China Journal of Highway and Transport , the 1st in the field of road transport, is supervised by China Science and Technology Association and sponsored by Highway and Transportation Society of China. It is the most authoritative academic journal of the highway transportation industry. Launched in 1988, it has been walking in the forefront of road traffic technology development. Its scope covers the achievements in road construction and transportation, including road engineering, bridge and tunnel engineering, traffic engineering, road building and machinery engineering.
The journal is included by CA, JST, Pж(AJ), EI, CSCD.
The drive stability control system based on wavelet controller was studied for the front-wheel-independent-drive electric vehicle. With the equal torque allocation control strategy of driving wheel, the near slip ratio control strategy based on PID neural network (PIDNN) was proposed for improving the driving stability on the split road. A new controller based on DWT was studied using vector control. Through the co-simulation platform of CarSim/Simulink for the front-wheel-independent-drive electric vehicle, vehicle performance was analyzed and compared under different road conditions. Based on A&D5435, a rapid prototype test platform for front-wheel-independent-drive electric vehicles was built. The simulation and test results show that the drive stability control system based on wavelet controller not only improves the stability on split road, but also provides smoother and more rapid torque response. On the split road, the maximum deviation of the left and right driving wheel between the simulation result and test result are 3.43% and 3.56%, respectively, with the designed control strategy, and 3.86% and 3.25%, respectively, with the equal torque allocation control strategy. Therefore, the test results are consistent with the simulation results. Compared with the equal torque allocation control strategy, the peak side slip angle is reduced by 79.57% and the lateral deviation distance is reduced by 73.39% using the near slip ratio control strategy of driving wheel based on PIDNN.
To study the shear performance of local welded shear connector in the form of rebar mesh which is used in the composite deck system of steel and ultrathin ultra high performance concrete (UHPC), we performed 12 push-out tests considering the influences of weld length and interface adhesion. The load-slip curve and shear capacity of the welded shear connector were obtained. A dynamic explicit analysis method was employed to conduct the numerical analysis of the static push-out tests using ABAQUS software. The fatigue performance of the welded shear connectors with a weld length of 25 mm was preliminarily studied by conducting the fatigue push-out test. The results show that the shear capacity of the connector increases with the increase in the weld length. Additionally, the interface adhesion has no influence on the shear capacity of the specimen but will increase its shear stiffness in the elastic stage. Two failure modes exist according to the different weld length ratios of the longitudinal reinforcement, which are the shear failure of weld and the pulling out of the longitudinal reinforcement, respectively; both of them are brittle failures. The welded shear connector has a relatively high shear capacity and stiffness compared to the conventional shear stud connector. With regard to two different failure modes, the numerical results considering material and contact nonlinearity are in agreement with the test results. The welded shear connector does not demonstrate fatigue failure under shear stress amplitude of 80 MPa after experiencing five million cyclic loads, which satisfies the requirements of the fatigue design code. The relative interfacial slip of specimen grows slowly before failure occurs and rises rapidly during the failure phase.
Reduced-scale experiments were performed to investigate the optimal smoke control strategy in urban traffic link tunnels (UTLTs) by considering the challenges posed by the emergency ventilation and smoke control systems in these tunnels. The smoke and heat extraction efficiencies of a transverse ventilation system were examined via a tracer gas method. Moreover, the effects of two types of hybrid smoke control modes were investigated. The first method was the longitudinal ventilation combined with point extraction method, and the second was the longitudinal ventilation combined with natural smoke extraction. The results indicate that, if only the transverse ventilation system is adopted, both smoke and heat extraction efficiencies increase slowly with the extraction flow rate. Therefore, a high smoke extraction rate is required for the transverse ventilation system in UTLTs, and the requisite equipment may occupy large areas in the urban core districts. When the longitudinal ventilation combined with point extraction is adopted, it is difficult to prevent smoke from spreading into the upstream side of the fire using only the force of the axial flow fan; however, if the longitudinal ventilation flow is too strong, smoke would spread into the downstream branches as well. In the case of the combination of longitudinal ventilation and natural smoke extraction shaft, the natural ventilation shaft sizes should be set appropriately. The key parameters of the two hybrid smoke control modes mentioned herein are proposed as design references.
