交通运输工程学报

Cover and Contents of Vol.24, No.3, 2024

Cover Contents

Review on long-life design theory for bridges

LIU Yong-jian, LIU Jiang, ZHOU Xu-hong, WANG Zhuang, MENG Jun-miao, ZHAO Xin-dong, YANG Jian, GHOSN Michel

Abstract: To promote the development of long-life design theory for bridges, the service life of bridges and the influencing mechanisms were studied, the current research status and main problems faced in the long-life design of existing bridges were summarized, and the future research focuses and directions were discussed. Research results show that current specifications in different countries determine the design life of bridges based on bridge importance and highway class, and they follow a variable life design idea to assign different design lives to bridge elements and components with different functions, importances, and replacement difficulties. The life of a bridge depends on its long-term performance in the actual service environment, including durability under environmental erosion, fatigue under repeated loading, and creep property under sustained loading, and it is significantly influenced by the service environments, maintenance interventions, and construction processes. The research on long-life technologies for new bridges mainly focuses on design methods and high-performance materials. Existing service life and durability design methods mainly study environmental actions, degradation mechanisms, material performances, construction control, and inspection management, achieving the design goal of "deemed-to-satisfy", but they do not achieve improvement on the probabilistic level and quantification of design life. The life cycle design still remains at the conceptual level. The application of high-performance materials, such as ultra-high performance concrete (UHPC), weathering steel, and fiber reinforced polymer (FRP), is an effective way to improve the design life of bridges. In order to establish a systematic theory system for the long-life design of bridges, future research should adhere to the basic framework of long-life design, including defining structural positioning, improving performance indicator system, optimizing initial structural condition, improving service micro-environment, and controlling degradation transmission paths. Research should also be conducted on the identification and regulation of long-life genes of bridge structures, evolutionary laws of bridge micro-environments in the life cycle, and fully probabilistic quantification design methods for the service life of bridges.More>

2024, 24(3): 1-24. doi: 10.19818/j.cnki.1671-1637.2024.03.001

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Review on deterioration behavior and life extension technologies of cement pavement in service

LI Sheng, ZHANG Hai-tao, SUN Yu, LIU Ya-ru, YU Shi-qing, WANG Miao, ZHANG Zong-shuai

Abstract: In order to improve the durability and service life of cement pavement in service, the mechanical response and fatigue damage evolution behavior of cement pavement structure were reviewed based on the research status of life extension repair technologies of cement pavement in China and abroad. The formation mechanism of main diseases, deterioration behavior, and characteristics of cement pavement were analyzed, and the research progresses of different deterioration behavior control technologies were summarized. Based on the idea of making full use of the residual bearing capacity of old cement pavement slabs and the research of the mechanical behavior of old cement pavement with overlay structure for life extension, a typical overlay structure of separated continuous reinforced concrete (CRC) slabs under harsh environment was proposed. The perceptive technology of service behavior of cement pavement structure was summarized. Research results show that the establishment of a mechanical model accurately reflecting the service behavior of cement pavement can provide a scientific theoretical basis for its reasonable design and accurate life prediction. Evaluating and repairing the technical condition of cement pavement in time at the initial stage of damage can extend its service life to a certain extent. Joint load transfer capacity and void beneath the slab are significant factors affecting the durability of cement pavement, which should be paid more attention in the repair process of old cement pavement. Overlaying asphalt concrete and cement concrete on old cement pavement is an effective measure to extend its life. In terms of whole life-cycle, overlaying CRC slabs is an effective technical means to extend the life of cement pavement in service with heavy traffic. In the future, a life prediction theory should be established by considering the deterioration behavior and residual strength of cement pavement in service, and high-performance, compatible, and environmentally friendly materials for life extension and repair of cement pavement should be developed. With the help of the perception and processing technologies of multi-source heterogeneous big data of service performance, the theoretical technology and industry norms of overlay structure design of cement pavement in service should be improved, and the service level and service life of cement pavement in service are comprehensively improved.More>

2024, 24(3): 25-47. doi: 10.19818/j.cnki.1671-1637.2024.03.002

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Research progress on strength enhancement measures of emulsified asphalt cold recycled mixtures

