20 March 2020, Volume 33 Issue 3
    

  • Select all
    |
    Review
  • Systematic Review on Anti-speeding Countermeasure Research
    JIANG Xin-guo, LIU Hai-yue, ZHOU Yue, FU Chuan-yun
    China Journal of Highway and Transport. 2020, 33(3): 1-31. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To conceive effective anti-speeding countermeasures and determine practical effectiveness, adaptation conditions, advantages and disadvantages of existing anti-speeding countermeasures, and the effectiveness of combined countermeasures,relevant literature were systematically reviewed. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines, speeding and its corresponding countermeasures were regarded as keywords. In this study, 11 electronic databases were employed to search for relevant literature regarding the automated speed enforcement system, anti-speeding advertising measure, speeding warning sign, and intelligent speed adaptation system. Literature quality assessment indexes were established to evaluate the searched literature. In total, 101 studies were included in the review. Findings of the studies were synthesized in a narrative analysis. The research results indicate that the automated speed enforcement system, anti-speeding advertising measure, speeding warning sign, and intelligent speed adaptation system have varying anti-speeding effectiveness, which are affected by some road, traffic, and environmental conditions and human factors. Specifically, with regard to the automated speed enforcement system, the point-to-point speed enforcement system outperforms others, whereas the mobile speed camera system follows others; with respect to the anti-speeding advertising measure, outdoor advertisement outperforms other advertising measures, whereas print advertisement has little effect; as for the speeding warning sign, public posting of speeding information has a significant anti-speeding effectiveness; moreover, the warning dynamic speed display sign is superior to the standard one; as for the intelligent speed adaptation system, the compulsory intelligent speed adaptation system performs better than the others; however, the voluntary intelligent speed adaptation system demonstrates the worst performance. Additionally, most combined anti-speeding countermeasures perform better than a single countermeasure. In summary, the automated speed enforcement system outperforms three other anti-speeding measures, followed by the intelligent speed adaptation system, speeding warning sign, and anti-speeding advertising measure. Furthermore, combined countermeasures evidently improve intervention effectiveness. The abovementioned findings provide evidences for the selection and conceivement of anti-speeding countermeasures. Aimed at overcoming the limitations and determining the unclear influence factors of the existing anti-speeding measures, future studies need to optimize experimental and observational schemes to further examine the effectiveness and corresponding influence factors of the anti-speeding measures. Furthermore, additional studies need to be conducted to propose novel anti-speeding countermeasures based on big data (such as vehicle trajectory and video data).
    • Road Engineering
  • Vibration Characteristics of Cross-tensioned Concrete Pavement
    CHEN Hui, LING Jian-ming, ZHAO Hong-duo, ZENG Meng-yuan, WU Di-fei
    China Journal of Highway and Transport. 2020, 33(3): 32-41. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This paper aims to explore the effect of prestress force on the vibration characteristics of cross-tensioned concrete pavement (CTCP) using numerical simulation and field testing. A full-scale test was conducted and different prestress forces were simulated by grading tension. Accelerometers were used to collect the vibration data and Fast Fourier Transform analysis was introduced to obtain the vibration features. Then, finite element (FE) models of CTCP were built using ABAQUS to collect the acceleration and extract spectral features of the CTCP when subjected to different prestress forces. A parametric study was developed to evaluate the influence of parameters (i.e. modules, densities, and friction coefficients) on dynamic response. Test results show that the change in first-mode frequency is not obvious with increasing prestress force, indicating that the traditional vibration features cannot guarantee sufficient sensitivity to the prestress force of CTCP. However, the frequency band of 50-150 Hz under different prestress forces is much different compared with the low-frequency band. As the prestress force increases, the spectral components of the high-frequency band increase and the frequency curve gradually shifts to the right. A good correlation between the weighted frequency and the prestress force is also observed. Meanwhile, it was also found the spectral distribution is more sensitive to prestress force compared to other parameters, indicating that the prestress force can significantly influence the frequency band of 50-150 Hz. These works suggest that the weighted frequency can be employed to study the changes in the spectral distribution.The analysis of vibration characteristics can be used to identify the change in prestress force.