A large amount of steel slag is produced annually in China, but it is not utilized efficiently owing to the low cementation. For the potential cementation of steel slag, composition adjustment and activation of steel slag were performed to enrich the active Al
2O
3 and SiO
2 content by considering the slag’s composition and referring the clinker component. Based on the investigation of the previous Ca(OH)
2-based activation, Na
2SiO
4- and cement-based activation was attempted. At the optimal mass proportion of the steel slag composite (cement:metakaolin:slag equals 50:15:85), its strength after 90 days of curing and with a 0.28 water-binder ratio was 41.5 MPa. Clinker moduli were tentatively introduced to evaluate the performance of the composite, and the moduli of the composite activated by cement and lime were similar, suggesting a reference method for the standard preparation of the slag-based composite with different initial components. Microscopic techniques were adopted to clarify the strength generation mechanism, including the porosity, type, and pattern of the hydration products. The results show that the hydration products of cement-based activation are composed of C-H, C-(A)-S-H, C-A-H and C-S-H, and the main product is the reticular C-S-H, which fulfilled and connected the hydration matrix. The prolific hydration product as well as the smaller capillary pore size leads to the strength continuous generation. After 28 days of curing, the strength of the soft soil stabilized by slag composites activated by cement at the optimal ratio is 1.2 MPa with 20% incorporation. Furthermore, its strength reduces with the increase in water content. The strength of the stabilized soft soils is a function of the quasi-water-cement ratio, and a prediction method is proposed.
To solve the power interruption problem during the gear shifting process in a conventional automated mechanical transmission (AMT) system, a novel AMT (N-AMT) characterized by a planetary gear train installed on the conventional AMT was built. The basic structure was evaluated, and the working modes of the planetary gear train during parking, startup, and shifting conditions were analyzed. First, the initial speed ratio was designed based on the maximum ratio, minimum ratio, gear number, and adjacent speed ratio. Then, through combining the characteristics of “AMT shift” and “dual clutch transmission (DCT) shift”, the speed ratios of the AMT with planetary gear train were optimized by using genetic algorithm to minimize the fuel cost over New European Driving Cycle (NEDC) drive cycle under the condition of ensuring dynamic performance. Different gear number plans were designed by using this speed ratio design method. Based on the simulation of an 8-gear N-AMT and analysis of the dynamic and economic performance, the results indicate that the N-AMT with eight gears has the most optimal performance considering the overall structure, which is intended to be the final design. The simulation results indicate that the NEDC cycle fuel consumption of the 8-gear N-AMT is 6.38 L per 100 km, which is 8.86% less than the fuel consumption of a 5-gear AMT (6.95 L per 100 km). Finally, the startup and successive shifting bench tests of the 8-gear N-AMT were conducted, and the test results show that the dynamic interrupt in partial gears is eliminated and the dynamic performance is improved; the startup time of the 8-gear N-AMT is 1.55 s, which is 3.7% less than the 1.61 s of the 5-gear AMT. In addition, the shift time is maintained within 1.05 s, which ensures a better shift-feel.
The effects of drilling holes or slots in partial areas of traffic signboards on reducing wind loads were investigated. A test model was designed to employ one model to make different kinds of drilling holes or slots. Based on wind tunnel tests of the rigid model, pressure on signboards with 16 kinds of holes or slots were obtained. Characteristics of the mean wind pressure on signboards under different cases were then acquired, and the influence of single row of holes, single column of holes, multi-row holes, multi-column holes, and single and double slots on the characteristics of mean wind pressure, drag force coefficients, and torsion coefficients on the traffic signboard was analyzed. Finally, variations of the mean drag force coefficients with porosity and variations of the torsion coefficients with wind direction were investigated. The results showed that the drag force coefficient of a signboard varied little for wind directions between 0° and 45°; however it decreased almost linearly when the wind direction moved from 45° to 90°. For the 0° wind direction, the wind pressure coefficients on the windward of the signboard with holes or slots tended to be stable, whereas there was a small increase in the amplitude of the mean wind pressure around the hole or slot. When the porosity was less than 5%, the drag force coefficients were not sensitive to the porosity and the position of holes or slots, and the effects on reducing wind loads on signboards were attributed to the reduction of the net area of the signboard. When the porosity was greater than 5%, the reduction of drag force coefficients was relatively obvious. A fitted formula of the mean drag force coefficients with the porosity of the signboard with non-uniform holes was proposed. The maximum torsion coefficient appeared at the 45° wind direction. The mean torsion coefficients along the side vertical axis or the center vertical axis of the signboard with holes or slots were much smaller than those of the solid slab for oblique wind directions, and such reduction effects were more remarkable for the 45° wind direction or for the signboard with a large porosity.