WANG Hai-nian, JIAO Hu, XU Ning, CHEN Yu, LI Yuan-le

Abstract: The strength formation process and composition mechanism of emulsified asphalt cold recycled mixtures were analyzed. The measures to improve the strength of emulsified asphalt cold recycled mixtures were summarized from four aspects, including addition of additives, optimization of binding materials, improvement of design methods and construction processes, and reclaimed asphalt pavement (RAP) pretreatment. The enhancement mechanism and improvement effect of various measures were analyzed and compared. According to the problems and characteristics of various measures, corresponding application suggestions were put forward, and future research directions were foreseen. Analysis results show that the addition of additives to enhance the strength has been relatively well studied, followed by the optimization of binding materials, and less research has been done to improve mixture design methods and construction processes, as well as RAP pretreatment, however, these aspects have promising applications for increasing the strength of the mixture. Among the additives, cement is the most commonly used and systematically studied, and its enhancement effect is better than that of lime, but too high cement content will lead to insufficient crack resistance at low temperatures. Volcanic ash material also suffers from this problem and has more impurities. Fiber has a more balanced improvement effect, but is affected by the type, doping amount, adding order, and other factors. Regenerating agent can improve durability, but is not favorable for early strength. In terms of binding material, the slow cracking nature of emulsified asphalt contributes to the overall strength, high viscosity and fast setting are beneficial to early strength, and the doping amount should be moderate and recommended at 3.5%-4.0%. Modified emulsified asphalt should be selected according to specific climatic and environmental conditions. The mixture design methods and construction processes are mainly improved in terms of the aggregate, moisture content, structural layer thickness, mixing sequence, and compaction and curing methods, with a slight strength enhancement effect, which can be used as an additional improvement condition. The trend of using large amounts of RAP makes RAP pretreatment technology more important, which currently focuses on four aspects: reduction of agglomeration rate, grading classification, strict control of RAP storage conditions, and chemical modification of RAP surface. Future research should be conducted in the following aspects: further clarifying the interaction mechanism between volcanic ash materials and emulsified asphalt to determine the optimal doping amount and remove impurities, exploring the joint application of different additives and different modifiers in improving the strength of the mixture, investigating the improvement effect of multiple enhancement measures according to the strength formation mechanism to obtain a balanced system of strength enhancement measures, focusing on the pretreatment means of RAP, and exploring the enhancement mechanism and effect of RAP surface physical properties pretreatment on the strength of emulsified asphalt cold recycled mixtures.More>

2024, 24(3): 48-68. doi: 10.19818/j.cnki.1671-1637.2024.03.003

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Life-cycle economic evaluation model of long lasting weathering steel bridges

WANG Chun-sheng, ZHANG Jing-wen, TAN Chen-xin, DUAN Lan, WANG Yi-wei

Abstract: Based on the life-cycle cost analysis theory of bridges, the cost characteristics of long lasting weathering steel bridges at different stages were systematically summarized, and the contents and characteristic parameters of the life-cycle economic evaluation of long lasting weathering steel bridges were clarified. Also, the basic assumptions for cost calculation of long lasting weathering steel bridges were provided. Two cost calculation methods at construction and operation stages were analyzed by comparing the cost difference between uncoated weathering steel bridges and coated steel bridges, and a life-cycle economic evaluation model of long lasting weathering steel bridges was established. Three long lasting uncoated weathering steel composite bridges in China were taken as examples to calculate the life-cycle cost of bridges at each stage. The economic parametric influence of coating and maintenance methods on the life-cycle cost of long lasting weathering steel bridges was clarified, and the economic advantage of the life-cycle cost of long lasting uncoated weathering steel bridges was analyzed. Research results show that the cost difference between uncoated weathering steel bridges and coated steel bridges mainly lies in the prices of steel and welding materials, patina detection cost, coating maintenance cost, and resulting environmental and user cost. Compared with four coated steel bridges, the cost of uncoated weathering steel bridges reduces by 11%-21% in the life-cycle, and they have significant economic advantages throughout the life-cycle. Washing cycle has a significant influence on cost that increases by 5%-11% throughout the life-cycle when the cycle changes from once every six years to once every year. When the coating area of uncoated weathering steel bridges reaches about 70%, their life-cycle costs are greater than that of coated steel bridges. The life-cycle economic evaluation model of long lasting weathering steel bridges can provide a basis for bridge scheme design and analysis of techno-economic cost performance, which will promote the promotion and application of long lasting weathering steel bridges.More>

2024, 24(3): 69-81. doi: 10.19818/j.cnki.1671-1637.2024.03.004

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Shear bearing capacity calculation method for UHPC beams with steel bottom plate