  • Identification of Cavities Underneath Concrete Pavement Based on Pavement Vibration
    ZENG Meng-yuan, ZHAO Hong-duo, WU Di-fei, CHEN Hui, LING Jian-ming
    China Journal of Highway and Transport. 2020, 33(3): 42-52. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Cavities beneath concrete pavement slabs, usually resulting from erosion or foundation settlement, increase the flexural-tensile stress in the slabs, which may cause distresses, such as joint faults and fracture. To avoid such distresses, this study proposes a vibration-based method for the identification of cavities underneath concrete pavements. Through finite element analysis, it was found that the cavities significantly affected the local vibration characteristics in terms of the frequency spectrum; however, they had negligible effects at other positions. Additionally, the location and extent of the cavities affected the local frequency spectrum. On this basis, a distributed optical vibration sensing-system (DOVS) was developed and utilized to measure the vibration characteristics of the concrete pavement. Furthermore, a laboratory test was conducted to study the influence of the extent of cavities, and the frequency spectrum was obtained using time-frequency analysis. The correlation between the frequency spectrum and the extent of cavities was studied, and it was observed that the spectrum of 20-150 Hz was sensitive to the extent of cavities, and hence, an index expressed as "weighted frequency" was used to identify the cavities. During the field tests, the DOVS was established in three concrete pavement slabs at Longhua Airport, Shanghai. This vibration-based cavity identification method was compared with other conventional deflection-based methods, and a good coherence was observed between the identification results of these two methods, indicating that the vibration-based method is reliable for cavity identification.
  • Optimum Selection Analysis of Waterproof Bonding Materials for Steel Bridge Deck Based Using Entropy Weight-TOPSIS
    AI Chang-fa, HUANG Heng-wei, RAHMAN A, AN Shao-ke, REN Dong-ya
    China Journal of Highway and Transport. 2020, 33(3): 53-63. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This study is aimed at identifying the optimal waterproof bonding materials for building the asphalt pavement structure of a bridge deck. To this end, firstly, concrete composite specimens of steel plate and asphalt were fabricated with different waterproof bonding characteristics. Secondly, the direct tensile strength (DTS), direct shear strength (DSS), and skew shear strength (SSS) of the composite specimens were measured at low (0℃), normal (25℃), and high (70℃) temperatures. Additionally, the fatigue lives (FLs) of the composite specimens were measured at the normal temperature by using a universal testing machine (UTM). An evaluation index system was developed for the waterproof bonding materials used to build a steel deck on a bridge. The index comprised of DTS, DSS, 45° SSS, FL, and material cost (MC). The weight of the evaluation index was balanced using the information entropy theory. Subsequently, the comprehensive performances of the different composite specimens were compared using the Technique for Order of Preference by Similarity (TOPSIS). The optimal waterproof bonding materials to build the steel deck on a bridge were identified using a combination of the entropy weight method and TOPSIS, i.e., the entropy weight-TOPSIS method. Finally, the obtained results were validated using image binarization. The results of the image binarization analysis are consistent with those of the entropy weight-TOPSIS method. This confirms that the entropy weight-TOPSIS method is the optimal method for identifying waterproof bonding materials to build steel decks on bridges. Furthermore, the method eliminates the influence of subjective factors, and is objective as well as effective in the selection of the optimal waterproof bonding materials for manufacturing steel decks.
