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.
To explore the mechanism of perceiving cyclist fatigue and seek the factors that influence the perception, this study designed and implemented a cycling experiment in different cycling environments. Based on the cycling data, including individual attributes, the intensity of cycling activity, and the physiological and psychological data of cyclists, collected from the cycling experiment, a fatigue perception model was developed using multivariable linear regression. The model described quantitatively the relations between cyclists’ perceiving fatigue state and their individual attributes, cycling activity intensity, and physiological and psychological loads. The linear significance and multicollinearity of the model were tested by using a statistics method. In addition, through implementation of another cycling experiment, the forecasting ability of the cyclist fatigue perception model in real cycling activities was verified. The analytical results show that perceiving cyclist fatigue is mainly influenced by the individual attributes of cyclists, the intensity of their cycling activities, and their physiological and psychological loads. Statistically, the influencing factor scores of the aforementioned attributes on fatigue perception were −0.291, 0.353, 0.253, and 0.265, respectively. This means that a positive correlation was found between fatigue perception and cycling activity intensity, the cyclists’ physiological and psychological loads, and their perception of fatigue, whereas the cyclists’ individual attributes had a negative correlation with fatigue perception. It should be noted that cycling activity intensity had the greatest effect on changes to the cyclists’ perception of fatigue. No significant difference was observed between the forecast and real values of the cyclist fatigue perception model. Based on these research results, this cycling system can be improved by reducing the physiological and psychological loads of cyclists during cycling, thereby reducing the expectation of the cyclists’ perception of fatigue during cycling and affecting their decision-making and cycling behaviors. This model also can be used in the field of bicycle evaluation and planning.
In this study, a 1/9 scaled tunnel was established, and experiments and numerical simulations were carried out using the LES method for three different fire source areas to investigate the distribution rules of temperature in a tunnel exposed to fire and provide a reference for tunnel fire protection design and rescue. The distribution characteristics of temperature along the tunnel ceiling and cross-section, as well as the heat release rate and the behaviors of fire overflow at the tunnel entrance were determined and analyzed. The experimental and numerical results indicate that small area tunnel fire is mainly controlled by the fuel owing to the relatively abundant air, and the temperature at the center of the combustion region is significantly higher than the temperature at the two sides and it continues to decrease along the longitudinal direction. Furthermore, the temperature distribution is stable and obvious stratification occurs. It was found that the simulation results of FDS and the experimental results are in good agreement. For large area tunnel fire, the combustion is mainly controlled by the ventilation owing to the relatively abundant air supply, and the fire intensity at the middle of the combustion region decreased owing to limited ventilation and lack of oxygen; thus, the temperature decreased, while fire on both sides is relatively intense. As combustion on both sides enters a weak phase, flammable vapors on both sides are reduced, and fuel in the middle of the combustion region burns intensely again owing to the abundant air supply. In this case, the simulation by FDS can also reflect the development of the fire. However, the simulation results indicate that the rate of increase in the temperature in the tunnel is higher and the combustion inhibition effect is more evident in the middle of the combustion region at the developing stage of the combustion. In addition, the growing trend of fire overflow of FDS is essentially consistent with the experimental results, and the simulation results can provide further details of fire overflow.
To guide drivers to use the automated driving system safely, this study investigated their performance during the takeover from automated driving to manual driving on a driving simulation platform. This study also investigated the factors influencing the switch mode between automated driving and manual driving in complex traffic environments. Driving behavior was analyzed in terms of driving speed, headway distance, vehicle lateral control, and vehicle steering behavior, and the associated data were collected from 36 subjects, who participated in two dangerous traffic situations. The results show that some subjects immediately switch the driving mode after the road situation prompt appears, while other participants undertake surveillance of the information pertaining to the road and vehicle after the prompt, and therefore, do not switch to manual driving until a traffic conflict is observed. It is found that the state (e.g., playing games or listening to music) of the subject before taking over the vehicle has an influence on the takeover time. The time to take over the vehicle in the case of the participants that were playing games is shorter than that of the participants listening to music. It is found that the switch mode has a significant influence on the lateral position of the vehicle as well, and the subjects that chose the first switch mode can keep driving at a relatively safe speed during the subsequent driving process, indicating that there is a correlation between “switching mode one” and “lower safe vehicle speed”, though the causal relationship between the two needs further investigation.
To promote the application of steel fiber reinforced recycled concrete (SFRAC) in road and bridge engineering, 11 different mixture proportions of SFRAC were designed and a total of 33 bond specimens of rebar and SFRAC were cast with the test parameters of the recycled coarse aggregate (RCA) replacement ratio (0%, 30%, 50%, and 100%) and steel fiber contents (0%, 0.5%, 1.0%, 1.5%, and 2.0% by volume). Pull-out tests were conducted for the bond specimens between the rebar with strain gauges inside and SFRAC. It was found that there were two or three bond stress peak values in the bonding segment between the rebar and SFRAC. The change in the bond stiffness at the different bonding positions is the main reason for the nonuniform distribution of the bond stress. The uniformity of the bond stiffness in the bonding segment increases by increasing the replacement ratio of the RCA, and 50% is the optimal replacement ratio of RCA. This is also improved by adding steel fibers into recycled aggregate concrete (RAC), but their effect decreases when its volume fraction is 2.0%. Furthermore, the relative slip at the loading end increases with the increasing replacement ratio of the RCA and decreases with the increasing volume fraction of the steel fibers. The uniformity of the bond stiffness in the bonding segment is improved with increasing replacement ratio of the RCA and volume fraction of the steel fibers. The peak values of the bond stress in the bonding segment next to the free end increase with increasing replacement ratio of the RCA and have little relation with volume fraction of the steel fibers. The shape of the bond stress and slip curve between the rebar and SFRAC does not change with the bonding positions. Finally, a constitutive model for the bond stress-slip relation of the rebar embedded in the SFRAC is proposed, which considers the influence of the replacement ratio of the RCA and volume fraction of the steel fibers.
