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Numerical study of reactive pollutants diffusion in urban street canyons with a viaduct

Building Simulation 2022年第7期15卷 1227-1241页

作者： Tingzhen Ming Cao Nie Wenyu Li Xin Kang Yongjia Wu Mengjie Zhang Chong Peng School of Civil Engineering and Architecture Wuhan University of TechnologyWuhan 430070China School of Architectural Engineering Huonggang Normal UniversityNo.146 Xingang Second RoadHuanggang 438000China Mechanical Engineering Department University of CaliforniaBerkeleyCA 94720USA School of Urban Planning and Architecture Huazhong University of Science and TechnologyWuhan 430074China

In this paper,the influences of the ambient wind speed and the height and width of a viaduct in a 2-dimensional street canyon on the diffusion of reactive pollutants emitted by motor vehicles were investigated using computational fluid dynamics(CFD)method.Pollutants were treated as reactive by including a NO-NO_(2)-O_(3) photochemical reaction mechanism in the simulation.The Reynolds-averaged Navier-Stokes(RANS)k-ε turbulence model and the discrete phase model were used to simulate the airflow movement and the concentration distribution,respectively,of the reactive pollutants in the street canyon.Three indices,i.e.,the chemical reaction contribution of NO(CRC_(NO)),the chemical reaction contribution of NO_(2)(CRC_(NO_(2))),and the O_(3) depletion rate,were used to evaluate the relative importance of the photochemical reactions.It was found that the presence of a viaduct changed the flow field structure in the street canyon.The CRC_(NO) and CRC_(NO_(2))decreased from the windward side to the leeward side of the canyon.The maximum values of the CRC_(NO) and CRC_(NO_(2)) were observed at the pollution source(x=245 m)due to the influence of a clockwise vortex in the street canyon.As the height and width of the viaduct increased,concentration of the ground pollutants and the O_(3) depletion rate increased.The O_(3) depletion rate was much higher on the leeward side(90%)than on the windward side.The pollutant concentrations after the reaction were twice as high with the viaduct as without the viaduct when the viaduct height was the same as the building height.The viaduct had a significantly larger influence on the concentration of the reactive pollutants than the chemical reactions.The O_(3) depletion rate in the canyon and the pollutant concentrations decreased as the ambient wind speed increased,whereas the CRC_(NO_(2)) increased.

关键词： street canyon viaduct reactive pollutant-photochemical reaction CFD

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A substructure approach for analyzing pile foundation and soil vibrations due to train running over viaduct and its validation

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Railway Engineering Science 2022年第4期30卷 468-481页

作者： Ying Wu Xuecheng Bian Chong Cheng Jianqun Jiang Department of Civil Engineering MOE Key Laboratory of Soft Soils and Geoenvironmental EngineeringZhejiang UniversityAnzhong Building of Civil Engineering B406Zijingang CampusHangzhou 310058China

An efficient computational approach based on substructure methodology is proposed to analyze the viaduct-pile foundation-soil dynamic interaction under train loads.Thetrain-viaductsubsystemissolvedusingthe dynamic stiffness integration method,and its accuracy is verified by the existing analytical solution for a moving vehicle on a simply supported beam.For the pile foundation-soil subsystem,the geometric and material properties of piles and soils are assumed to be invariable along the azimuth direction.By introducing the equivalent stiffness of grouped piles,the governing equations of pile foundation-soil interaction are simplified based on Fourier decomposition method,so the three-dimensional problem is decomposedintoseveraltwo-dimensionalaxisymmetricfinite element models.The pile foundation-soil interaction model is verified by field measurements due to shaker loading at pile foundation top.In addition,these two substructures are coupled with the displacement compatibility condition at interface of pier bottom and pile foundation top.Finally,the proposed train-viaduct-pile foundation-soil interaction model was validated by field tests.The results show that the proposed model can predict vibrations of pile foundation and soil accurately,thereby providing a basis for the prediction of pile-soil foundation settlement.The frequency spectra of the vibration in Beijing-Tianjin high-speed railway demonstrated that the main frequencies of the pier top and ground surface are below 100 and 30 Hz,respectively.

关键词： Train moving load viaduct Pile foundation Soil Vibration Substructure method

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Propagation characteristics of wideband high-speed railway channel in viaduct scenario at 2.35 GHz

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Journal of Modern Transportation 2012年第4期20卷 206-212页

作者： Yunling GUO Jianhua ZHANG Cheng TAO Liu LIU Lei TIAN Key Laboratory of Universal Wireless Communications (Ministry of Education) Wireless Technology Innovation Institute Bei-jing University of Posts and Telecommunications Institute of Broadband Wireless Mobile Communications Beijing Jiaotong University

In order to obtain accurate characteristics of wireless channels in the viaduct area of China, a channel meas- urement was taken in a railway viaduct scenario of the Zhengzhou-Xi＇an passenger dedicated line with a bandwidth of 50 MHz at 2.35 GHz. The single-slope log-distance model is used to analyze the path-loss （PL）, and the distribution of shadow fading （SF） is obtained by statistical methods, which shows that the normal distribution fits the samples well. Ricean K-factor is analyzed by the method of moments, and the variation of K-factor is given along the measured route. Small scale such as delay spread and Doppler behavior are parameterized. Based on empirical channel measurement, this paper provides parameters for the evaluation and simulation work on viaduct scenarios of high-speed railway.