  • Influence of Temperature Change on Deformation of Coarse-grained Sulfate Saline Soil Subgrade
    YANG Xiao-hua, LIU Wei, ZHANG Sha-sha, XIAO Fei, CHEN Wei-zhi
    China Journal of Highway and Transport. 2020, 33(3): 64-72. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Coarse-grained sulfate soil roadbeds are prone to excessive deformation problems, such as salt expansion and subsidence owing to changes in ambient temperature, and the impact on normal use of the roadbed cannot be ignored. In view of these problems, a test section was selected at the construction site of the Tehran-Qom-Isfahan high-speed railway project in Iran, and long-term monitoring of the roadbed temperature and moisture content was carried out. The variation of temperature and moisture content of the roadbed with time was analyzed. Based on this, a self-designed temperature change test device and field roadbed filling were used to conduct indoor temperature change cycle model tests to study the deformation characteristics of coarse-grained sulfate saline soil. The results show that during the monitoring period, the sensitive depth of the subgrade temperature in the field test is 0.22 m, and the moisture content of the subgrade within the depth of 1.0 m varies greatly. During the nine-cycle test, the temperature and moisture content of the sample depth in the range of 20 cm become more significant over time. However, with a change of the test temperature, there is a certain hysteresis in the change of sample temperature. The soil sample with 1.5% salt content shows salt expansion deformation and frost heave deformation in the first and second temperature change cycle tests, with a maximum deformation of 0.128 mm. The soil sample with 3% salt content exhibits such deformation in the first six cycles of the test, with a maximum deformation of 0.232 mm. Due to the influence of multiple factors such as temperature, ice-salt transformation, salt content, soil particle composition, and test cycle, specimens with different salt content eventually experience subsidence deformation after nine test cycles. The subsidence deformation of the sample with 1.5% salt content is 0.585 mm, which is 5.42 times the final subsidence deformation of the soil with 3% salt content. The research results can provide certain technical references for related projects.
    • Bridge Engineering
  • Regional Variation and Zoning of Temperature Gradient Pattern of Concrete Box Girder
    LIU Jiang, LIU Yong-jian, BAI Yong-xin, LIU Guang-long
    China Journal of Highway and Transport. 2020, 33(3): 73-84. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To investigate regional variation and zoning of temperature differences and temperature gradient in concrete box girders, long-term temperature field measurements of a concrete box girder bridge were conducted. The vertical temperature gradient curve of the box girder was given by the measured data. Then, a generalized extreme value distribution was applied to obtain representative values of the temperature differences. Finite element models were established to calculate the temperature differences of concrete box girders in 34 major cities in China. Geologic factors and meteorological factors were used as parameters to obtain the empirical formula of the representative values of temperature difference. Based on this, the representative temperature difference values for 361 Chinese cities were calculated and zoned preliminarily. The results show thatthe vertical temperature gradient curve of the box girder based on the measured data conforms to the form recommended by the New Zealand Code, with "5th parabola at top" and "linear distribution at bottom." The temperature difference at top (T1)and at bottom (T2) of the concrete box girder can be subjected to the Weibull distribution with parameters of W (6.86, 4.49, -0.42) and W (-0.32, 1.46, -0.40), respectively. The representative values of T1 and T2 for the concrete box girder in Dongguan, Guangdong Province are 17.3℃ and 3.1℃ for a 50-year return period, respectively. In this paper, the empirical formula of the representative values T1,ref and T2,ref is established with the latitude l, the altitude H, and the daily air temperature difference TV, and can be verified by the results of existing research. The formula can fully reflect the regional variation of the temperature difference in concrete box girders in China. Based on the regional variation of the representative values of temperature difference, China can be divided initially into four zones by their temperature difference values. The values of T1,ref in the four zones are 18℃, 20℃, 23℃, and 29℃, respectively. In addition, the values of T2, ref in 4 zones are 4℃, 5℃, 6℃ and 7℃, respectively. The empirical formula and the zoning map proposed in this paper are only applicable to concrete box girder with 100 mm asphalt pavement. The method and conclusion of the research can provide reference for the improvement of China's design code regarding the temperature action of concrete box girder bridges.
  • Time-dependent Reliability Assessment of Concrete Bridges Considering Non-stationary Vehicle Load and Resistance Deterioration Processes
    YUAN Yang-guang, HAN Wan-shui, XIE Qing, LI Guang-ling, XU Xin
    China Journal of Highway and Transport. 2020, 33(3): 85-96. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This study attempts to realize a time-dependent reliability assessment of components of existing concrete bridges by considering the processes related to non-stationary vehicle load and non-stationary resistance simultaneously. First, a dynamic generalized extreme value distribution within a time domain and a Monte Carlo simulation were combined to conduct extreme value modeling of the non-stationary vehicle load process. A Gamma process based non-stationary resistance deterioration modeling and corresponding updating procedure were then introduced. Second, the principles of marginal life-saving cost, individual risk, and social risk were considered to determine the target reliability index in the operational stage as these can provide basic safety criteria for a time-dependent reliability assessment. Finally, a risk-function-based analytical method was established to realize the time-dependent reliability analysis by including non-stationary factors. For this method, the Gaussian numerical integration and Taylor series expansion were introduced to overcome the solving problems. A case study was conducted to illustrate the application of the proposed analytical procedure. The results indicate that the extreme type I distribution can be used to describe the annual maximum distribution when the sectional distribution of load parameters exhibits a multimodal distribution. Traffic growth can lead to an increase in the number of location parameters and a decrease in the number of scale parameters of the annual maximum distribution. It is suggested that the annual target reliability index of existing concrete bridge components can be 3.98 when considering the three types of principles and that the effects of the reference period must not be neglected. When the time-dependent reliability assessment is conducted, the following information can be derived:the variation in the reliability index over a long period, the critical moment that the safety level of a component reaches the safety criterion, and the variation in the reliability redundancy. The obtained information can provide some direct references to plan lifetime maintenance strategies for existing concrete bridges.
