交通运输工程学报

Research progress of bitumen microstructures and components

TAN Yi-qiu, LI Guan-nan, DAN Li-yan, LYU Hui-jie, MENG An-xin

Abstract: To further promote the development of bitumen microstructures and components, the research progresses of bitumen chemical component, microstructure theory, simulation, and experimental methods were summarized. The physical and chemical properties of four components of bitumen, and the influence of wax and heteroatoms on bitumen microstructure were investigated. The bitumen microstructure was studied by combining bitument colloid theory and modified Yen model. The molecular dynamics and phase-field method commonly used in bitumen microstructure research were analyzed. The research progress of gel permeation chromatography, infrared spectroscopy, small angel scattering technology, microscopy technique in the study of bitumen microstructure was summarized. Research results show that bitumen should be regarded as a chemical continuum system. The molar mass, hydrogen to carbon ratio, and the polarity of molecules in bitumen gradually change in the order of saturate, aromatic, resin, and asphaltene. Waxes with a main carbon chain greater than C40 can be regarded as asphaltene components. The oxygen, nitrogen, and sulfur heteroatoms of bitumen exist in the form of characteristic functional groups in the polar components such as asphaltenes, resins, and aromatics, which are key parameters of bitumen molecular structure and are closely related to the adhesion properties of bitumen-aggregates. The colloidal state of bitumen is the microstructural basis of the viscoelastic behavior of asphalt. The modified Yen model can further explain the bitumen colloid theory. When asphaltene concentration is lower than the critical concentration of nano-aggregates, bitumen microstructure turns to the sol. When asphaltene concentration is gradually higher than the critical concentration of nano-aggregates, clusters and flocculation appear in bitumen, and bitumen microstructure changes from sol to gel. The molecular dynamics and phase-field method are widely used to simulate bitumen microstructure, but both two simulation methods simplify bitumen microstructure, there is still existing a huge challenge in the multi-scale simulation method based on microstructure simulation. One of the important development directions in bitumen material science is to combine bitumen chemical composition, bitumen colloid theory, and rheology characteristics to establish a complete mechanical constitutive relationship.More>

2020, 20(6): 1-17. doi: 10.19818/j.cnki.1671-1637.2020.06.001

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Review on ship speed optimization

YUAN Yu-peng, WANG Kang-yu, YIN Qi-zhi, YAN Xin-ping

Abstract: The status of ship speed optimization research in domestic and overseas, including ship speed optimization models, fuel consumption prediction methods, solutions of ship speed optimization models, and ship energy efficiency management systems, were summarized and analyzed. The existing problems in speed optimization research were discussed, and suggestions were made to solve these problems. Analysis result shows that, under the condition in which the shipping market continues to be depressed, economic navigation will be used more widely, and research on speed optimization will remain of great significance.In terms of speed optimization models, most speed optimization models are established with carbon emission policy, influence of uncertain factors, emission control area(ECA) policy and fleet scheduling as a single optimization objective. The main optimization objectives of speed optimization models are to minimize the cost and maximize the profit. Speed should be combined with route, trim and fleet deployment optimization, and a model of speed optimization should be established considering various uncertain factors and optimization objectives in the future.In terms of fuel consumption prediction model, prediction models are mainly divided into white box, black box, and gray box models. The white box model is better in terms of model interpretability, the black box model offers better prediction performance, and the gray box model compensates for the disadvantages of the white box model and the black box model and will become the focus of future research.Data learning should be based on accurate ship data and advanced artificial intelligence algorithms to improve the prediction accuracy of fuel consumption prediction model.In terms of optimization algorithm, due to the complexity of speed optimization model, heuristic algorithm is mostly used for optimization solution. This algorithm can reduce the optimization solution time and improve the solution quality. More accurate and efficient solution algorithms need to be explored in the future.In terms of optimization strategy, the use of big data analysis can identify the influence of weather on navigation, and the use of dynamic optimization strategies can compensate for disturbances caused by environmental factors, enabling further improvement in the energy efficiency of ships.In terms of ship energy efficiency management system, the ship energy efficiency management system mainly includes navigation data acquisition, data transmission, data storage, data analysis and intelligent decision making, it has not been applied on a large scale on ships as its high cost.More>

2020, 20(6): 18-34. doi: 10.19818/j.cnki.1671-1637.2020.06.002

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Review on research on concrete beam reinforced with HB-FRP

ZHANG Feng, GAO Xiao-hua, GAO Lei, WU Yu-fei, ZHU Shi-chao

Abstract: To summarize the research results of hybrid bonding fibre reinforced plastic(HB-FRP) reinforcement method and promote its broader application in the field of concrete beam repair and reinforcement, the research status of HB-FRP reinforcement method was investigated. The debonding problem of external bonding FRP under external loads and environmental erosion was revealed. The working mechanism of HB-FRP reinforcement in inhibiting debonding after FRP reinforcement was explained. The structural characteristics of HB-FRP reinforcement system and its influence on the interface bonding performance were analyzed. Existing bonding-slip and debonding load models were summarized. The flexural and shear performance of reinforced beam was studied. The shortcomings of existing studies were analyzed, and future research directions and ideas were prospected. Analysis result shows that both external loads and environmental erosion may induce the debonding of FRP. HB-FRP reinforcement combines the chemical bonding, friction and dowel effect to inhibit the FRP debonding effectively. The main difference among several current HB-FRP bond-slip relationships is whether a stable FRP slip occurs when the interfacial bonding strength is reached. The limit debonding load of the bonding interface depends on its bond-slip relationship. HB-FRP reinforcement can be used for the flexural resistance of normal section and the shear resistance of oblique section, and the bearing capacity and reinforcement efficiency of reinforced beam improve significantly. Increasing the FRP amount and the number of steel fasteners can effectively improve the flexural resistance of reinforced beam. The influence of steel fastener spacing on the bearing capacity of reinforced beam and the reinforcement design criteria are still unclear. The crack and external load have significant effects on the debonding load, material utilization rate, and failure mode of reinforced beam. The increase in the shear strength of reinforced beam mainly generated by the shear forces provided by the FRP and concrete, whereas the influence of stirrup is minimal. The increase in the FRP reinforcement amount and the decrease in the strip spacing can significantly improve the shear capacity of reinforced beam. Follow-up studies on the HB-FRP reinforcement design theory should be continued to propose calculation models for bonding characteristics considering the material and structural characteristics and develop a design method for HB-FRP steel fastener spacing based on the interfacial shear force. Furthermore, the optimized flexure and shear resistance design methods and design formulas for HB-FRP reinforced concrete beams should be developed.More>

