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Unsteady flows resulting from time-dependent inflow and variable aerator speed in a full-scale oxidation ditch and implications on residence time are explored via computational fluid dynamics (CFD). Flow in the ditch is driven (forced) by one inflow and two surface aerators. It is found that varying aerator speed is the primary factor inducing unsteady flow dynamics in the ditch while the time-dependent inflow induces negligible unsteady effects. In order to avoid expensive unsteady flow calculations, residence time analysis is performed for several steady flow simulations representative of the various stages during aerator operation. Significant differences between the mean residence time computed in the cases simulated suggests that unsteady flow dynamics throughout the operational cycle may have a significant impact on residence time characteristics in the ditch. Traditionally, residence time analysis is conducted based on a single steady flow representative of the average flow throughout the operation cycle of the system. Instead, following the results obtained here, it is recommended that residence time analysis be conducted under unsteady flow conditions or be based on a series of steady flow simulations each representative of the various operational stages of the system, in order to obtain a more realistic prediction of the hydraulic efficiency.

Based on the characteristics of the head checks (HCs) in curve rail of a heavy-haul railway, the design method for lower rail profile where the HCs occurred frequently by the cubic interpolation spline curve was presented. The algorithm including control points and the key control parameters in the profile, equations of the curve between adjacent control points and the boundary conditions were discussed. The control parameters was researched by applying the designed profile to a vehicle-track model for simulation of wheel-rail contact patch area and contact stress, wheel-rail lateral force and contact position in the rail. Results show that for curve radius below 800 m, the designed 75 kg/m rail profiles which lower profile from rail center to gauge side can make the acreage area of contact patch over 100 mm2 and both contact stress and lateral force smaller when the maximum lower amount of 0.1–0.6 mm, the maximum lowering position of 26–30 mm, the start point position 5–8 mm away from rail center.

To understand the characteristics of head check (HC) propagation, the methods for reconstruction and modelling HCs in the rail were presented by realizing the geometry morphology and spatial position of HCs with the help of some creative technologies: X-ray computed tomography (CT) was applied to detect the rail specimens taken from a curve in a heavy-haul railway and the three dimensional (3D) internal information of HC was extracted and digitalized to the point cloud data with 3D coordinate by thresholding of the grey level. For splicing HCs in different rail specimens, removing the abnormal points, extracting and fitting the edges of HCs, the algorithms for investigating the geometry characteristics, including geometry morphology and spatial angle were designed and programmed. Therefore, the reconstruction of 3D HCs in rail was realized by reconfiguration of geometry morphology and spatial position. By defining the contact property, the fitted 3D HCs were assembled and coupled with a 3D rail model for further crack propagation analysis with the eXtended finite element method (XFEM). The reconstruction results can provide an accurate method for reconstruct HC and a reliable model for study the HCs propagation in the rails of the heavy-haul railway.

Locomotive scheduling and train scheduling are important parts of the railway operation planning, locomotive scheduling should be cooperated with train scheduling, which could be benefit railroad operation efficiency and make railroad operation be more productive. This paper discuss the Cooperation design for locomotive scheduling and train scheduling based on Train Working Diagram System (TWDS). First, analyzing the business work flow between locomotive scheduling and train scheduling, and coordination process in TWDS. Then, according to the data flow and business requirements, design the mode of data sharing and data synchronizing. Finally, cooperation function and cooperation mode were designed for functions cooperation between locomotive scheduling and train scheduling.

The three dimensional (3D) point cloud model and its 2D cross section profile of a 60kg/m rail were obtained by a 3D scanner. But, it’s inaccurate to calculate rail wear with the 2D cross section profile directly which may has a certain inclination along the vertical center line of the rail because the 2D profile was sampled from the random point cloud. The algorithms for aligning the extracted profile from the 3D point cloud model by rotating the field side rail web curve, and parallel shifting the same side rail base line was presented. The results show a good effect comparing the standard profile with the precision less than 0.1mm. Detail implementation of the algorithm was put forward by MATLAB and its feasibility and stability were verified. INSTRUCTION Wear is one of the major types of rail defects. With the increase of train speed, axle load and traffic density, the rail wear is more serious, which leads to the great rail profile changes, thereby affecting the performance of vehicle operation and dynamic forces between wheel and rail. Therefore, measuring the rail head profile, calculating the rail’s vertical and lateral wear accurately are important to the railway safety and economical operations (Telliskivi T, Olofsson U. (2004)). At present, there has been numerous research on measuring rail transverse profile and calculating rail wear, such as mechanical fixture contact measurement, laser non-contact measurement, and mechanical contact electrical measuring and so on. A Rail profile drawing device, P110B, has been developed by VOGEL&PLOTSCHER, and its precision can achieve 0.5mm. Die NextSense Mess-und Prufsysteme GmbH developed the equipment known as Calipri that records rail profile by laser technology, then calculates the rail wear automatically. MiniProf developed by Green Wood in Denmark is a portable rail profile measurement device which can measure the whole rail head profile. Data processing algorithms for rail wear calculation have been realized including radius