  • Seismic Damage Control Design for Double-deck Bridge Bents Based on Rocking Self-centering System
    SUN Zhi-guo, ZHAO Tai-yi, WANG Dong-sheng, HAN Qiang, GUAN Lu
    China Journal of Highway and Transport. 2020, 33(3): 97-106. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To achieve seismic damage control design, a new reinforced concrete (RC)double deck bridge bent was proposed. In this bent,the upper precast piers were designed as rocking self-centering (RSC) structures. The lower precast piers were designed with a socket connection but without rocking behavior. A design method was proposed for the unbonded prestressing tendon and energy dissipation steel angle used in this new double-deck bridge bent. Seismic analysis models for normal RC and new RSC bridge bents were developed based on design details of the irregular double-deck bridge bent of the Luotanghe Bridge in Gansu Province. The accuracy of the modeling technique was verified against shake table test results for a RSC bridge bent conducted by the Pacific Earthquake Engineering Research Center. Then,dynamic time history analysis was conducted for both the RC and RSC bridge bent models under a series of 40 near-fault ground motions. The seismic behaviors of the normal RC and new RSC double-deck bridge bents were obtained and compared.The results show that the maximum story drift ratio of the upper piers in the RSC bent is slightly larger than that in the upper piers of the normal RC bent, whereas the maximum story drift ratio of the lower piers in the RSC bent is only 47% of that in the lower piers of the normal RC bent. The residual story drift ratios of the upper and lower piers in the RSC bent are only 2% of those in the upper and lower piers of the normal RC bent. The seismic shear force demand of the lower pier in the RSC bent is evidently reduced as compared with that in the lower pier of the normal RC bent. The stress of the unbonded prestressing tendon in the RSC bent remains in the elastic region. The steel angles will yield and dissipate seismic energy while no rupture damage is observed. Therefore, the proposed design method can effectively avoid seismic damage to double-deck bridge bents.
  • Full-scale Experiment on Stiffness Degradation and Identification of Prestressed Concrete Box Girders
    ZHOU Yong-jun, ZHAO Yu, ZHOU Ying, YAO Heng-ying
    China Journal of Highway and Transport. 2020, 33(3): 107-118. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study stiffness degradation under damaged conditions for prestressed concrete (PC) girders, a full-scale model test was conducted on three 30 m PC box girders. First, static and dynamic stiffness identification models of damaged beams were developed. The equivalent static stiffness was calculated based on beam deflections in the mid-section, and the equivalent dynamic stiffness was calculated based on its natural frequencies. Second, full-scale girders were loaded incrementally, and static and dynamic tests were conducted alternatively. The development of cracks, deflections, and frequencies of the experimental girders under different loads were then studied, and the effects of damage conditions on these parameters were analyzed. Third, the reduction coefficients of dynamic stiffness were derived using the finite element model updating method, and the relationship between static and dynamic stiffness with the damage conditions was analyzed. The difference between the static and dynamic stiffness was then explored. Finally, the regression formula of the reduction coefficients of the static and dynamic stiffness with crack feature parameters was established and compared with previous studies. The results show that the initial damage condition of the girder has an effect on the statistical distribution of the crack features. It also illustrates that the degradation of equivalent static and dynamic stiffness of the girder is not consistent, where the final reduction coefficients of static and dynamic stiffness are 0.30 and 0.80, respectively. The reduction coefficient of static stiffness between the full-scale and scale-down model tests is different. The study presents a simple method for the reduction coefficients of static and dynamic stiffness to assess damaged PC box girders in practical engineering.
