在综合性能评价体系下优化集成热管理系统的运行控制是未来的主要研究方向。      

Sudden Failure of a Heavily Loaded Container Pavement

The case history of a sudden and unexpected failure in a pavement designed for 82?Mg axle loads at Port Botany in Sydney, Australia has been prepared using data derived from investigation of the failure. Failure of the pavement, comprised of an asphaltic concrete surface, unbound granular fine crushed rock base, crushed sandstone subbase, and sandy subgrade, and designed using the rational method—CIRCLY, occurred within days of being put into service. The failure resulted from a 20–30% increase in base course saturation levels following compaction that led to partial liquefaction under repeated heavy loading. There was a general failure throughout the storage area where trafficking was most intense and the pavement remained intact in lightly trafficked areas. The intact areas recovered over time without intervention through a moisture equilibration process as evidenced by an increase in measured pavement stiffness and loss of moisture within the pavement profile.     

地基土体对货车与波形梁护栏碰撞效应的影响

公路上正常行驶的车辆一旦操纵失控,安装在路侧的护栏就显得极为重要,可避免车辆直接冲出道路发生致命危险.波形梁护栏是最常见的一种被动防护装置,可有效抵御车辆施加的碰撞荷载.依据常规的设计思路,这种护栏可以利用波形梁板、防阻块和立柱的变形来吸收汽车碰撞所产生的能量.但与实际情况不同的是,在这一过程中忽略了地基土体对碰撞过程可能产生的影响.本文通过分别建立不考虑和考虑地基约束作用的碰撞计算模型来研究土体的贡献.在模拟过程中,分别观测货车的运行轨迹、护栏的变形和土体的变形.此外,也分析了不同部件对碰撞能量的吸收比率.与立柱接触区毗邻的土体因受冲击荷载影响,可能发生剪切失效.整个护栏系统中超过10%的系统能量实际上是由土体吸收的,常用的简化固定基模型跟实际情况有一定的出入.      

Dynamic Numerical Analysis of Antimoisture-Damage Mechanism of Permeable Pavement Base

As a permeable base material of pavement, the large stone porous asphalt mixture (LSPM) is used widely in China to lessen the moisture damage of the asphalt pavement. However, the dynamics mechanism of the inhibitory effect of permeable base on moisture damage is not clear yet. The dynamic fluid-solid coupling analysis of the saturated pavement with LSPM base course, considering the asphalt mixtures as the porous medium, was performed using the finite difference numerical code FLAC3D. Numerical results revealed that the positive and negative dynamic pore pressure alternated in the pavement with the approaching and leaving of the wheel loads. The phenomenon of water pumping out of and sucking into the pavement under the moving loads was proved. The flow of fluid in pavement can be regarded as the laminar flow. The presence of the LSPM base course greatly decreased the dynamic pore pressure and the scouring force in the surface course because of the large permeability coefficient of the LSPM. The location of the maximum dynamic pore pressure also changed due to the LSPM base course. Due to the permeable base, the dissipation of the dynamic pore pressure was accelerated and thus the moisture damage was lessened.