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2016 Vol.24 Issue.4,Published 2016-12-30

237 Review of recent progress in studies on noise emanating from rail transit bridges
Xiaozhen Li, Dewang Yang, Guiyuan Chen, Yadong Li, Xun Zhang
In recent years, there has been rapid growth of Chinese rail transit networks. Many of these networks require elevated bridges. This results in a bridge-borne noise source, which occurs in addition to the main noise source (i.e., wheel-rail interactions). Bridge-borne noise is attracting increasing attention because of its low-frequency noise characteristics. This review paper first analyzes the space distribution, spectral characteristics, and sound pressure levels of noise radiated by all-concrete, steel-concrete composite, and all-steel bridges, mainly according to experimental studies. Second, this paper reviews existing theoretical prediction models of noise emanating from bridges:the semianalytical method, the Rayleigh integral method, the boundary element method, and statistical energy analysis. Several case studies are reviewed, and their results are discussed. Finally, according to the results of the current review, the main factors affecting bridgeborne noise are analyzed, several noise reduction measures are proposed for different types of bridges, and their effectiveness is demonstrated.
2016 Vol. 24 (4): 237-250 [Abstract] ( 3265 ) [HTML 1KB] [ PDF 1500KB] ( 875 )
251 Simplified full-depth precast concrete deck panel systems for accelerated bridge construction
Zhongguo John Ma, Yulin Zhan, Lin Xiao, Lungui Li, Weiwei Lu
A simplified full-depth precast concrete deck panel system for accelerating bridge construction (ABC) is introduced and a finite element analysis (FEA) is conducted to investigate the static and dynamic responses of this conceptual deck system. The FEA results are compared to those of the traditional full-depth precast concrete deck panel system. The comparison results show that the mechanical behavior of the new deck system is different from that of the traditional deck system. The concrete decks in the new system act as two-way slabs, instead of the one-way slab in the traditional system. Meanwhile, the connections in both the longitudinal and transverse directions may need to accommodate the negative moments. Compared to those in the traditional system, the longitudinal nominal stress at middle span increases a lot in the new deck system and the effective flange width varies significantly. In addition, the dynamic results show that the impact factor is influenced by the spacing of connections. Finally, some design concerns of the new deck system are proposed.
2016 Vol. 24 (4): 251-260 [Abstract] ( 3424 ) [HTML 1KB] [ PDF 4356KB] ( 352 )
261 Mechanism and effects of snow accumulations and controls by lightweight snow fences
Duote Liu, Yongle Li, Bin Wang, Peng Hu, Jingyu Zhang
This paper investigates the snowdrifts caused by lightweight fences along the lines on the flatland through the computational fluid dynamics method. The characteristic ambient flows around the solid fences and the porous fences with varied heights and bottom wind gaps are simulated in the numerical model, and the working mechanism of "interception" and "scouring" of the lightweight fences are analyzed. Based on the friction velocities near the ground, two sets of criteria are proposed to evaluate the deposition and erosion effects of different fences. According to flow separation and reattachment, the simplified relationships between the most likely positions for snow accumulations and fence parameters are developed. The study indicates that the capabilities for snow interception by the solid fence without wind gap and the distance from which to the second snow coverage center both increase with the fence height. Furthermore, it is found that the scouring range for snow surface increases significantly with the size of wind gap, and the snow accumulation rate on the leeward side decreases with the increasing fence porosity.
2016 Vol. 24 (4): 261-269 [Abstract] ( 3324 ) [HTML 1KB] [ PDF 1996KB] ( 331 )
270 Analysis of the stress intensity factor of welded joints under prior corrosion and complex stress fields
Zhiyu Jie, Yadong Li, Xing Wei
Taking cruciform welded joints under different corrosion degrees, together with 45° inclined angle and full penetration load-carrying fillet, as the research object, the stress intensity factor of a quarter-circular corner crack of welded joints is calculated based on FRANC3D with ABAQUS. Effects of different corrosion pit sizes, crack aspect ratios, and crack depths on stress intensity factor are analyzed. The results show that pit depth plays a major role in stress intensity factor, while the effect of pit radius is relatively small. The cracking modes of the surface and the deepest point are mode I, and mixed modes I and II, respectively. Effects of pit depths, crack aspect ratios, and crack depths on the stress intensity factor at the surface point are greater than at the deepest point.
