T-shaped Intersection Research Articles

CFD simulation of indoor-outdoor wind-driven ventilation and traffic pollutant dispersion at a T-shaped street intersection (ISHVAC 2023)

Traffic exhaust is considered a predominant pollutant source for buildings along streets. However, there are few studies on ventilation and pollution dispersion inside buildings and along streets in a T-shaped intersection. This study investigates the ventilation performance and pollutant dispersion inside and outside multi-unit buildings at T-shaped intersections in different wind directions. Different wind-driven ventilation modes have been compared, i.e. SS2 (single-sided ventilation with 2 openings) and CV (cross ventilation). The results show that multi-unit buildings have the potential to enhance SS2 ventilation performance. The diffusion of outdoor pollutants into indoor environments is more closely related to wind direction for SS2 than CV. However, at certain wind directions (θ = 135°), a significant increase in indoor pollutant concentrations is observed in CV, nearly tenfold higher than that in SS2 cases. The findings could contribute to the understanding of ventilation in multi-unit buildings at T-shaped street intersections.

Implementation of a hybrid method for optimizing traffic light phases using Anylogic

Traffic light interval signals have been operating according to the same pattern for many years. Small towns do not create traffic control units due to high costs. The operation of a traffic light is limited to several modes or has constant values of the temporary duration of traffic light phases throughout the day, which makes it difficult to organize traffic during times of high traffic loads on the road network. An algorithm is proposed for optimizing the traffic light phases of traffic flows at a T-shaped intersection depending on the traffic load on the network, which changes during the day. The effectiveness of the proposed algorithm is demonstrated by numerical experiment.

Shaking table tests on the seismic performance of prefabricated T-shaped cross utility tunnel

The seismic performance of the intersection of a T-shaped cross utility tunnel is weak under earthquake excitation. This study is the first to perform 1/20 scaled shaking table tests on the seismic performance of prefabricated T-shaped cross utility tunnel based on an actual utility tunnel project. Micro-concrete was used to create prefabricated utility tunnel models, and a prefabricated T-shaped cross utility tunnel was assembled by a T-shaped intersection and prefabricated utility tunnel segments using bolts. The laminar shear model box was used in the tests, and earthquake excitations along the two principal axes of the prefabricated T-shaped cross utility tunnel were inputted respectively at the bottom of shear box. The model soil acceleration, prefabricated utility tunnel strains, and opening and dislocation of joints were tested and analysed. Numerical simulation was conducted on the test cases, the test and numerical results were in good agreement. The results showed that the significant strain concentration on the T-shaped intersection or its adjacent utility tunnel was found under earthquake excitations along the two principal axes of the T-shaped utility tunnel, owing to incompatible deformation caused by the difference in lateral stiffness between two intersecting utility tunnels. The amplification of the axial strain at the T-shaped intersection or its adjacent utility was up to 5.2–6.4 times. Under earthquake excitations along the two principal axes of the T-shaped utility tunnel, the significant opening or dislocation of joint between the T-shaped intersection and prefabricated utility tunnel was found. The closer the joint was to the T-shaped intersection, the larger the opening or dislocation of joint. The amplification of the dislocation or opening of joint between the T-shaped intersection and prefabricated utility tunnel was 5.7–10 times. This study provides a certain reference for the seismic design of T-shaped cross utility tunnel.

Experimental and numerical study of T-shaped irregularly concrete-filled steel tube columns under combined axial loads and moments

T-shaped irregularly concrete-filled steel tube column (T-ICFSTC) is formed by I-shaped steel, U-shaped steel and infilled concrete. The I-shaped steel and U-shaped steel are welded together to form a multi-cell CFST column. The T-ICFSTCs can be used in the corner of T-shaped intersection location of two walls in the buildings, which can avoid the exposure of the columns and increase the available area of the indoor space. The overall flexural stability performance of the T-ICFSTCs under axial loads and moments may still be an important problem in engineering design. This paper studies the overall flexural stability performance of the T-ICFSTCs under combined axial loads and moments. Firstly, the experiments of two T-ICFSTC specimens under eccentric loading with eccentric distance of 100 mm and opposite eccentric directions were carried out. Subsequently, the refined finite element (FE) models and the simplified finite element (FE) models are established and verified by the experimental results. The simplified FE models use beam elements (B31) and have higher calculation efficiency than the refined FE models, and are adopted for the numerical investigation of the T-ICFSTCs. Finally, based on the simplified FE model verified by the experimental results, the parametric analysis of the overall flexural stability capacity of the T-ICFSTCs under axial loads and unidirectional moments is carried out. The parameters studied include the height of the T-ICFSTCs, several geometric parameters of the cross section and the strength of material. Based on the results of numerical investigations, a preliminary design formula of the overall flexural stability capacity of the T-ICFSTCs under axial loads and unidirectional moments is proposed. This paper provides reference for engineering design of the T-ICFSTCs and the foundation to establish a complete design formula of the T-ICFSTCs under axial loads and unidirectional moments.