2020, 20(6): 35-47. doi: 10.19818/j.cnki.1671-1637.2020.06.003

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Review on evaluation and optimization of light environment of extra-long urban underwater tunnel based on visual demands

DU Zhi-gang, MEI Jia-lin, NI Yu-dan, CHEN Yi-fei, TANG Zhen-nong

Abstract: To improve the traffic safety and transportation efficiency of extra-long urban underwater tunnels, the typical problems and improvement measures of light environment in extra-long urban underwater tunnels were summarized. From the aspects of comfort, economy, setting basis, and installation form, four kinds of improvement measures of light environment of tunnels were compared and analyzed, including shading facilities at the entrance, enhanced lighting at the entrance and exit, landscape decoration, and visual induction system. Drivers' visual demands were stratified according to the theory of Maslow's hierarchy of needs. The research framework of the light environment evaluation system and optimization of extra-long urban underwater tunnels was proposed, including the accident analysis, evaluation system, optimization idea, and optimization method. Analysis result shows that the light environment of extra-long urban underwater tunnels mainly has the issues of light and dark adaptation at the entrance and exit, insufficient sight distance caused by changes in the road alignment, the lack of visual reference information in the middle, and the unclear right of way in the overall space of the tunnel. The setting of a visual induction system is a low-cost and effective method to optimize the light environment, which can meet the drivers' visual differentiation needs in different tunnel sections. Drivers' visual demands can be divided into function, safety, comfort, and esthetics from low to high corresponding to the fundamental, safe, comfortable, and rhythmic visual reference systems. The evaluation system can be constructed to evaluate the light environment of extra-long urban underwater tunnels with the indexes of space right of way, human factors, driving tasks, differentiation, and rhythmicity. The light environment optimization of extra-long urban underwater tunnels should combine visual induction with enhanced lighting, while the visual induction system is mainly used to reconstruct the visual reference system. A comfortable visual reference system should be considered as the optimization target in the access zone, threshold zone, interior zone(general area), and exit zone of the tunnel, while the rhythmic visual reference system should be built in the interior reminding and awakening areas.More>

2020, 20(6): 48-61. doi: 10.19818/j.cnki.1671-1637.2020.06.004

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Control standards of rut depth based on mechanical behavior of asphalt pavement structure

CHEN Lei-lei, CHEN Dao-xie, CHEN Chao-lu, LIU Gang

Abstract: In order to further regulate the control standards of rut depth of asphalt pavement, the influence of the rut depth on the pavement structure was studied. A dynamic load calculation model of vehicle crossing the rut was established based on considering the characteristics of rut cross section, and the vehicle impact effect on the pavement structure was quantified by impact factor. The inner damage of pavement structure was studied by numerical simulation, and the degradation laws of pavement performance at different rut depths were explored. Research result shows that the impact effect of rut depth on the pavement structure cannot be ignored. The impact factor increases linearly with rut depth, and the allowable rut depth considering the impact effect should not be greater than 11 mm. The maximum tensile strain of asphalt mixture layer appears at the bottom of the upper surface layer and is positively correlated with the rut depth. While the tensile strains of the middle surface layer and lower surface layer are negatively correlated with rut depth, and their strain levels are significantly lower than that of upper surface layer. The rut depth based on the surface layer flexural failure should be less than 15 mm. The maximum shear stress appears at the bottom of the upper layer and increases gradually with rut depth. When the rut depth is between 5-10 mm, the shear stress of each surface layer changes little. When the rut depth develops from 10 mm to 25 mm, the shear stress at 0-1 cm depth of the upper layer increases by 14.5%, which is obviously faster than the decreasing rate of shear stress of the middle layer and lower layer. Thus, the rut depth based on the surface layer shear failure should be less than 10 mm. The rut depth has little influence on the tensile stress of inorganic binder stable layer. When the rut depth exceeds 15 mm, the change of compression strain on the top of subgrade should be focused to prevent large deformation.More>

2020, 20(6): 62-70. doi: 10.19818/j.cnki.1671-1637.2020.06.005

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Cumulative effect of saline construction water on engineering properties of subgrade filling material

ZHANG Sha-sha, WANG Xu-chao, YANG Xiao-hua, CHEN Wei-zhi, ZHOU Qiang

Abstract: Large-scale compression tests, salt expansion tests, and collapsibility tests were performed under the conditions of construction water with different salt addition times and types for gravelly sulfate saline soil with different sulfate salt contents. Test preparation was based on the site investigation, and samples with different types and times of saline construction water were prepared. The variation characteristics of deformation over time were observed under the condition of a 400-kPa load, single-time temperature decrease, and adding water, respectively. The influence mechanism of adding multiple times of saline construction water on the engineering properties of gravelly sulfate saline soil was analyzed. Research results show that the compression deformation of gravelly sulfate saline soil first increases and then gradually stabilizes as the times of saline construction water increases. The compression modulus shows a typical three-stage variation law, which is independent of the type of saline construction water. Under the influence of cooling, with the gradual addition of sulfate-containing construction water, the salt expansion of gravelly sulfate saline soil tends to become stable after an obvious increase, and the maximum dilatation increases by 7.9 times. The addition of chlorine-containing construction water decreases the salt expansion and then gradually stabilizes. The ultimate salt expansion was only 1/13 that of the original saline soil. Moreover, the addition of saline construction water has an obvious cumulative effect on the salt expansion characteristics of gravelly sulfate saline soil. With the increasing times of saline water additions, the collapse deformation of soil samples shows a rule of accumulation. Therefore, even if the salt content in construction water from a saline area is low, the cumulative effect from multiple uses of construction saline water is obvious and will have a negative influence on the subgrade engineering characteristics. Preventive measures should be taken during the construction process.More>