To comprehensively quantify crowding and passenger transport efficiency of the equipment and facilities of a bus corridor and scientifically evaluate the sensitivity of objective technical index and subjective passenger perception to the level of the bus running condition, we proposed the conception of passenger congestion and passenger congestion index models. From the analysis of the correlation between subjective passenger travel time and passenger congestion and the characteristics of bus travel, the passenger congestion quantification model was formulated with a time multiplier for systematically evaluating the subjective perception of travel time and crowding. A visual analogy scoring SP survey was designed for data collection to estimate model parameters, incorporating four characteristic variables (passenger density in the carriage, passenger density on the platform, travel time, and waiting time) affecting the perception time. Applying the practical data of a Beijing Xisanhuan (West 3rd Ring Road) bus corridor, the all-day spatial-temporal distribution of section passenger congestion index and the dynamic evolutionary trend of the corridor passenger congestion index were studied. According to the results, based on the peak state threshold (the value of which is 0.193 9), the passenger congestion condition of the Xisanhuan bus corridor presents significantly directional distinction, and the peak-state is more remarkable and lasts longer in the downward direction. Furthermore, the average sensitivity coefficients of the four characteristic variables are 0.449 2, 0.165 2, 1.427 1, and 0.408 3, respectively, and travel time is the most significant factor of the passenger congestion index while passenger density on platform is the least, showing that the model is capable of distinguishing causes of congestion formation. This model has the advantage of comprehensively analyzing the spatial-temporal distribution and dynamic evolutionary trend of passenger congestion in a bus corridor and may hopefully be applied to research on improvement measures of bus running condition.
The purpose of this study is to improve the slope warning system using a monitoring method of fully grouted bolts and to promote the extensive application of this method. Experiments were conducted to determine the monitoring bolts’early warning thresholds and the safety classifications of slopes with a single sliding plane, based on the actual mechanical characteristics of bolts and the instability evolvement rule of slopes. First, for slopes with a single sliding plane using fully grouted bolt monitoring, when the strengthening and monitoring bolts were constructed and the grouting strength of bolts reached a stable value in a short time, the slope reached a steady state of stress adjustment and deformation development, which is identified as the initial monitoring state of the slope. Second, considering the negative evolutions of shear strength parameters of sliding planes, water pressure on the sliding plane, or earthquake, a preview numerical simulation analysis of plane strain was proposed to determine the sequences relative to the initial monitoring state of the slope, on the incremental accumulation of monitoring fully grouted bolts’axial force. Third, relative to the initial monitoring state of the slope, the increment in slope sliding force and the reduction in slope anti-sliding force induced by the negative evolutions were obtained using limit equilibrium stability analysis of slope. Hence, a fitting function with the incremental accumulation of monitoring fully grouted bolts’axial force was obatined, and a computational formula on the dynamic stability factor of the slope with the accumulation of monitoring fully grouted bolts’axial force was established. According to the regulations on slope safety classification and early warning in the GB50330-2013
Technical Code for Building Slope Engineering, etc., early warning classifications of the slope using a monitoring method of fully grouted bolts were blue (without alert), yellow (slight alert), orange (ordinary alert), and red (urgent alert). Finally, the slope example with a single sliding plane using the monitoring method of fully grouted bolts and its two independent calculation conditions of negative evolutions was designed to interpret the process of the proposed method for dynamic early warning analysis and safety classification of the slope. For similar slopes, it is first suggested to reasonably pre-judge the negative evolution rules of slope negative influences combining the existing relevant information, and then to to complete the analysis with the proposed method and obtain a reliable early warning result.
A load equivalent method is proposed to overcome the problem of the correlation characteristics between forces not being reproduced when each hinge force is compiled separately into the load spectrum and applied to the bench fatigue test. In other words, the load equivalent method is proposed to obtain the basic data that reflect the actual working situations of the stick and can be used to compile the programmed load spectrum for a bench fatigue test. Three-dimensional pin-shaft force sensors, pressure sensors, displacement sensors, and strain gauges are used to measure the time history of the stick’s hinge force connected to the bucket, cylinder force, rocker force, working posture, and stress of the critical fatigue measuring points on the stick. The loading scheme of the bench fatigue test in the local coordinate system of the stick is determined according to the change of each hinge force and the stick’s movement characteristics. On the basis of the stick cross section’s stress state, it is proposed that maintaining the consistency of stress at the maximum stress point of the stick’s maximum bending moment crosssection should be used as the load equivalent benchmark. Then, each hinge force on the stick would be equivalent to a unidirectional force. The calculated stress history caused by the equivalent load at each critical fatigue measuring point on the stick is compared with the measured stress history of the corresponding measuring point. The results reveal that the correlation degree of the two stress curves reach 97.21% at Point 1
# and 91.54% at Point 2
#, while it is slightly lower at Point 3
#, where it reaches 88.6%. In the mean time, at each critical fatigue measuring point, the calculated fatigue damage caused by the equivalent load is very close to the measured fatigue damage caused by the measured stress, which verifies the load equivalent method. Moreover, the load obtained by the equivalent method comprises the basic data for compiling the load spectrum for fatigue life prediction and the programmed load spectrum for the bench fatigue test.