High-order discontinuous Galerkin approximation for a three-phase incompressible Navier–Stokes/Cahn–Hilliard model

In this work we introduce the development of a three-phase incompressible Navier–Stokes/Cahn–Hilliard numerical method to simulate three-phase flows, present in many industrial operations. The numerical method is then applied to successfully solve oil transport problems, such as those found in the oil and gas industry. The three-phase model adopted in this work is a Cahn–Hilliard diffuse interface model, which was derived by Boyer and Lapuerta (2006). The Cahn–Hilliard model is coupled to the kinetic-energy stable incompressible Navier–Stokes equations model derived by Manzanero et al. (2020). The spatial discretization uses a high-order discontinuous Galerkin spectral element method which yields highly accurate results in arbitrary geometries. An implicit–explicit (IMEX) method is adopted as temporal scheme for the Cahn–Hilliard equation, while Runge–Kutta 3 (RK3) is used for the Navier–Stokes equations. The developed numerical tool is validated with a manufactured solution test case and used to simulate multiphase flows in pipes, including and a three-phase T-shaped pipe intersection.

ENGINEERING AND PLANNING SOLUTIONS OF BUS STOPS OF TRANSPORT ON THE EXAMPLE OF KYIV

The purpose of the study is to conduct an analysis of foreign and domestic experience regarding planning decisions of bus stops and to identify their influence on the formation of transport interchanges. The article presents the generalized results of the current state of engineering and planning decisions of bus stops in the city of Kyiv and reveals the factors of influence of spatial planning decisions on the formation of transport and transfer nodes in the urban environment. The areas of improvement and development of the functional-spatial organization of solid waste are considered. The article is aware of its purpose, namely, it presents the generalized results of the state of planning decisions of bus stops in the city of Kyiv, determines the influencing factors on the formation of transport interchanges. Analysis of the current development of bus stop planning solutions in the capital made it possible to form a classification and distinguish types of bus stops according to four classification features: functions, volume of passenger traffic, location of bus stops, and degree of modality. The study of the spatial configuration of solid waste on the basis of bus stops made it possible to identify the following types of solid waste: the solid waste zone is located at an intersection; the solid waste zone is formed at a T-shaped intersection; the solid waste zone, which consists of stopping points, placed sequentially; solid waste zone, which contains stopping points located in parallel; combined type of solid waste. The analysis and research of the current engineering and planning solutions of bus stops in the city of Kyiv revealed that the formation of solid waste in the urban environment mainly takes place on the basis of railway stations, airports, bus stations, which receive and send external passenger flows directed in city.

АВТОМАТИЗИРОВАННАЯ ТРАНСПОРТНО-ТЕХНОЛОГИЧЕСКАЯ СИСТЕМА ОРГАНИЗАЦИИ ДОРОЖНОГО ДВИЖЕНИЯ И СОЗДАНИЯ ТРАНСПОРТНЫХ КОРИДОРОВ

There is considered a problem of road traffic organization at crossroads under conditions of urban environment and outgoing highways. The urgency of the problem of automated traffic control with the information for vehicle drivers about traffic situation using both navigation systems and warning systems by means of signal transfer to radar-detectors is shown. 
 The investigation purpose consists in the development of automated self-regulated system of traffic lights control on the basis of vehicle number approaching to the traffic lights and vehicle driver warning about traffic jam approaching for the purpose of its going around. 
 In the paper there are solved problems regarding traffic capacity of a megapolis traffic system, driver warning about problem road situations and the automation of these processes. On the basis of the theory of automated control there is shown a developed system allowing the formation of a traffic passage by means of driver warning about traffic jam ahead. There are described thoroughly component parts of the system limiting only with the choice of components among prototypes available in the market. 
 A principle of automated traffic flow control at the crossroads supplied with the traffic lights is shown. There is shown a functional diagram of the interaction of system components for the successful traffic organization. The algorithm of the system automation functioning with its adjustment to certain time intervals of the effect of the enabling traffic light signal at a particular T-shaped or X-shaped intersection is described. The system developed for traffic control at intersections allows relieving considerably city streets. The analysis of the system has shown that traffic lights adaptive control allows decreasing traffic up to 70%. The application of domestic software components decreases system cost by 2-4 times as compared with foreign prototypes which, among other things, do not have the functional offered.