    • Tunnel Engineering
  • An Analytical Solution for Stress and Displacement of Surrounding Rock for a Shallow Tunnel with a Cavity in Strata Considering Gravity Condition
    YANG Gong-biao, ZHANG Cheng-ping, CAI Yi, MIN Bo
    China Journal of Highway and Transport. 2020, 33(3): 119-131. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the stress and displacement of the surrounding rock for a shallow circular tunnel with a cavity in the strata, an analytical model in which the interaction between the tunnel and the cavity as well as the influence of gravity can be considered was proposed. The complex function method and Schwarz alternating method were applied to solve the model theoretically. Then, the analytical solution in this study was compared with the finite element numerical solution, and the results showed that they were in good agreement. Based on the analytical model, the effects of the stress release coefficient and position and size of the cavity on the stress and displacement were analyzed. The results showed that the influences of the cavity increase gradually with increase of stress release coefficient and cavity size but decrease with the distance between cavity and tunnel. The influence is the most significant when the cavity is located in the tunnel vault, followed by the inclined top. The hoop stress is decreased in the range of 0-5° but increased in the range of 5°-45° on both sides of the line between the centers of the cavity and the tunnel. The maximum differential subsidence is located directly above the cavity. The research has important theoretical significances and application values for the prediction of deformations and stresses caused by a shallow tunnel with a cavity in the stratum.
  • Influence of Shield Yawing Angle Variation on Shield-soil Interaction
    SHEN Xiang, YUAN Da-jun
    China Journal of Highway and Transport. 2020, 33(3): 132-143. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To determine the shield-soil interaction mechanism during the shield tunneling process, and to guide the control and adjustment of the shield attitude, considering the influence of the yawing angle variation on the shield-soil interaction, the theoretical calculation method of the earth pressure around the shield shell and the prediction model of the yawing angle were studied. First, based on the foundation reaction curve, an equivalent spring approximation model was used to establish the shield-soil interaction model. The displacement of the surrounding soil layer during the yawing angle variation was calculated based on the geometric analysis. The theoretical calculation method of the surrounding earth pressure acting on the shield shell was established. Then, the improved loose earth pressure calculation method was conducted, and the calculation method of the initial earth pressure of the shield was established. The initial boundary problem of the yawing angle calculation was solved, and the calculation method of the yawing angle of was obtained by combining the calculation method of the action load of the soil with that of the shield. Then, based on the established theoretical calculation model, the effects of shield mass, stratum type, and stratum excavation loss rate on the shield-soil interaction were analyzed and discussed. Finally, combined with the Jinan Metro R2 shield tunnel project, the yawing angle of the shield and other driving parameters were monitored in real time and compared with the theoretical value of the shield yawing angle. The results demonstrate that the influence of shield quality and formation excavation loss rate on the shield attitude in the horizontal plane is small; the different types of strata and the earth pressure coefficient of the stratum have a greater influence on the shield-soil interaction; the trend change of the theoretical value of the shield yawing angle is basically consistent with that of its measured value. However, because the bending moment applied by the shield itself cannot fully affect the shield machine, the theoretical value is generally greater than the measured value.