A floating slab track is applied in urban rail transit for vibration reduction. However, under repeated vehicle loads, stress concentration might occur to fixed bolts in the shear hinge of a slab. To investigate the stress and deformation distribution and locate the maximum stress on bolts, a two-dimensional (2D) floating slab track model and a three-dimensional (3D) bolt-shear hinge-slab model were established to analyze the distribution of stress and deformation. The results showed that stress concentration was located in the upper part of the bolt. Stress in the upper part of the bolt and bolt head was much higher than in rest of the parts. Stress in the bolts that were close to the end of the slab was higher than that in others, and it could be reduced by 20% when adding one bolt and by 12% when moving bolts 0.25 unit length towards to the end of slab. Bolt pre-tightening force could significantly affect stress distribution.

In the modern design codes adopting load and resistance factor design (LRFD), the resistance factors for various models for the design of geotechnical systems were calibrated with the load factors that had been determined by structural engineers. Although the consistent performance or risk level was intended for LRFD, the uncertainty remains in the geotechnical design obtained with LRFD, as the variability of input parameters at a given site could be quite different from those variation levels assumed in the calibration of resistance factors. Thus, the question of how likely the completed geotechnical system meets the performance requirement does not vanish even with LRFD. A logical question then is “how can we perform LRFD so that the geotechnical system will remain feasible (i.e., being able to satisfy the performance requirement) in the face of uncertainties.” In this paper, we proposed an approach that integrates the robust design concept with LRFD, termed robust LRFD (R-LRFD) approach, to help solve this problem. We demonstrated this R-LRFD approach with a drilled shaft design example documented in ETC10. Comparison was made between the LRFD solution with that obtained using the proposed R-LRFD approach.

Express freight transportation plays an important role in railway transportation, and express freight train diagram is the integrated plan for railway freight transportation. This paper discusses the coordinating methodology during express freight train scheduling process. Base on analyzing the procedure of railway transportation plan and relation to other railway operation plan or technical work, the coordination between express freight train scheduling and railway station operation, passenger train plan, maintenance time window plan and locomotive scheduling were considered, some proposed methods were put forward to optimized the express freight train diagram, which would benefit the quality and robustness for express freight train. With the development of national economy, adjustment of industry structure and productivity layout, improvement of consumption level, express freight transportation demands increased rapidly. Moreover, customers need higher requirements for rapidity, punctuality, convenience, safety of freight transportation to railway companies. Therefore, express freight transportation has become an important part of freight transportation market. Express freight train diagram is the integrated plan for railway freight transportation, based on train plan, express freight train diagram defines many parts such as train class, departure and arrive station, goods category, running cycle routing and etc. And then, train lines are drawn according to running speed, outgoing time or terminate time, service and technical operations. Reliability and accuracy are the important and direct indicators to measure the level and quality of service for train diagram. Express freight trains consist of regular freight train and direct freight trains. During the process of express freight train scheduling, not only rail passing capacity and train plan, but conditions of other equipment and constraints for technical operations were took into account. This paper discusses the coordination between express freight train scheduling and railway station operation, passenger train plan, maintenance time window plan and locomotive scheduling.

Research on aerodynamic performance of high-speed trains in cutting with different slope angles would complement the operation safety management under strong winds. This study was conducted to investigate the flow structure around train using computational fluid dynamics (CFD). The accuracy of the numerical method was validated, combined with wind tunnel test. This work shows that the surroundings of cutting along the railway line have great effect on the crosswind stability of train. With the increase of slope angle , the coefficients of aerodynamic forces tend to reduce. Comparing the angle 0° with 90°, the Cs, Cl and Cm of head car fall by 96.7%, 108%, and 96.8% to the maximum respectively, while those of middle car by 108%, 98.8%, and 105%. For the shield of applicable cutting, the whole body is in a minor positive pressure environment. Thus, an appropriate slope angle for the cutting can largely improve its windbreak performance.