2020, 20(6): 71-81. doi: 10.19818/j.cnki.1671-1637.2020.06.006

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Four-working-platform pouring method for main arch ring concrete of rigid skeleton arch bridge

LIN Chun-jiao, ZHENG Jie-lian

Abstract: To investigate a method of setting working platforms during the concrete pouring for the main arch ring of a rigid skeleton under a reasonable stress and with a convenient and economical construction and taking the Nanpanjiang Super Long Span Bridge as an object, the transient stress variation process of rigid skeleton caused by the first ring concrete symmetrically poured from the two arch springs was analyzed. The stress process curves of the main control section of rigid skeleton were obtained. A concrete pouring method for the main arch ring was proposed with four working platforms arranged symmetrically along the longitudinal arch, and the working platforms were set at the arch spring section and the peak of control stress process curve, such that the stress increments on the rigid skeleton generated by the cocrete of two working platforms within the half span had different signs to offest part of the stress. By fitting the continuous functions of the ascending and descending sections of absolute control stress process curve, the pouring length and sequence of concrete was reasonably adjusted to reduce the transient stress and deformation of rigid skeleton. The construction operability and economy of the four-working-platform method were discussed, and the stress and deformation of rigid skeleton during the concrete pouring process for the first ring of main arch ring of Nanpanjiang Super Long Span Bridge were analyzed. Research result shows that the stress process curve of concrete filled in the arch spring tube represents a control stress and single wave curve. The proposed four-working-platform method with the order of first along the span, then in arch spring and with the length calculated by the fitting function is reasonable for the concrete pouring of Nanpanjiang Super Long Span Bridge. The maximum transient tensile and compressive stresses of rigid skeleton reduce to 0.4 and 23.5 MPa, respectively, which are well controlled within the range of material strength. The vault has no upward deflection, the maximum transient deflection and eternal ring deflection are 192 and 82 mm, respectively, and the arch axis does not deform repeatedly. The four-working-platform pouring method requires less equipment and personnel, is economical, and has good operability. It is suitable for the concrete pouring for the main arch ring of rigid skeleton arch bridges, and can be used for similar bridges.More>

2020, 20(6): 82-89. doi: 10.19818/j.cnki.1671-1637.2020.06.007

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Impact of ground motion incident angles on seismic vulnerability for bridge with thin-walled hollow tall pier

DAN De-shan, HAN Lu-lu, JU Fa-xian, DONG Jun

Abstract: A certain 4-span rigid-frame-continuous composite bridge with tall piers in western China was considered as the research object to fully assess the seismic resistance performance of long-span bridge structures with thin-walled hollow tall piers. Combined with the current bridge seismic design code, the incremental dynamic analysis method was adopted to discuss the impact of horizontal ground motion incident angle on the seismic vulnerability of bridge components based on the three-dimensional seismic vulnerability analysis method, and the influence of vertical ground motion was considered. The impact law of ground motion incident angle on the seismic vulnerability of bridge structural system was analyzed in considering the first-order reliability theory. Analysis result indicates that the bending and shearing vulnerability nephograms of the 2^# and 3^# rigid-frame piers differ significantly from the corresponding nephograms of the 1^# and 4^# cantilever piers. The bending and shearing seismic vulnerabilities of pier are not only related to the ground motion incident angle but also to the pier structural type. The distributions for the damage probability of bearings with slight, moderate, severe, and complete damage states are similar. The ground motion incident angles for the maximum damage probability are 0 and 180° when the peak ground acceleration is 0.4g. The most unfavorable incident angles for the slight and moderate damage states are 0-180° as the peak ground acceleration increases over 0.6g. The most unfavorable ground motion incident directions for the bearing deformation are mainly the longitudinal and lateral directions of the bridge. It can be seen that the damage probabilities for various damage indices of the various key components differ along with the various intensities and directions for ground motions. The number and ranges for the most unfavorable ground motion incident angles and their relative intervals of the structural system and its components with various damage indices also differ. The seismic demand for the bridge structure can not be properly evaluated by only discussing the seismic vulnerability in the longitudinal and lateral directions of the bridge. The most unfavorable ground motion incident angle and even the seismic resistance performance of long-span bridges with tall piers can be located and evaluated accurately using the proposed three-dimensional seismic vulnerability analysis method.More>

2020, 20(6): 90-103. doi: 10.19818/j.cnki.1671-1637.2020.06.008

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Fatigue assessment of joints in concrete-filled rectangular hollow section composite truss bridges based on hot spot stress method