  • Pore Size Analysis and Its Influence on Slurry Infiltration in Sandy Layers
    MIN Fan-lu, LYU Huan-jie, SONG Bang-hong, WANG Yi-sheng, SONG Hang-biao, LIU Lai-cang
    China Journal of Highway and Transport. 2020, 33(3): 144-151. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.012
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To determine the pore size distribution characteristics of sand formation and its influence on slurry penetration in the formation, the sand formation pore sizes of five groups of uniformly sized particles were measured using the mercury injection test. The calculation method for the formation pore size was improved based on the straight pipe method with reference to the calculation method for the sand gravel filter pore size by Sherad et al. Simultaneously, nine groups of slurries with different properties were prepared to conduct the slurry permeability test on the sand formations with different pore sizes. According to the results of the permeability test, the relationship between formation pore size and slurry particle size was discussed. Taking as an example the forming filter cake with an infiltrated zone in the slurry permeability test, the influence of sand formation pore size on the permeability of the slurry in the formation is analyzed using the change in the permeability flow of the slurry in the formation and by calculating the change of the formation permeability coefficient. The results show that the average pore size calculated based on the straight pipe method is consistent with the pore size measured using the mercury injection method; that is, the pore size of the most frequent pore in the formation. The calculation method considering the adjustment of seepage velocity and seepage diameter as per Darcy's law, is suitable for a sand formation with a uniform particle and pore sizes. When slurry penetrates a high-permeability formation, the larger the pore size of the formation, the larger the particle size of the slurry required to form a filter cake or a filter cake with an infiltrated zone. The pore size of the formation directly determines the particle size of the slurry particles passing through the pores. The slurry particles infiltrating the formation pores form a stable silting, which changes the physical structure, reduces the permeability of the formation, and hinders the penetration of the slurry. The corresponding relationship between formation pore size and slurry particle size is the key factor affecting slurry permeability.
  • Experiment on Local Resistant of Grid in Tunnel Ventilation Model Test
    WANG Ya-qiong, LI Lin-feng, LAI Kai, YANG Shuai, XIN Yun-xiao, XIE Yong-li
    China Journal of Highway and Transport. 2020, 33(3): 152-159. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.013
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Due to the limitation of the test site and test conditions, it is usually to build a 1:1 scale model or a reduced model at the same scale. Therefore, on the premise that the prototype is similar to the model resistance, according to the equivalent design theory, the installation of resistance grid in the tunnel ventilation model can effectively shorten the length of the tunnel model. In order to solve the problem of selecting and setting the resistance grid in the ventilation model, the physical model is established for experimental test, and the experimental results are analyzed and compared. Among them, the influence of different resistance grid series spacing, series number and grid type on the local resistance of ventilation test is studied. The results show that adding resistance rack in the model, the automatic zone still exists, its critical speed of the wind is almost equal to the wind speed of the model; when the grid spacing is greater than three times of the model section, the interaction between the grid can be neglected, so the gap of the resistance rack should be longer than triple equivalent diameter of the section of the model; every rack of the part of the resistance loss factor is getting lower with the rising of the rack number, the lowing speed is getting smaller with the rising of the rack number. When selecting resistance grid, when the local resistance coefficient of grid is required to be large, porous plate can be selected as resistance grid, and square porous plate is preferred; when the local resistance coefficient of grid is required to be small, wire mesh can be selected. The research results provided guidance for the selection and setting of resistance grid in model test, and introduced the specific application of resistance grid in tunnel ventilation model test.
  • Research on Evaluation Method of Lining Safety Based on Ultimate Bearing Capacity Curve of Lining Section
    WU Xu, SUN Ming-she, XIA Yong, HAN He-geng, SUN Zuo-qiang
    China Journal of Highway and Transport. 2020, 33(3): 160-169. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.014
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Composite lining, which consists of initial support, a waterproof layer, and lining, is the main structural form of mountain tunnels in China. In these tunnels, lining is key in ensuring long-term operation safety. At present, the safety evaluations of lining structures are generally carried out according to the relevant tunnel design specifications.For the safety evaluation method of lining structure given in the current code, the checking formulas of plain concrete lining and reinforced concrete lining are provided,respectively.It is not possible to compare the safety of lining structures using the safety factors for the internal force states of lining sections. In this study, the current safety evaluation method of lining structure was firstly simplified, and the concept of the safety envelope of a lining section was proposed. Then the safety of a lining section could be judged according to whether the internal forces of the lining section were located inside the safety envelope. Furthermore, on the basis of discussing the relationship between the section safety envelope and ultimate bearing capacity curve, an evaluation method of lining safety based on the section ultimate bearing capacity curve was proposed. The results show that the safety envelope of the lining section can be used to judge the safety of the section simply and intuitively. The state of section internal forces (M, N) is located on the geometric similarity curve of the ultimate bearing capacity curve with respect to coordinate origin.By the geometric relationship of the relevant line segments, section safety factors can be calculated. The section ultimate bearing capacity curve considering the material nonlinearity can avoid some limitations in comparison the safety for both plain and reinforced concrete lining in the code. These research results are useful for section safety evaluations and lining design theory.