With the complex conditions in urban rail transit, the rail in continual welded rail (CWR) may be broken in some sections. Track circuits in a traditional signal system can find the broken rail when this damage happens. However, after a state-of-the-art signal system — such as the Communication-Based Train Control System (CBTC) — was applied, the role of the track circuits disappeared. In this paper, the existing broken rail detection methods and technology were summarized. A monitoring system of broken rail for urban rail transit based on ultrasonic guided waves was proposed combined with automatic data collection and transmission technology. Considering the overall system, the level and frame structure of the system was analyzed. Moreover, the signal frequency of ultrasonic guided wave, the type and location of broken rail, and the data transmission methods were discussed. A large number of laboratory tests was carried on to determine different calibration conditions.

Track components —such as rail, fastening, and ballastless slab — in urban rail transit are damaged frequently by train dynamic load or temperature and humidity of the environment around the track. Traditional inspection methods, like human inspection and identification, were low in efficiency and high in missing rate. In this paper, based on the theory of Image Recognition (IR), the identification algorithm for track components' condition and damages was researched. The image processing method, the identification operators and data transform method were analyzed. The image recognition method for track component damages was presented. The broken rail and crack in rail food from the photo graphics by inspection were recognized and identified. It shows this method has high accuracy and identification capability. It will be the key technology for the software of high-speed photograph technology and image recognition technology in the inspection of the track components in urban rail transit.

Electric multiple units (EMU) train traction calculating is a basic part of high-speed railway operation and design. To study and develop EMU trains traction calculating system is important for high-speed railway train operation and design efficiency. This paper, based on the business needs, thoroughly carries out analysis and design to the EMU train traction calculation system and focuses on exploring the calculation model of the EMU train traction calculating, EMU manipulation strategies, EMU over-phase calculation, and other problems; puts forward a single particle simplified calculation model; puts forward a combined simplified model of a single-particle model and a multi-particle; and finally develops a prototype system of EMU trains traction calculating system.

Special conditions in coal mines have led miners to determine that water is the best purging medium in sub-horizontal drilling construction. However, water caused many inconveniences in water-sensitive formations which often appear in gas holes. In response to the identified problem, this paper provides several solutions and illustrates how to execute different methods according to different conditions and cases.

On the basis of monitoring requirements and field conditions of urban rail transit, an automatic real-time monitoring system for measuring wheel/rail dynamic response was researched. The architecture and components of it was analyzed with the guide of Internet of Thing (IOT) theory. Moreover, the automatic control technology and communication network technology such as 3G and VPN were applied in the system. The data of wheel/rail dynamic force, displacement and vibration acceleration of track components caused by passing trains were measured, collected, processed and transmitted automatically in real time. The results from laboratory and field tests show the system can measure track dynamic response, analyze and transmit the data automatically according to trigger signal of passing trains. The function of real-time and unattended monitoring for track conditions was realized. With the development of urban rail transit to network construction and operation, large train formation, high traffic density, the load acting on the track structure and its components gets higher, which will accelerate the deterioration of track structure, increase vibration and noise and reduce the lifetime of track components. It is important to know the real-time track condition under this load environment for rational track maintenance. The track condition can be reflected by track dynamic response caused by train passing such as wheel/rail dynamic force, displacement and vibration acceleration of track components, which have close relationship with vehicle-track dynamic interaction. The measurement for this kind of parameter usually uses instrumented wheelset on vehicle or field test along track side. The former needs a special instrumented wheelset installed instead of one normal wheelset to the normal vehicle or specially designed vehicle. Its components and devices are complex and the cost for operation and maintenance of it is high. It is generally used as regular inspection instead of continuous monitoring. The track condition between two inspections cannot be obtained unless shortening the inspection interval which will affect the normal train operation. The latter set several test point along track side and can be carried on as continues monitoring. But it needs manual operation and enough space beside tracks for devices and operation persons. This will limit the long period

In the real large space fire, non-uniform longitudinal and transverse temperature distributions were usually occurred by fire position. Using finite element analysis software ANSYS, maximum deflection of a fixed supported steel beam with three aspects surrounding fire was analysed in this paper, it supposed non-uniform transverse temperature distributions on the basis of non-uniform longitudinal temperature distributions which was assumed firstly, and also made comparisions with uniform longitudinal temperature distributions. © 2012 ASCE.

In this paper, through designing objects such as a ball, coconut and bricks, and the vehicle front windshield glass collision experiment, data of the front windshield glass rupture area and the collision object quality and speed is collected. The regression function of the rupture area and speed quality relation is given. The actual traffic accident case is used to validate the functional reliability. The paper will provide a new method for vehicle speed determination in a traffic accident, which has a very important reference significance.