ПОВЫШЕНИЕ БЕЗОПАСНОСТИНА НЕРЕГУЛИРУЕМЫХ ПЕРЕКРЕСТКАХ АВТОМОБИЛЬНЫХ ДОРОГ

The article presents the results of studies of the organization of traffic at the T-shaped intersection of regional highways: highway 60K-245 - highway 60K-12, connecting the village of Kamenolomni with the city of Novocherkassk, Rostov region. The research is based on the conducted field survey of traffic intensity. As a result, a conditional cartogram of the traffic intensity of vehicles was developed, an analysis of conflict points at the intersection was carried out, and traffic light graphs were calculated for the current traffic intensity of traffic flows.

Mechanical Properties of Rock With Intersection Structures and its Progressive Failure Mechanism

To investigate the influence of intersection structures on the mechanical properties and failure mechanisms of rock materials, a series of uniaxial compression tests on complete red sandstone specimens and specimens with various hole shapes (T-shape, cross-shape, and shaft-roadway-shape) were conducted by the Instron 1346 servo-controlled rock mechanics testing machine. Flac3D software and digital image correlation (DIC) were used to simulate the internal stress distribution of rock specimens and reproduce the process of fracture, i.e., cracks initiate, propagate, and coalesce with each other into macroscopic failure under progressive loading. The results show that the intersection structure has a significant weakening effect on the mechanical properties of the rock. The rock strength, elastic modulus, and peak strain of specimens can be ranked as complete specimens > cross-shaped intersection structure specimens > T-shaped intersection structure specimens > shaft-roadway-shaped intersection structure specimens. The energy consumption ratio of the intersection structure specimens before the peak reaches more than 30%, which is approximately twice that of the intact specimens. The brittleness coefficients of the four types of specimens are 0.18, 0.26, 0.21, and 0.20, respectively. The intersection structure specimens induced different degrees of tensile and compressive stress concentration zones on the top and bottom sides of the intersection center point. As a result, initial tensile cracks parallel to the loading direction and shear cracks leading to spalling failure on both sides of the holes were formed. With the increase of the axial stress, secondary tensile cracks extending on the opposite direction appeared at the upper and lower corners of the hole. When the far-field cracks that propagated along the diagonal line coalesced with secondary tensile cracks, macro shear-failure of the specimens appeared. With the increase in axial stress, the principal strain monitored during the fracture process of the specimens gradually increased, then it slowly decreased after the peak. The arched boundary of the T-shaped intersection structure specimen had good stability because of its advantage of suppressing the occurrence of the spalling failure. The shaft-roadway-shaped intersection structure could provide compensation space for the secondary tensile cracks due to the existence of the vertical well. The degree of inhibition of initial tensile cracks was so small that the type of specimens was highly prone to instability or failure.

Dynamic characteristics of traffic flow with consideration of crossing pedestrians’ behavior at a nonsignalized T-shaped intersection

In this paper, we present a cellular automata model to depict the traffic characteristics at such a nonsignalized [Formula: see text]-shaped intersection in the presence of pedestrian crossings. The vehicular traffic flow characteristics with different parameters are studied. Throughput, phase diagrams, space-time and density profiles are built to point various traffic states and the phase transition features. The principal finding of the simulation are as follows: (1) The presence of crossing pedestrians has a significant influence on the vehicular traffic and the system performance, (2) The intersection capacity has a close relevance with the state of the weaving section. The smaller the interactions are at the weaving section, the higher the capacity and (3) In order to have a higher system ability, the crosswalk location should not be far from the yield line of the weaving section.

Retraction Note to: Numerical simulation on pollutant dispersion from vehicle exhaust in street configurations.