JIANG Lei, LIU Yong-jian, LONG Xin, WANG Wen-shuai, MA Yin-ping

Abstract: In order to accurately assess the fatigue behaviour of joints in concrete-filled rectangular hollow section steel tubular composite truss bridges, the hot spot stress method was introduced. The hot spot stress range at the weld toe can be determined by the planar frame model, spatial frame model, and three-dimensional solid model. Based on 52 fatigue test data of joints, the hot spot stress range-cycle number curves were obtained through the regression analysis. A concrete-filled rectangular hollow section steel tubular composite truss bridge located at the Huangyan highway was selected as the typical case, the fatigue behaviour of the joint was assessed, and original design details were optimized. Research results show that compared with the concrete-filled rectangular hollow section steel tubular joint on the top of the pier, the hot spot stress range in the rectangular hollow section joint at mid-span is higher, which equals to 60.1 MPa, and occurs on the main surface of the chord. However, it is less than the allowable value of 71 MPa determined according to Eurcode, thereby the design of the joints met the requirements. The optimization of design details on the fatigue vulnerable joint at mid-span is carried out. After filling the hollow section with concrete, the local joint stiffness changed, resulting in a more uniform stress distribution at the weld toe intersection. The hot spot stress ranges of brace and chord surface decrease by 25.1% on average. The post-weld treatment of the original designed joint can effectively eliminate the initial tensile stress of the welding and improve the fatigue performance of the joint. The hot spot stress ranges in the brace and chord surface decreased by 14.9% on average. Using spatial frame model to assess the fatigue behaviour of optimized joint at mid-span, the maximum hot spot stress ranges on the brace and chord are 58.9 and 54.1 MPa, respectively, both less than the results of 45.2 and 47.1 MPa calculated by using the three-dimensional solid model. It demonstrats that the result obtained by using the spatial frame model is more conservative, and the fatigue effects of different hot spots can not be calculated as accurately as the three-dimensional solid model, nor can the initial position of fatigue cracking be judged accurately.More>

2020, 20(6): 104-116. doi: 10.19818/j.cnki.1671-1637.2020.06.009

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Shear performance of ultra-high performance concrete deep beams

ZHOU Jia-liang, CHEN Bao-chun, MA Xi-lun, LUO Lu-lu, HUANG Qing-wei, SU Jia-zhan

Abstract: To promote the application of ultra-high performance concrete(UHPC) deep beams, shear performance tests were conducted on four UHPC deep beams by taking the concrete strength as the main parameter, and the C40 and C80 concrete deep beams were tested for comparison. The load-deflection curves, failure modes, reinforcement strains, crack patterns and ultimate loads of UHPC deep beams were analyzed. The method specified in the Code for Design of Concrete Structures(GB 50010—2010) was used to determine the shear strengths of six deep beam specimens, to discuss whether the current method for calculating the shear capacity of ordinary concrete deep beams is applicable to UHPC deep beams. Research result shows that the greater the concrete strength is, the greater the stiffness of the deep beam under the same load is. The stiffness of UHPC specimen in its elastic stage before the cracking increases slightly with the increase of steel fiber content. Similar to the C40 and C80 concrete deep beams, the UHPC deep beams exhibit bending-shear and web-shear cracks. When the load reaches 13%-22% and 18%-34% of the ultimate load, the two types of cracks appear successively. Beam and arch stress mechanisms are both present during the loading of UHPC deep beams. The beam stress mechanism dominates the early phases of loading process, whereas the arch stress mechanism dominates the latter stages of this process. The UHPC deep beams exhibit a large number of densely and concentrated cracks and undergo shear-compression failure, without showing any cracks in the inverted arch area above their supports. In contrast, the C40 and C80 concrete deep beams undergo diagonal compression failure, and cracks appear in the inverted arch area above their supports. The shear bearing capacity of test beam increases in an approximately exponential manner with the increase of concrete strength. When the concrete strength increases from C40 to C80 and C190, the shear bearing capacity increase by 30.76% and 201.92%, respectively. When using the method specified in the Code for Design of Concrete Structures(GB 50010—2010) to calculate the shear bearing capacities of UHPC deep beams, the calculated and experimental shear bearing capacities show an average ratio of 0.89 and a mean squared error of 0.15. Therefore, this method can be temporally used to calculate the shear bearing capacity of UHPC deep beams, until a more accurate calculation method is available.More>

2020, 20(6): 117-125. doi: 10.19818/j.cnki.1671-1637.2020.06.010

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Weight limits for highway bridges under different technical condition ratings

LI Song-hui, LI Shuo, NIE Rui-feng, ZHANG Xian-tang

Abstract: In accordance with the current Code for Maintenance of Highway Bridges and Culverts(JTG H11—2004), a weight limit analysis method for reinforced concrete(RC) simply supported beam bridges was proposed by considering the actual technical condition ratings. Moreover, the typical vehicle weight limits for bridges under different technical condition ratings recommended in codes in different periods were determined. Based on the structural reliability theory and design expressions in the current code, a simplified analytical model of weight limits for highway bridges was established by taking the design live-to-dead load ratio as the fundamental parameter. The nominal resistances in the current bridge design code were used as the basis for determining the corresponding resistance correction factors for bridges under different technical condition ratings. A program for the weight limit analysis of highway bridges was used to calculate the weight limit factors of bridges under different technical condition ratings designed in accordance with the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTJ 023—85, JTG D62—2004, and JTG 3362—2018). The recommended weight limits of RC simply supported beam bridges were proposed under the assumption that the standard effect limit of design vehicle load was equivalent to the typical vehicle load effect. Analysis result shows that under the same technical condition rating and safety level, the bridge weight limits with ratings of truck-S20 and truck-20 in the JTJ 023—85 code are higher than those with safety levels of highway-Ⅰ and highway-Ⅱ in the JTG D62—2004 code, and the maximum differences are 1.2 and 5.0 t, respectively. The bridge weight limits with ratings of highway-Ⅰ and highway-Ⅱ in the JTG 3362—2018 code are significantly higher than those in the JTJ 023—85 and JTG D62—2004 codes, and the maximum differences are 13.8 and 8.6 t, respectively. Moreover, the higher the technical condition rating, the greater the difference between the bridge weight limits. The differences in the initial design resistance of bridges in codes in different periods lead to different typical vehicle weight limits under the same technical condition rating. When formulating the weight limit measures for existing bridges according to their technical condition ratings, the influences of design codes in different periods should be considered.More>

2020, 20(6): 126-134. doi: 10.19818/j.cnki.1671-1637.2020.06.011

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Corrosion damage and bearing characteristics of bridge pile foundations under dry-wet-freeze-thaw cycles in alpine salt marsh areas

FENG Zhong-ju, HUO Jian-wei, HU Hai-bo, LI Tie, YAO Xian-hua, XU Zhan-hui, WANG Fu-chun, LIU Ning