    • Traffic Engineering
  • End-to-end Autonomous Driving-behavior Decision Model Based on MM-STConv
    ZHAO Xiang-mo, LIAN Xin-yu, LIU Zhan-wen, SHEN Chao, DONG Ming
    China Journal of Highway and Transport. 2020, 33(3): 170-183. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.015
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Prediction inaccuracy is caused by the single-input data type of the existing end-to-end autonomous driving model. To solve this problem, RGB images, depth images, and vehicle historical continuous motion state sequences were selected as multi-modal inputs, and semantic information was utilized simultaneously to construct a multimodal multitask of spatial-temporal convolution (MM-STConv) end-to-end behavior decision model based on spatial-temporal convolution. This model obtained the multi-task prediction parameters of speed and steering. First, the spatial features of the scene were extracted through convolutional neural networks with different complexities, and the spatial feature extraction sub-network was constructed to accurately analyze the scene target spatial features and semantic information.Second, an LSTM encoder-decoder architecture was used to capture the temporal context features of the scene, and the temporal feature extraction sub-network was constructed to understand and memorize the scene temporal series information. Finally, a multi-task prediction sub-network was constructed with the hard-parameter sharing method, which outputs predicted values of speed and steering angle to predict vehicle behavior. In this study, virtual scene data were collected based on the AirSim autonomous driving simulation platform, and images of 98,200 virtual frames and the corresponding vehicle speed and steering angle labels were used as training sets. After 10,000 training cycles and 6 h of training time, a real driving-scene data set (BDD100K) was employed for testing and validation of the proposed model. The experimental results show that the training error of the MM-STConv model is 0.130 5, the prediction accuracy reaches 83.6%,and the prediction effect is better in a variety of real driving scenarios. Compared with other state-of-the-art existing models, the proposed model integrates scene spatial information and temporal series information, and has obvious advantages in predicting vehicle speed and steering angle, which can improve the prediction accuracy, stability, and generalization ability of the model.
  • Network Green-wave Band Model Permitting Relaxation of Constraints
    WANG Hao, YAO Dong-cheng
    China Journal of Highway and Transport. 2020, 33(3): 184-194. https://doi.org/10.19721/j.cnki.1001-7372.2020.03.016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of the regional traffic signal control domain in which the feasible region becomes narrow or even empty in a network green-wave band model, a novel model permitting the relaxation of constraints is proposed. The model was constructed as a mixed integer linear program in which the weighted sum of the green waves' bandwidths of all road segments was taken as the objective function. A constraint relaxation method was used to transform the constraints related to arterials and the network outer loops into relaxation-enabled inequality constraints. The model introduced a 0-1 binary variable for each road segment, indicating whether the green wave of the segment is interrupted. In this way, the model relaxed the outer loop constraints, thereby expanding the feasible region and finding the optimal solution. The optimized results of different models under different signal timing schemes were compared in an example network. When the intersections of the network adopted the homogeneous signal-timing scheme, it was easy to find the optimal solution without interrupting the green wave of any road segment.In this case, the solution of the proposed model was equivalent to the solution of the traditional network green wave model.When the intersections of the network adopted the heterogeneous signal timing schemes, the regular network green wave model failed to find solutions and the network green wave model built by Gartner only obtained non-optimally feasible solutions. In contrast, the proposed model could obtain a global optimal solution. Under this circumstance, the green wave of only one road segment was interrupted, while the other road segments achieved effective green wavebands and the arbitrary intersecting green waves could be reasonably coordinated. The results indicate that the proposed model is better than the regular network green wave model and the network green-wave model built by Gartner; the proposed model is more suitable for complex urban traffic network signal optimization.
News More>>
Download More>>
Links More>>
New Media
  • Wechat Account
  • WeChat video Account
Visited
    Total Visits:    Today:    Online:
Copyright © China Journal of Highway and Transport, All Rights Reserved.
Tel: 029-82334387　
E-mail：zgglxb@163.com
Powered by Beijing Magtech Co. Ltd,.