Crew scheduling is one of important part of transportation operating organization of passenger dedicated line, and the crew plan is the key process during crew scheduling. On the basis of analyzing the possible plan forms when cycle was designated, considering the scheduling to be easily programmed and practiced, this paper establishes crew scheduling model and a similarly greedy algorithm was designed to solve the problem. An example shows that it is feasible to schedule a crew rostering plan in condition of cycle by using this algorithm.

In recent 10 years, several accident cases and theories showed that soil distribution around the shield tunnel has direct or indirect impact on the failure models of tunnel segment structure. In this paper, a 1:38.75 ration physical model test is developed and carried out to clarify the impact of the soil variation on the mechanical behaviors of the tunnel segment structure. Some conclusions are put forward that soil variation does have an influence on the structure, but with different grades in different places of the segment structure. The value of displacement, bending moment of the segment structure located in the variation area increase dramatically, and the extremum points move to side of the varied soil in the structure. However, the structure located in the unvaried region remains almost the same status as that in the green field.

The paper investigates the applicability of IRI-based pavement deterioration prediction models, which include four deterministic models for pavement performance prediction (i.e., the NCHRP model, Al-Omari-Darter model, Dubai model, and the NMDOT model used by the New Mexico Department of Transportation). Comparisons of these models are made using the data from both the NMDOT Pavement Management System (PMS) and the Long-Term Pavement Performance (LTPP) sites in New Mexico. It is found that the NCHRP and the Dubai models are relatively good tools for pavement performance prediction in New Mexico, while the Al-Omari-Darter model and the NMDOT model do not provide a sound statistical basis. In addition, one probabilistic model for pavement service life prediction, i.e., the survival curve, is also presented. The service life estimated by survival curve is compared with those determined from two approaches — pavement age and traffic loading. The result of traffic loading approach is found to be more reasonable.

LOSS (Level of Service of Safety) is used to weigh the quality of safe operation that roads provide to the drivers and other traffic participants. Reasonable speed limit not only controls the speed of vehicles in appropriate range on the road, but also guarantees the traffic safety of the road. Crash rate was selected as a quantitative indicator, hierarchical standard of LOSS for freeway and arterial highway was studied, and then the LOSSs of freeway and arterial highway in China were divided into 4 levels. In virtue of the probability statistics, robust regression and on the basis of accident data, speed limit and geometric factors the accident prediction models were established. Based on the acceptable LOSS the method of setting speed limits about cars and trucks respectively was formed. The results would help traffic engineers in Chinese highway management departments choose right speed limits for freeway and arterial highway.

From the perspective of regional logistics system planning and based on the existing method of logistics center location; this paper proposes a concept of location model of regional logistics center in reference to accessibility. Under the constraints of transportation network, geographical conditions and other factors and through the analysis of regional accessibility, this paper constructed a location model of logistics center considering the accessibility and coverage in the regional transport network, and other indicators. Finally, combined with a practical example, the paper also proves the practical application value of this model.

With the development of economy and the improvement of living standards, the vehicles in public places are increasing. In today's world, the traditional technology of parking management can not satisfy the needs. This paper aims to improve the efficiency of vehicles management and guarantee the safety of vehicles. The research paper presents an intelligent vehicle management expert system with radio frequency identification (RFID) technology. The system provides practically important user data collection, guidance information, control information and can trace criminal or illegal vehicles such as stolen cars or vehicles that evade tickets, tolls or vehicle taxes. The system architecture consists of an RFID reader, a passive tag, a terminal computer, a pair of magnetic induction coils and a high-speed server with a database system. The system collects user information and allocates parking spaces on a community of a district area in a city based on RFID technology. Moreover, it can identify cars that do not have a tag and then provide a temporary card through Automatic Vending Machine.

From the new perspective of urban traffic efficiency and low carbon transportation systems, this paper discusses and summarizes the interactive relationship between urban land use patterns and transportation system. A comprehensive model is designed based on minimum travel time concerning both the optimization of land use around high speed railway station and the optimization of population under restriction of a certain land use and population condition. A case study from the city of Yixing, which is located on the railway line between Nanjing and Hangzhou will research the high speed railway’s effects on the land use around the railway station. Results from the study show that the application of this model is simpler, more practical, and highly operational, when compared with the traditional planning methods. Finally, this paper will develop land use strategy, which provides theoretical foundation and methodology for the planning and construction of sustainable cities with high speed railway stations.