It is an effective way for alleviating traffic congestion to use boundary flow control strategy to the extracted sub-network with the higher congestion degree in traffic network. Especially, existing compact macroscopic fundamental diagram (MFD) in objective sub-network is an essential prerequisite for boundary flow controlling. Based on the initialization areas partitioned by normal cut (Ncut) algorithm, the math model to find a sub-network with the optimal goodness of fit (GOF) in dynamic merging process is built in this paper. Then, after the analysis of the model, the greedy algorithm to solve this model is proposed. Finally, the method is applied to the traffic network of downtown of Idaho in Boise, the US. After analyzing the application and comparing the proposed method in this paper and Ji’s method, we find the method has a reasonable result. In addition, the network can be partitioned more evenly when the optimal solution is achieved. Hence, analyzing and comparing both the results of network partitioning and characteristics of MFD between timing control and adaptive control, we find that ① MFD characteristic of the sub-network with optimal GOF inherits the one of origin network, and the road resource utilization in the optimal sub-network is higher than that in the origin network; ② based on MFD characteristics of sub-networks with non-optimal GOF of MFD, the traffic situation of these sub-networks can be analyzed; ③ the optimization effect of using adaptive control in the network can be observed in MFD of both origin network and the sub-network with optimal GOF of MFD.
To improve the performance of engines fueled with a high proportion of biomass fuel blends, ethanol was added to medium-proportion biodiesel-diesel fuel blends by volume ratios of 5%, 10%, and 20%, respectively denoted as BD50 E5, BD50 E10, and BD50 E20. The combustion and emission performances of biodiesel-diesel-ethanol fuel blends were investigated on a supercharged common-rail diesel engine with six cylinders at a constant speed of 1 600 r·min
−1 and seven engine loads, and the engine performances of the fuel blends were compared to that of pure diesel fuel (BD0). The results show that the fuel injection system operates on multistage injection which combines pilot injection and main injection under light loads when the brake mean effective pressure (
pme) is equal to 0.322 MPa. The maximum cylinder pressure and the maximum heat release rates of the biodiesel-diesel-ethanol fuel blends are higher than that of BD0, because a large number of hydroxyl radicals are generated in the low-temperature reaction at the pilot injection stage. As engine loads grow, the fuel injection strategy becomes single-stage injection at
pme = 0.805 MPa. The maximum cylinder pressure and the maximum transient heat release rates of the biodiesel-diesel-ethanol blends are lower than BD0 owing to the lower caloric value of ethanol. Moreover, with the increasing proportion of ethanol, the ignition delay period of biodiesel-diesel-ethanol blends is obviously prolonged due to the lower cetane number and higher latent heat of vaporization of ethanol, and the combustion of the fuel blends are distinctly accelerated due to the stronger premixed combustion and the higher oxygen content of ethanol. Therefore, the addition of ethanol is helpful to concentrate the heat release and shorten the combustion duration. In terms of exhaust emissions, compared to those of BD0, NO
x emissions from biodiesel-diesel-ethanol fuel blends of BD50E5, BD50E10, and BD50E20 increased by 10.46%, 12.59%, and 17.52%, respectively; whereas, soot emissions decreased by 37.91%, 45.85%, and 49.25%; CO emissions declined by 20.24%, 36.43%, and 46.43%, and HC emissions fell by 12.53%, 4.40%, and 0.76%, respectively.