Abstract: To explore the corrosion damage characteristics of bridge pile foundation in Qinghai area under dry-wet-freeze-thaw cycles, relying on the Dexiang Expressway Project, the reinforcement and concrete specimens were embedded in the field to subjected to freeze-thaw cycles for one year. The laboratory test was used to conduct the dry-wet-freeze-thaw cycles on concrete specimens for 225 times. The variation rules of concrete mass, anti-erosion coefficient, relative dynamic elastic modulus, compressive strength, micro-mechanism and reinforcement corrosion rate at different positions and different cycle times were compared and analyzed. The numerical simulation was conducted to analyze the bearing capacity change rule of unprotected pile foundation over 20 years, and protection measurements for bridge pile foundations in alpine salt marsh areas were proposed. Research result shows that as the embedment depth increases, the correlation degree of anti-erosion coefficient of pile foundation concrete specimens in the field increases, and the maximum value is 0.93. As time increases, the maximum compressive strength loss rate of pile foundation concrete specimens is 38.20%. The areal corrosion rate of reinforcement at the depth of 0.25 m is the largest, and the value is 91%. Coating epoxy resin on the surface can effectively reduce the corrosion rate of reinforcement, The mass changes of pile foundation concrete specimen and reinforcement are not obvious. In the 225 th dry-wet-freeze-thaw cycles, the corner of pile foundation concrete specimen falls off and cracks appear around, but the mass change is small. The relative dynamic elastic modulus reduces by 39.10%, the anti-erosion coefficient reduces to 0.51, the compressive strength loss rate of concrete is 65.88%. Failare nearly occurs in the interior because of the presence of Friedel salt and other expansive substances. As the spalling thickness and corrosion depth increase, the bearing capacity of pile foundation in the first eight years remains essentially unchanged. After eight years, its bearing capacity gradually decreases. Without proper maintenance, the bearing capacity of pile foundation will reduce by 34.45% by the 20 th year. It is suggested that the key protection measures should be taken for pile foundations after 8 years of service.More>

2020, 20(6): 135-147. doi: 10.19818/j.cnki.1671-1637.2020.06.012

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Heat transfer characteristics for temperature of simple harmonic quantity in the cold-region tunnel and sensitivity of influencing factors

ZHAO Xin, ZHANG Hong-wei, YANG Xiao-hua, LAI Hong-peng, WANG Xue-ying, ZHAO Xiao-liang

Abstract: In order to investigate the spatial-temporal changing laws of temperature field in cold-region tunnels, a radial heat transfer model was established of temperature of simple harmonic quantity in the cold-region tunnel according to the time and space scales from the perspective of waves. Moreover, the radial heat transfer expression of temperature of simple harmonic quantity in the cold-region tunnel was deduced based on Fourier's laws of heat transfer. Based on the temperature test results of Xing'anling Highway Tunnel, the feasibility of the radial heat transfer expression of temperature of simple harmonic quantity was verified. Distribution characteristics of temperature of simple harmonic quantity in radial depth and its variation with freeze-thaw cycles were analyzed. The sensitivity factor for this temperature was normalized to each influence factor using the system stability analysis method. Analysis result shows that within the tunnel radial depth of 0.00-4.00 m, the temperature amplitude has a range of 11.67 ℃-0.45 ℃ and it decays as a negative exponential function. The temperature phase shift has a range of 0.00-75.24 d and it increases as a proportional function. The average annual temperature increases linearly and has a range of-0.62 ℃-1.98 ℃. Affected by the annual warming trend of temperature at the tunnel site, the average annual temperature on the tunnel wall at the entrance increases by approximately 0.75 ℃ from 2016 to 2019, which increasing every year with the freeze-thaw cycles. The average annual temperature is greatly affected by the freeze-thaw cycles within a depth of 2.00 m, but less affected at depths beyond 2.00 m. The temperature amplitude on the tunnel wall at the entrance decreases by 1.48 ℃ from 2016 to 2019, and that attenuates every year with the freeze-thaw cycles. The temperature amplitude decays faster below the depth of 2.00 m, but slower above 2.00 m. The day phase on the tunnel wall at the entrance is delayed by 7.20 d from 2016 to 2019, which continues to rise every year within freeze-thaw cycles. The sensitivities of temperature of simple harmonic quantity to each influence factor from high to low are temperature amplitude and average annual temperature of tunnel wall, ice content, water content and porosity of surrounding rock, specific heat capacity and thermal conductivity of skeleton particles.More>

2020, 20(6): 148-160. doi: 10.19818/j.cnki.1671-1637.2020.06.013

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Mixed ventilation design system combined cross passage with single shaft in extra-long highway tunnel

WANG Yong-dong, HUA Si-hao, HE Zhi-wei, TAN Zhen-jie, WANG Wei, LIU Dong-xu

Abstract: In order to reduce the construction and operation costs of highway tunnel ventilation systems, and solve the problem of limited applicable length for the complementary ventilation system, a complementary ventilation system was applied to the sectional longitudinal ventilation mode. A mixed ventilation mode combined air-exchange cross passage with a single shaft was proposed. Based on tunnel ventilation theory, the calculation formulas for this mode were deduced. Combined with tunnel ventilation design procedures, a design process from selecting the air shaft position, calculating the designed air volume, selecting the cross passage position, calculating the air exchange ratio of cross passage to checking the pollutant concentration was developed. The applicability of the mixed ventilation mode was then analyzed according to tunnel structure form and wind demand of left-right line tunnels. An engineering case study was conducted on the practicability of the mixed ventilation mode. The mixed ventilation mode was compared with the conventional sectional longitudinal ventilation mode in terms of the construction scale and operation energy consumption. Analysis result shows that compared with conventional sectional longitudinal ventilation mode, the proposed mixed ventilation mode adds two air-exchange cross passages and a smoke exhaust passage in terms of tunnel structure and reduces part of connection access and a ventilation shaft. Therefore, the overall scale of the structure and the preliminary construction cost are reduced, and the problem of complementary ventilation mode limited by the length of fire smoke exhaust in extra-long highway tunnels is effectively solved at the same time. In terms of operation energy consumption, when vehicle speed in the tunnel is 60 km·h^-1, the mixed ventilation mode is more efficient because of the utilization of the traffic wind pressure and the reduction of the need for mechanical ventilation power in the tunnel. Although the energy consumption of jet fans increases, the energy consumption of axial fans reduces by 25.00%, and the total power reduces by 10.85%. The operation energy consumption of tunnel is effectively reduced, which brings significant economic benefits.More>