2016 Vol. 24 (4): 270-276 [Abstract] ( 3315 ) [HTML 1KB] [ PDF 786KB] ( 321 )
277 Verifying the accuracy of interlocking tables for railway signalling systems using abstract state machines
Basri Tugcan Celebi, Ozgur Turay Kaymakci
Railway transportation system is a critical sector where design methods and techniques are defined by international standards in order to reduce possible risks to an acceptable minimum level. CENELEC 50128 strongly recommends the utilization of finite statemachines during system modelling stage and formal proof methods during the verification and testing stages of control algorithms. Due to the high importance of interlocking table at the design state of a signalization system, the modelling and verification of interlocking tables are examined in this work. For this purpose, abstract state machines are used as a modelling tool. The developed models have been performed in a generalized structure such that the model control can be done automatically for the interlocking systems. In this study, NuSMV is used at the verification state. Also, the consistency of the developedmodels has been supervised through fault injection. The developed models and software components are applied on a real railway station operated by Metro Istanbul Co.
2016 Vol. 24 (4): 277-283 [Abstract] ( 3325 ) [HTML 1KB] [ PDF 702KB] ( 356 )
284 Autonomous vehicles: challenges, opportunities, and future implications for transportation policies
Saeed Asadi Bagloee, Madjid Tavana, Mohsen Asadi, Tracey Oliver
This study investigates the challenges and opportunities pertaining to transportation policies that may arise as a result of emerging autonomous vehicle (AV) technologies. AV technologies can decrease the transportation cost and increase accessibility to low-income households and persons with mobility issues. This emerging technology also has far-reaching applications and implications beyond all current expectations. This paper provides a comprehensive review of the relevant literature and explores a broad spectrum of issues from safety to machine ethics. An indispensable part of a prospective AV development is communication over cars and infrastructure (connected vehicles). A major knowledge gap exists in AV technology with respect to routing behaviors. Connectedvehicle technology provides a great opportunity to implement an efficient and intelligent routing system. To this end, we propose a conceptual navigation model based on a fleet of AVs that are centrally dispatched over a network seeking system optimization. This study contributes to the literature on two fronts:(i) it attempts to shed light on future opportunities as well as possible hurdles associated with AV technology; and (ii) it conceptualizes a navigation model for the AV which leads to highly efficient traffic circulations.
2016 Vol. 24 (4): 284-303 [Abstract] ( 3537 ) [HTML 1KB] [ PDF 2067KB] ( 514 )
304 Analysis of occupation time of vehicles at urban unsignalized intersections in non-lane-based mixed traffic conditions
Gowri Asaithambi, Chepuru Anuroop
In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and ignore the rules of priority. Drivers generally become more aggressive and tend to cross the uncontrolled intersections without considering the conflicting traffic. All these conditions cause a very complex traffic situation at unsignalized intersections which have a great impact on the capacity and performance of traffic intersections. A new method called additive conflict flow (ACF) method is suitable to determine the capacity of unsignalized intersections in non-lane-based mixed traffic conditions as prevailing in India. Occupation time is the key parameter for ACF method, which is defined as the time spent by a vehicle in the conflict area at the intersection. Data for this study were collected at two three-legged unsignalized intersections (one is uncontrolled and other one is semicontrolled) in Mangalore city, India using video-graphic technique during peak periods on three consecutive week days. The occupation time of vehicles at these intersections were studied and compared. The data on conflicting traffic volume and occupation time by each subject vehicle at the conflict area were extracted from the videos using image processing software. The subject vehicles were divided into three categories:two wheelers, cars, and auto-rickshaws. Mathematical relationships were developed to relate the occupation time of different categories of vehicles with the conflicting flow of vehicles for various movements at both the intersections. It was found that occupation time increases with the increasing conflicting traffic and observed to be higher at the uncontrolled intersection compared to the semicontrolled intersection. The segregated turning movements and the presence of mini roundabout at the semicontrolled intersection reduces the conflicts of vehicular movements, which ultimately reduces the occupation time. The proposed methodology will be useful to determine the occupation time for various movements at unsignalized intersections. The models developed in the study can be used by practitioners and traffic engineers to estimate the capacity of unsignalized intersections in non-lane-based discipline and mixed traffic conditions.
2016 Vol. 24 (4): 304-313 [Abstract] ( 3430 ) [HTML 1KB] [ PDF 1347KB] ( 298 )
314 Acknowledgements to reviewers
2016 Vol. 24 (4): 314-314 [Abstract] ( 1497 ) [HTML 1KB] [ PDF 91KB] ( 183 )
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