The impact of the street configurations on pollutants dispersion from vehicles exhausts within urban canyons was numerically investigated using a computational fluid dynamics (CFD) model. Three-dimensional flow and dispersion of gaseous pollutants were modeled using standard κ − e turbulence model, which was numerically solved based on Reynolds-averaged Navier–Stokes equations by the commercial CFD code FLUENT. The concentration fields in the urban canyons were examined in three cases of street configurations: (1) a regular-shaped intersection, (2) a T-shaped intersection and (3) a Skew-shaped crossing intersection. Vehicle emissions were simulated as double line sources along the street. The numerical model was validated against wind tunnel results in order to optimize the turbulence model. Numerical predictions agreed reasonably well with wind tunnel results. The results obtained indicate that the mean horizontal velocity was very small in the center near the lower region of street canyon. The lowest turbulent kinetic energy was found at the separation and reattachment points associated with the corner of the down part of the upwind and downwind buildings in the street canyon. The pollutant concentration at the upwind side in the regular-shaped street intersection was higher than that in the T-shaped and Skew-shaped street intersections. Moreover, the results reveal that the street intersections are important factors to predict the flow patterns and pollutant dispersion in street canyon.

Phase diagram of a non-signalized T-shaped intersection

In this paper, we investigated a non-signalized T-shaped intersection using the cellular automata model under the open boundary condition. Two different priority rules at intersection are introduced (Rule 1, Rule 2) to eliminate the jam-packed state. Phase diagram and its variation with the ratios of right and/or left turning vehicles are investigated. The space-time and the density profiles are also studied. The simulation results indicate that the system does not show the same performance under different priority rules, where Rule 1 (resp. Rule 2) can be better than Rule 2 (resp. Rule 1) according to the ratios of turning vehicles.

Cellular automaton simulations of a T-shaped unsignalised intersection with refined configurations

This article investigates traffic flow at a T-shaped unsignalised intersection based on the cellular automaton (CA) simulation. This approach can reveal many microscopic features of traffic flow. We used a refined Nagel–Schreckenberg model and the geometry of the intersection has been considered, in which vehicles are assumed to move along 1/4 circle arcs in the intersection. Yield rules need to be obeyed when conflict occurs. Three-dimensional (3D) visualisations have been created with the support of an OpenGL, which gives more user-friendly and realistic presentations. We have presented the diagrams of intersection states and studied the capacities of different approaches. Our method is expected to become a general approach for CA simulation of intersections.

Deflecting-Obstacle Effects on Signal Propagation in the 60 GHz Band

This paper reports the non-line-of-sight (NLOS) results of broadband measurements and modeling of signal propagation characteristics in the 60 GHz band. The purpose of this work was to evaluate the importance of the presence of deflecting obstacles (DOs) for indoor wireless local area network (WLAN) applications in the unlicensed 60 GHz band. Based on sweeping-frequency sounding technique (59.6-60.6 GHz), an indoor propagation measurement campaign was carried out in a typical T-shaped intersection of two long corridors under non-line-of-sight (NLOS) at a distance of 20 meters between transmit and receive antennas, with and without the presence of DOs. Based on Ray-Tracing (RT) technique, deterministic models are derived for the considered environment. An interesting agreement is achieved between the predicted and the experimental results in both frequency and time domains. Thus, this work demonstrates that mm-waves communications are very sensitive to the propagation environment as compared with lower frequency bands. In NLOS corridor environments, the signal transmission relies mainly on the unavoidable diffraction phenomenon from the intersection corners. However, the presence of a DO might overcome significantly the hostile propagation characteristics that are normally encountered under NLOS propagation conditions.

Characteristics of Traffic Flow at Nonsignalized T-Shaped Intersection with U-Turn Movements

Most nonsignalized T-shaped intersections permit U-turn movements, which make the traffic conditions of intersection complex. In this paper, a new cellular automaton (CA) model is proposed to characterize the traffic flow at the intersection of this type. In present CA model, new rules are designed to avoid the conflicts among different directional vehicles and eliminate the gridlock. Two kinds of performance measures (i.e., flux and average control delay) for intersection are compared. The impacts of U-turn movements are analyzed under different initial conditions. Simulation results demonstrate that (i) the average control delay is more practical than flux in measuring the performance of intersection, (ii) U-turn movements increase the range and degree of high congestion, and (iii) U-turn movements on the different direction of main road have asymmetrical influences on the traffic conditions of intersection.