2020, 20(6): 161-170. doi: 10.19818/j.cnki.1671-1637.2020.06.014

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Modeling method for non-stationary road irregularity based on modulated white noise and lookup table method

CHEN Shi-an, TONG Jia-cheng, JIANG Xu-dong, WANG Ya-xiong, YAO Ming

Abstract: To solve non-stationary problems caused by different power spectrum density(PSD) frequency structures of measured roads and vehicle speeds, a modulated white noise and lookup table based modeling methods were proposed based on an analysis of the accuracy of existing road roughness models. Combining the white noise generation method with the calculation formula of discrete PSD, a parameter setting method of Band-Limited White Noise module was developed to ensure the calculated power spectrum of road irregularity is fully consistent with the designed power spectrum.The accuracy of the proposed Band-Limited White Noise module parameter setting value was verified by comparing calculation results of white noise power spectrum density and road roughness power spectrum density according to different combinations of setting values. To solve the modeling problem of non-stationary road in spatial domain whose frequency index is not equal to 2, a road power spectrum expression was proposed, which consists of a reference item and several precision corrected items, and modulus square of modulation transfer function approximates arbitrary frequency exponent. To obtaining a frequency-time-varying input model of non-stationary road considering the influence effects of vehicle speed change in time domain, a lookup table operation was used to obtain time-domain non-stationary road irregularity derived from time-varying vehicle speed based on a fixed spatial road irregularity. The superiority of the proposed modeling methods was verified by applications of spatial-domain non-stationary road irregularity modeling and non-stationary road irregularity modeling considering time-varying vehicle speed. Research result shows that the power spectrum density curves of road irregularity in spatial domain constructed by modulated white noise based non-stationary road irregularity modeling method agree well with the designed objective curves in the application examples. The non-stationary problem of road irregularity caused by time-varying vehicle speed is effectively solved by using the lookup table method.More>

2020, 20(6): 171-179. doi: 10.19818/j.cnki.1671-1637.2020.06.015

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Zonal modeling method for mass flow of large-scale marine compressor

SHEN Hao-sheng, ZHANG Jun-dong, YANG Bo-cheng, JIA Bao-zhu, GAN Hui-bing

Abstract: To address the problems of unreliability of extrapolation when using a look-up table and inconsistent accuracy in prediction and extrapolation when using a single curve-fitting method in different operating zones of a compressor, a zonal modeling method was proposed for the mass flow of a large-scale marine compressor. After a zone division function was defined, the entire operating area of compressor was divided into the design, low-speed, high-speed, and low-pressure ratio zones. Following a comparison and analysis of the accuracies of prediction and extrapolation with the classical and proposed compressor mass flow models, a mathematical model with the highest accuracy was selected for each zone. A curve blending method was adopted to guarantee a smooth transition of the iso-speed line to prevent the possible discontinuity when the operating point enters the low pressure ratio zone from other operating zones during the dynamic simulation process. To validate the correctness and effectiveness of the proposed modeling method, it was applied to the simulation experiment of a large-scale low-speed two-stroke marine diesel engine model conducted under steady and transient operating conditions. Research result shows that compared with the look-up table method, the proposed modeling method can effectively improve the steady-state prediction accuracy of turbocharger rotational speed for the main engine simulation model, while reducing the mean absolute percentage error from 3.54% to 0.61%. The operating point of compressor can transition steadily and continuously from the design operating zone to the non-design operating zones under the transient operating condition when the speed and load of main engine change. The proposed modeling method not only accurately predicts the existing sample data points in the design operating zone of compressor, it also reasonably and robustly extrapolates the data to the non-design operating zones. The method can be applied directly to dynamic simulation research of turbocharged engines, and can be used to generate the compressor performance map for the full range of operating conditions offline. Accordingly, the method can be used in commercial engine performance simulation software.More>

2020, 20(6): 180-196. doi: 10.19818/j.cnki.1671-1637.2020.06.016

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Vehicle driving cycle construction method of urban roads

GUO Jia-chen, JIANG Heng, LEI Shi-ying, ZHONG Zhi-rong, ZUO Hong-fu, XU Juan

Abstract: In order to optimize vehicle driving performance, test cycles reflecting actual road driving cycles in China were constructed. Taking the measured road data of light-duty vehicles as the data source, the vehicle driving cycle construction method of urban road was proposed. Data collection covered the main period and roads, the abnormal data were eliminated, and the multi-scale wavelet transform was introduced to reduce the noise of vehicle speed. Three-layer wavelet decomposition was used to filter the impact of ground disturbance, and the key information of vehicle speed was retained. The car kinematics segment feature system based on 9 representative characteristic parameters closely related to the driving characteristics was established. Principal component analysis and auto-encoder were used to reduce the dimension of features. K-means++clustering algorithm was used to determine the kinematics segments and the Silhouette function was introduced to filter the clustering results to replace manual selection, and determine the number of clusters of 2 categories. The distance from the corresponding cluster center was used as an indicator, 200 kinematic segments in each category that can best reflect the characteristics of the category were selected as the candidate kinematic segments. Finally, the representative kinematic segments were determined based on the minimum performance value evaluation method, the construction of vehicle driving construction was finished, and the corresponding vehicle driving cycles curves based on principal component analysis and auto-encoder were obtained respectively. Calculation results show that vehicle driving cycle construction based on principal component analysis and auto-encoder is highly representative and reasonable according to the data source. The absolute valves of relative errors between the data based on principal component analysis and the data source are mostly less than 10%. The relative errors of average speed, average driving speed, idle time ratio, acceleration time ratio, deceleration time ratio, average acceleration, acceleration standard difference, and average deceleration are 0.75%, 5.50%, 9.14%, 9.80%, 9.98%, 8.45%, 6.17% and 7.73%, respectively. Only the relative error of velocity standard deviation reaches 24.31%. Therefore, the principal component analysis has stronger comprehensive advantages than the results obtained by the auto-encoder method, and it is more suitable for vehicle driving condition construction.More>