关键词： high-speed railway channel measurement viaduct path-loss delay spread Ricean K-factor Doppler

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Discrete-Event Simulation of viaduct Construction Methods in Riyadh Metro

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Journal of Civil Engineering and Architecture 2021年第12期15卷 604-613页

作者： Khalid S.Al-Gahtani Ibrahim A.Al-Sulaihi Hassan T.Al-Assafi College of Engineering Civil Engineering DepartmentKing Saud UniversityP.O.Box 800Riyadh 11421Saudi Arabia

The Riyadh metro project is one of the current megaprojects that aim to improve the transit systems in Saudi Arabia.It consists of several metro lines with a total length of 176 km and 85 stations.The viaducts are considered as one of the main construction elements in the metro lines.Four methods for viaducts construction have been used in the Riyadh metro project:precast beam,full span launching method,cast on-site,and segment method(precast segment method and BCM(balanced cantilever method)).The viaducts work consumes a large portion of a project’s time and cost.Furthermore,the competitive nature of the construction industry increases the need to improve the efficiency of construction performance.Accordingly,this paper takes the initial steps toward increasing the efficiency of viaduct construction methods through simulation.Simulation of construction processes provides a systematic tool that can be used for determining the resources,time,and cost of these processes.The simulation processes should focus on the main activities affecting this element’s execution for viaducts construction,such as segment storage,handling,transporting,and installation.This study highlights the viaducts construction methods and develops general discrete-event simulation models for the most commonly used viaducts construction methods in the Riyadh metro using AnyLogic simulation software.The simulation models visualize and capture the interaction between the different activities and resources in a viaduct construction.Consequently,the construction drawbacks can be identified.Furthermore,the simulation model can be manipulated by adding assumptions to develop more efficient construction methods in terms of time and cost in such projects.

关键词： Simulation viaduct construction AnyLogic discrete event Riyadh metro

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Analysis of Propagation Characteristics of Electromagnetic Disturbance from the Off-Line of Pantograph-Catenary in High-Speed Railway viaducts

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Chinese Journal of Electronics 2020年第5期29卷 966-972页

作者： LI Meng WEN Yinghong SUN Xiaokang WANG Guodong School of Electronic and Information Engineering Beijing Jiaotong University Beijing Engineering Research Center of EMC and GNSS Technology for Rail Transportation Hangzhou Hikvision Digital Technology Co. Ltd.

Pantograph arcing caused by Off-line of pantograph-catenary(OLPC) will generate Electromagnetic disturbance(EMD), which will affect train control system and communication system. This paper proposes a simplified model of the train and pantograph to investigate propagation characteristics of EMD from OLPC in the viaduct scenario, containing attenuation law in transverse and longitudinal directions. As a result, the electric field strength of EMD from OLPC increases with distance in transverse direction from 10 m to 30 m in the viaduct scenario, which is different from the ground scenario. Thefitting formulas are found to research the attenuation law at different frequency points. We get the conclusion that the limit and measurement distance is not applicable for the viaduct scenario in current standard. To prove this,measurement in the viaduct scenario is completed, and the plausible evidence to explain the result is discussed.These results are useful in the measurement of radiated emissions, on-board equipment layout and the research of standard in high-speed railway.

关键词： Electromagnetic disturbance (EMD) Off-line of pantograph-catenary (OLPC) Propagation Measurement viaduct

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Design of bridges against large tectonic deformation

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Earthquake Engineering and Engineering Vibration 2008年第4期7卷 345-368页

作者： I.Anastasopoulos G.Gazetas V.Drosos T.Georgarakos R.Kourkoulis National Technical University

The engineering community has devoted much effort to understanding the response of soil-structure systems to seismic ground motions, but little attention to the effects of an outcropping fault offset. The 1999 earthquakes of Turkey and Taiwan, offering a variety of case histories of structural damage due to faulting, have （re）fueled the interest on the subject. This paper presents a methodology for design of bridges against tectonic deformation. The problem is decoupled in two analysis steps： the first （at the local level） deals with the response of a single pier and its foundation to fault rupture propagating through the soil, and the superstructure is modeled in a simplified manner; and the second （at the global level） investigates detailed models of the superstructure subjected to the support （differential） displacements of Step 1. A parametric study investigates typical models of viaduct and overpass bridges, founded on piles or caissons. Fixed-head piled foundations are shown to be rather vulnerable to faulting-dnduced deformation. End-bearing piles in particular are unable to survive bedrock offsets exceeding 10 cm. Floating piles perform better, and if combined with hinged pile-to-cap connections, they could survive much larger offsets. Soil resilience is beneficial in reducing pile distress. Caisson foundations are almost invariably successful. Statically-indeterminate superstructures are quite vulnerable, while statically-determinate are insensitive （allowing differential displacements and rotations without suffering any distress）. For large-span cantilever-construction bridges, where a statically determinate system is hardly an option, inserting resilient seismic isolation bearings is advantageous as long as ample seating can prevent the deck from falling off the supports. An actual application of the developed method is presented for a major bridge, demonstrating the feasibility of design against tectonic deformation.

关键词： fault rupture earthquake soil-structure interaction bridge viaduct pile group caisson foundation finite elements

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High-speed railway channel measurements and characterizations: a review

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Journal of Modern Transportation 2012年第4期20卷 199-205页

作者： Tao ZHOU Cheng TAO Liu LIU Jiahui QIU Rongchen SUN Institute of Broadband Wireless Mobile Communications Beijing Jiaotong University

Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

关键词： high-speed railways wireless communication channel measurement viaduct U-shaped groove

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成层成串

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建筑创作 2005年第2期 78-79页

该设计项目位于Holborn viaduct，这个地区的空间非常紧凑，考虑到这一点，建筑的设计也十分紧凑，就像一座微型城市，里面有两种相反但相互呼应的空间体系，经典的现代堆叠板体系（多米诺体系），

关键词：建筑设计建筑空间 Holborn viaduct 建筑结构板式结构

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