The study on speed-flow models of arterial roads is very important in traffic flow theory. In this paper, we improved the available models based on studying speed-flow models at the international level. We compared the differences and conducted an experimental study with real data. The main innovations with the comparative analysis include 1) fitting the curves on the basis of an improved Highway Capacity Manual (HCM) model, 2) identifying the identical and different features of different links connecting intersections based on the speed-flow model, and 3) conducting a comparative study of some special characteristics of speed-flow relationship. According to this study, more can be learned about the traffic status of the arterial roads in Beijing, and useful suggestions to improve Beijing’s traffic situation are made.

Countdown signal can be used to remind drivers when the colors of signal change and help them choose appropriate driving behavior to go through an intersection between stoppings and crossings. It is a method to reduce complexity of judgments for drivers when the colors of a signal change. In China, the study on the effects of countdown signal at intersections on drivers’ violating behavior is few. From the results of the investigative questionnaire, more than 85% of drivers and pedestrians preferred countdown signal to no-countdown signal. More than 85% of drivers and pedestrians thought the intersection with countdown signal was safer than the intersection with no-countdown signal. The paper will be researched on an intersection with four legs in Beijing fangzhuang district in the virtue of video recorders. It analyzed the drivers’ behavior during seven days before and after installing the countdown signal respectively, which was digit-display countdown timing and showed the whole green and red time. The findings indicated that traffic volumes were quite similar before and after installing the countdown signal, however, the drivers’ behavior of yellow-crossing and red-running decreased significantly after installing the countdown signal.

This study analyzed the relationships between alignment elements and traffic accidents, traffic flow characteristics and traffic accidents, and environmental features and traffic accidents, which were based on the presumption that drivers on the freeway had better conditions for steering and had experience driving. The findings from the freeway Jing Jintang in plain terrain is that the ideal alignment design is not a main factor causing traffic accidents. There are strong and obvious correlations between traffic flow characteristics and traffic accidents and environmental features and traffic accidents. By means of nonlinear regression, the crash rates prediction models were constructed, the dependent variables are crash rates including three types which are: property damage only accident rate, casualty accident rate and the total accident rate. The independent variables are the characteristics of traffic flow and the environment. The three models can be used as management tools for traffic engineers to measure the safety of freeways.

Foamed asphalt treated mixture is a kind of material whose properties are between semi-rigid and flexible. However, there is not enough information of strength characteristics of this material for the authors. In this study, the authors monitored the foamed asphalt treated mixture’s characteristics of strength, density and moisture content with different curing conditions to study the formation process and regularity of it’s strength character. The authors investigated the relationship between strength forming and asphalt dispersion with the help of micro-scale analysis observations and it was found that in the study that obtained strength factors for foamed asphalt mixture was directly related to the evaporation of water and there was a migration process for asphalt. In this process, asphalt blocked some of the void of test specimen, so that the opening voids decreased and the closed void increased instead. As a result, water stability of foamed asphalt concrete was improved.

Highway capacity is the basic standard of highway construction and management. It is defined as the maximum volume of traffic flow through a particular highway section under given traffic conditions, road conditions, and so on. In order to explore the highway capacity model under complicated roadway characteristics, this paper establishes a practical model based on one month of serial data collected from loop detectors at different sites on the expressway in Beijing. On the basis of different road conditions, we classify the expressway into different types. Based on the gap acceptance theory, the authors establish a model for each kind of road and give the recommended capacity value separately.

In reservoir areas, due to the change of water environment, the properties of rock/soil change. Therefore, it is necessary to study the changed rock/soil properties due to watering and develop necessary forecasting models. In this study, saturation experiments were performed in the laboratory using rock/soil samples from a bank-slope located in the Three Gorges Reservoir and water samples from the Yangtze River. By SEM (Scanning Electron Microscope) analysis, the mini-structures of undisturbed samples were studied. It shows that the mini-structure of rock/soil changes after a 9-day saturation period in flowing water. Before saturation, the soil structure was of good integration and mainly composed of piled and accumulated prothallus. After saturation, the structure changes to be flocculent and there are many scattered prothallus which connect to each other mainly by edges and angularities. Compare to the unsaturated samples, there are more pores in the saturated samples caused by corrosion.

Accurate assessment of pavement performance life is the cornerstone of pavement management system. During the last decades, many pavement life expectancy models relying on various concepts from purely empirical to truly mechanistic have been developed. However, the lack of adequate systematic and efficient model classification system and analysis has been the major barrier for further research on pavement life expectancy. This paper performs an in-depth review on flexible pavement life prediction models and addresses a new model classification method that can facilitate the model-selection for pavement engineers.