2020, 20(6): 197-209. doi: 10.19818/j.cnki.1671-1637.2020.06.017

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Statistical approach for the region-oriented volume of freight transport on highway

YAN Sheng-yu, XIAO Run-mou, YANG Ming

Abstract: The concept of region-oriented freight transportation volume was proposed. Non-commercial trucks and nonlocal trucks were included in the statistics category of the region-oriented freight transportation volume, and the basic data sets were summarized. The factors of the registration place, usage, level of the highway network, and traffic flow direction of the vehicles were analyzed. Statistical thoughts and splitting logic of the freight transportation volume, and statistical models of freight volume and freight turnover volume were developed. Based on the freight volume of registered local commercial trucks, a scale index of region-oriented freight volume was created and used to evaluate the relative offset degree and involvement of nonlocal trucks. Analysis results show that when the limit error is controlled within 10%, the region-oriented freight volume can be evaluated exactly by five basic data sets: special survey data on freight transport, expressway network toll collection data, sample survey data of highway, traffic volume survey data of highway, and truck data in the register of vehicle management. For the studied city, the proposed statistical model embodies a 0.45% relative deviation rate of the freight turnover to create GDP per ten thousand yuan with the national average level, which is consistent. The scale index of region-oriented freight volume is 2.47, which indicates that nonlocal trucks involved in local freight transportation to a high degree in cities with developed real economy. The freight transportation volume of commercial trucks registered at the local government office is not sufficient to support economic planning. However, a lack of registered trucks does not indicate an insufficient transportation capacity. The commercial trucks registered locally mainly undertake short-distance freight transportation, which accounts for 66.28% of the total in-city freight volume. Nonlocal trucks mainly undertake inter-city and inter-provincial goods, which accounts for 79.16% of the total volume. In the near future, when trucks are charged by vehicle type, the average load of each vehicle type and the rate of each loaded truck in total will be key parameters for the evaluation of the region-oriented freight transportation volume. In addition, inter-provincial disequilibrium existed in the traffic volume of trucks with 3 axles or more.More>

2020, 20(6): 210-217. doi: 10.19818/j.cnki.1671-1637.2020.06.018

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Multi-objective optimization method of air route space-time resources allocation

TIAN Wen, YANG Fan, YIN Jia-nan, SONG Jin-jin

Abstract: To improve the degree of collaborative decision-making between airlines and air traffic controllers, as well as reduce the level of flight delays, air route flights were used as a research object and the multi-objective allocation of route space-time resources was studied. The effects of uniqueness, time sequence, and feasibility constraints of flights under actual operating conditions were considered and the flight trajectory and entry time slot assigned by the flight in the restricted area were viewed as decision variables. The lowest total flight delay cost and the lowest airline delay fair loss deviation coefficient were regarded as objective functions. A multi-objective nonlinear 0-1 integer programming model was constructed. Based on the characteristics of the model reference, the non-dominated sorting genetic algorithm-Ⅱ(NSGA-Ⅱ) was used and an integer gene encoding scheme was designed by the permutation encoding method. A feasible solution set was generated to maximize genes. To verify the validities of the model and algorithm, based on the South China sea area flight operation example, the performance of searching for the optimal solution was studied and the algorithm was compared with the traditional ration-by-schedule(RBS) method. Research result shows that the improved encoding style of the NSGA-Ⅱ algorithm makes the generation distance of the solution set population converge from 600 to 30 and becomes stable after approximately 50 generations, with suitable convergence. The Pareto solution set with six solutions is generated for the multi-objective optimization model, with a 66.7% probability that the RBS method is completely dominated by the results. The average flight delay cost in the optimization results is 8.5% lower than that of the RBS method, and the average fair loss deviation coefficient is 70.6% lower. The implementation effect of the multi-objective optimization method for the space-time resources of the air route is remarkable. The fairness of each airline can be considered on the basis of reducing the total delay cost, making this an effective method for solving the problem of flight trajectory and slot resource allocation.More>

2020, 20(6): 218-226. doi: 10.19818/j.cnki.1671-1637.2020.06.019

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Real-time identification method of abnormal road driving behavior based on vehicle driving trajectory