Coherence bandwidth measurement in indoor broadband propagation channel at unlicensed 60 GHz band

Reported are the results of a coherence bandwidth experimental investigation of broadband propagation measurements for future millimetre-wave WLANs. Based on a sweeping-frequency sounding technique (59.6–60.6 GHz), the channel coherence bandwidth (Bc) is estimated in two typical indoor environments: (a) a 20 m, non-line-of-sight (NLOS) T-shaped corridors intersection, with and without the presence of a transmission route deflecting obstacle (DO), and (b) a line-of-sight (LOS) empty conference room. Results demonstrate thats millimetre-wave communications are very sensitive to the propagation environment. Thus, precise information of phases and amplitudes across the band of interest are essential for accurate estimation of the channel Bc. Results also indicate that the NLOS millimetre-wave environments are very hostile and the presence of DOs might enhance significantly the millimetre-wave propagation characteristics including the channel Bc.

Study on evacuation behaviors at a T-shaped intersection by a force-driving cellular automata model

A force-driving cellular automata model considering the social force on cell movement, such as the desirous willing of a pedestrian to exit, the repulsive interaction among pedestrians or between pedestrians and obstacles, was set up to investigate the evacuation behaviors of pedestrians at a T-shaped intersection. And an analogical formulation, taking reference of the magnetic force, was introduced to describe the above repulsive actions. Based on the model, the evacuation behaviors of pedestrians were simulated in terms of different pedestrian density, distribution and corridor width, and then evacuation time was obtained and analyzed. Furthermore, an experiment was conducted to verify the results of the presented model. The results demonstrate that when the density of pedestrians is greater than a certain threshold, pedestrians of a certain direction would be jammed by the repulsion from pedestrians of the counter flow from another direction, and the evacuation time of the former would be longer, even though they are closer to the exit, which would possibly result in a serious casualty in an emergency circumstance. And the phenomenon has been validated by the experiments well. In addition, a corresponding critical corridor width related to different DOPs, beyond which the evacuation time could be decreased rapidly due to a strong degradation of jamming behaviors near the T-shaped intersection, was also discovered and predicted by the proposed model.

TRAFFIC FLOW AT A SIGNAL CONTROLLED T-SHAPED INTERSECTION

In this paper, traffic flow at a signal controlled T-shaped intersection with three input roads is investigated by using the cellular automata model. When each road is a double lane, the model only exists in three conflict points among three directions of flows. We introduce three-phase traffic signal and two types of signal controlling strategies, i.e. fixed signal phase order as well as adaptive signal phase order strategy, to control the traffic flow at the intersection. The phase diagram, the capacity and the average travel time of the system are investigated and compared under both strategies. The simulation results show that the traffic adaptive signal strategy is better than the fixed signal phase order strategy.

COMPLETE TRAFFIC PATTERNS AROUND A T-SHAPED INTERSECTION

We propose Asymmetric Simple Exclusion Processes to analyze the traffic states around a T-shaped intersection. The system consists of six roadways connected by the intersection. There are nine control-parameters separated into three categories: injection αi, removal βi, and turning Pi, (where i = 1, 2, 3). As these nine parameters change, traffic states on each roadway reveal a two-phase transition: free flow (F) and jam (J). Together, there can be 64 (=26) possible combinations for the traffic phases. We observe 63 distinct phases. We analyze three major causes of congestion: (1) increase of traffic demand simulated by injection αi; (2) decrease of roadway capacity simulated by removal βi; (3) redistribution of traffic pattern simulated by turning Pi. In case (1), congestion can be confined to the roadways heading toward the intersection. In case (2), spillovers can be observed and congestion will pervade the whole system. In case (3), congestion can be triggered by both increasing Pi and decreasing Pi. The phase diagram can be a convenient tool to summarize the results of numerical simulations. We also compare the unsignalized intersection to an intersection regulated by traffic signals. We find that the operation of traffic signals is very inefficient in resolving the congestion around a T-shaped intersection.

CELLULAR AUTOMATA MODEL FOR UNSIGNALIZED T-SHAPED INTERSECTION

In this paper, the unsignalized T-shaped intersection is modeled by a cellular automata model. The main street and the minor street join at the intersection. As to the traffic flow is not controlled by traffic lights, conflict happens between the vehicles from minor street and that from main street. Two different crash avoiding rules are used to dispose the conflicts. In the first rule, the priorities are given to the driving-ahead vehicle and the vehicle on the main street. In the second rule, the vehicle that reaches the conflicting point earlier enters into the intersection. The flux on each lane depending on the inflow rates is studied in detail. The capacity of the system is also investigated. Our simulation results suggest that the two rules do not take the same effect on the capacity under different traffic conditions.