LU Jian, WANG Ke, JIANG Yu-ming

Abstract: To improve the active prevention and control of road traffic safety, the driving trajectory data of cars were used as the research object and the real-time identification problem of abnormal driving behaviors was studied. A massive amount of vehicle driving trajectory data was extracted based on an unmanned aerial vehicle recorded traffic video. The theory of applying the measurement of risk to quantify the typical abnormal driving behaviors was proposed. A large-sample statistical distribution method was used to determine the characteristic value thresholds for abnormal driving behaviors. The abnormal driving behavior spectrum was established and combined with the traffic environment information. The characteristic value of the abnormal driving behavior spectrum was calculated. Based on the characteristic value of the vehicle's abnormal driving behavior spectrum, the abnormal vehicle samples were labeled. The driving behavior spectrum parameters were partially used as input and imbalanced class boosting artificial intelligence algorithms were used to establish an abnormal driving behavior identification model. To verify the effectiveness of the method, vehicle driving trajectory data were collected using an unmanned aerial vehicle traffic video in Shanghai, and the characteristics of car abnormal car-following behavior were analyzed. Research result shows that the threshold of the abnormal car-following characteristic parameter is 0.19 s^-1 using the interquartile range method, most of the samples are in the normal car-following state, and about 2% of the samples are in the abnormal car-following state. Based on the ratio of the normal car-following state and the abnormal car-following state in the driving trajectory of each car, a 95% percentile is used to divide the examples of 8 917 cars into 445 abnormal car-following cars and 8 472 normal car-following cars. The imbalanced class boosting algorithm CUSBoost achieves a recall rate of 94.4% and a precision rate of 85.9% in identifying abnormal car-following vehicles. Its balanced score and the area under the precision-recall curve are the highest among all algorithms. As an objective and quantitative expression method of abnormal driving behavior, the abnormal driving behavior spectrum can be combined with the artificial intelligence method to generate a massive library of abnormal driving behaviors. The imbalanced class boosting algorithm can address the imbalance problem of abnormal driving behavior data and has a better ability to identify abnormal driving behaviors compared to conventional algorithms.More>

2020, 20(6): 227-235. doi: 10.19818/j.cnki.1671-1637.2020.06.020

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Abnormal road driving behavior spectrum establishment and characteristic value calculation method based on vehicle driving trajectory

WANG Ke, LU Jian, JIANG Yu-ming

Abstract: To quantitatively describe the dynamic change process of driving behavior and the degree of abnormal driving under different road driving scenarios, the establishment and analysis methods of abnormal driving behavior spectrum were studied. The driving behavior spectrum based on the key parameters of vehicle driving trajectory was established. The measurement of risk method was applied to quantify four types of abnormal driving behaviors, including abnormal car-following, serpentine driving, speed instability, and abnormal lane-changing. An abnormal driving behavior spectrum was established based on the driving behavior spectrum. Traffic flow conditions were divided based on the traffic volume-density relationship and the differences among the statistical parameters of driving behavior. Under different traffic flow conditions, the thresholds of the characteristic parameters of abnormal driving behaviors were determined by using the interquartile range method. The abnormal driving behavior scores of each driver were calculated based on the characteristic parameter thresholds. The weights of abnormal driving behaviors were determined by using the CRITIC weighting method and the characteristic values of the abnormal driving behavior spectrum for each driver were calculated. To verify the effectiveness of the method, vehicle driving trajectory data were collected by an unmanned aerial vehicle traffic video in Shanghai and the characteristics of car abnormal driving behavior were analyzed. The characteristic values of the abnormal driving behavior spectrum were verified by the expert scoring method. Analysis result shows that the traffic flow condition clustering method based on driving behavior parameters divides the traffic flow condition of data into three categories: free flow, saturated flow, and congested flow. The clustering method is more suitable for driving behavior analysis than the traffic flow condition division method based on the fundamental diagram. The characteristic parameter distributions of abnormal car-following, serpentine driving, and speed instability under different traffic flow conditions are significantly different. The occurrence of extreme values of abnormal car-following, serpentine driving, and speed instability under congested flow conditions is more frequent, while the abnormal lane-changing characteristic parameter has a similar distribution under each traffic flow condition. The thresholds of serpentine driving, speed instability, and abnormal lane-changing increase with the increase of traffic flow density. The weights of abnormal car-following, serpentine driving, speed instability, and abnormal lane-changing calculated by the CRITIC weighting method are 0.19, 0.33, 0.37, and 0.11, respectively. The distribution ranges of the abnormal driving behavior spectrum characteristic values under free flow, saturated flow, and congested flow are similar, all between 0 and 0.4. The expert's abnormal driving behavior evaluation is consistent with the abnormal driving behavior spectrum characteristic values. The establishment of an abnormal driving behavior spectrum and the calculation method of characteristic values can automatically identify abnormal drivers by using the vehicle driving trajectory data. The method is objective, adaptable, and reliable, and can detect abnormal drivers in time, providing drivers with safety tips and technical support for traffic safety early warning to traffic management departments.More>

2020, 20(6): 236-249. doi: 10.19818/j.cnki.1671-1637.2020.06.021

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Automatic crack detection algorithm for airport pavement based on depth image

LI Hai-feng, WU Zhi-long, NIE Jing-jing, PENG Bo, GUI Zhong-cheng

Abstract: To detect small cracks in airport pavements under strong noise, weak illumination and low contrast, a crack detection algorithm for airport pavements based on depth images was designed. The collected depth image was divided into multiple grids, and each grid was expanded to obtain a local pavement region. For each grid region, the random sampling consensus algorithm was used to construct and optimally estimate the local cubic curved surface. On this basis, the global curved surface model of the entire image acquisition region of parement was generated by fusing the curved surface models of all grid regions under the global scale. Based on the difference image between the global curved surface model and the original depth image, candidate crack pixels were segmented by the adaptive threshold method, and various morphological constraints, such as the total number, length and length width ratio of crack pixels were used to screen the candidate crack pixels to eliminate the incorrect candidate crack pixels, so as to obtain the final crack detection results. The experiment was carried out on the airport pavement depth image datasets. The manual annotation results were taken as the ground truth. The accuracy, recall rate and F value were used as the quantitative evaluation indices. The proposed algorithm was compared with four representative traditional algorithms. Experiment result shows that the highest accuracy, recall rate and F value of the traditional algorithm are 77.05%, 41.02% and 50.02%, respectively. The proposed algorithm has obvious advantages in the accuracy, recall rate and F value, with average values of 91.20%, 97.99% and 94.12%, respectively. The proposed algorithm can detect the crack with the minimum width of 3 mm and the minimum length of 10 cm in the depth image with a resolution of 1 984×2 000, and realize the target of detecting small cracks in the complex airport pavement scene.More>

2020, 20(6): 250-260. doi: 10.19818/j.cnki.1671-1637.2020.06.022

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