YAN Ban-fu, LIU Qian, WANG Kai, TU Bing, KE Lu

Abstract: To investigate the shear performance and the calculation method for the shear bearing capacity of ultra-high performance concrete (UHPC) beams with steel bottom plates, seven test UHPC beams were designed and fabricated for shear-resistance testing by test research and theoretical analysis, with test parameters including joint configuration, longitudinal web reinforcement layout, and shear span ratio. Combined with limit equilibrium theory and sub-item linear superposition, a recommended formula for calculating the shear bearing capacity of UHPC beams with steel bottom plates was established. Shear contributions from stirrups, steel fibers, UHPC matrix, and steel plates were considered in this formula. It was subsequently compared with the calculation formula prescribed by the French code. Test results show that the failure mode of joint beams is characterized by shear failure with joint malposition, with primary cracks progressing diagonally along the joint side near the mid-span. In contrast, the failure mode of intact beams is related to the shear span ratio, shifting from shear-compression failure to flexural-shear failure as the shear span ratio increases. The presence of joints reduces the shear bearing capacity of UHPC beams with steel bottom plates, and it decreases with the increase of the shear span ratio. The layout of longitudinal web reinforcement can improve the shear bearing capacity and deformability of these beams effectively. The average ratio of the calculated value of shear bearing capacity via the proposed method to the test value is 0.91, with a coefficient of variation of 0.16. In comparison, the average ratio of the calculated value of shear bearing capacity via the French code method to the test value is 1.08, with a coefficient of variation of 0.29. Therefore, the proposed calculation method exhibits lower discreteness and is applicable for the shear bearing capacity calculation of UHPC beams with steel bottom plates.More>

2024, 24(3): 82-93. doi: 10.19818/j.cnki.1671-1637.2024.03.005

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Flexural capacity of steel reinforced ultra-high performance concrete beams with rectangular section

LIN Shang-shun, JI Bang-chong, LIU Jun-ping, LIN Jian-fan, ZHAO Jin-bing

Abstract: To study the bending resistance characteristics of steel reinforced ultra-high performance concrete (SRUHPC) beams with rectangular section, four SRUHPC beam specimens with rectangular section were fabricated, with the reinforcing ratios ranging from 0.8% to 1.1% and the steel ratios ranging from 8.7% to 15.6%. The embedded steels are I-shaped, inverted T-shaped, and H-shaped. Flexural ultimate capacity tests were conducted to analyze the damage mechanism and failure modes of SRUHPC beam specimens with rectangular section. Based on test results and theoretical derivations, a calculation method for the flexural capacity of SRUHPC beam with rectangular section was proposed. The flexural capacities of 21 SRUHPC beam specimens with rectangular section and 111 finite element calculation models were calculated, and the calculation results were compared with the test and finite element calculation values. Analysis results indicate that the failure modes of SRUHPC beam specimens with rectangular section are all reinforced failures due to bending. The steels and longitudinal tensile reinforcements yield successively, followed by the crushing of the UHPC in the compression zone. The steels and UHPC work well together until the specimens failure. The specimens with embedded inverted T-shaped and H-shaped steels exhibit higher capacities and stiffnesses compared to those with embedded I-shaped steel, and they demonstrate better crack resistances. Compared with other specimens, under the same load, the strains and strain development rates of longitudinal reinforcements, UHPC, and steels in specimens with embedded H-shaped steels are relatively smaller. Therefore, setting upper and lower flanges in the steel within SRUHPC beam with rectangular section contributes to enhancing the flexural performance of the composite beam. The calculated results obtained by the proposed method show mean ratios of 0.972 and 1.035 compared with the test and finite element calculation values, with variances of 0.009 and 0.002, respectively. The research results can provide theoretical supports for the promotion and application of SRUHPC beams with rectangular section in practical engineering and the formulations of codes and regulations.More>

2024, 24(3): 94-109. doi: 10.19818/j.cnki.1671-1637.2024.03.006

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Equivalent method for designed earthquake-induced track geometric irregularities on high-speed railway bridges

YU Jian, ZHOU Wang-bao, JIANG Li-zhong, FENG Yu-lin, LIU Xiang

Abstract: In order to solve the equivalent problem of designed earthquake-induced track geometric irregularities considering structural randomness, a numerical simulation model of high-speed railway track-bridge system was established. Based on the short-time Fourier transform and the hypothesis testing principle, designed earthquake-induced track geometric irregularities were constructed. The equivalent fitting models and equivalent amplitude response spectra of designed earthquake-induced track geometric irregularities were established. A method for correcting the equivalent amplitude response spectrum considering structural randomness was proposed, and the rationality of the equivalent method for designed earthquake-induced track geometric irregularities was evaluated by comparing to measured geometric track irregularities after earthquake. Analysis results show that the fitting errors of designed earthquake-induced track geometric irregularities can be controlled below 10% under different pier height conditions by the combination of sine function and linear function. When the correction coefficients under seismic fortification and rare earthquakes are set to 3.0 and 1.5, the applicability of the modified fitting model obtained by multiplying the equivalent fitting model and the correction coefficient to random structures can meet the requirements. There is not significant difference in the shape and amplitude of measured geometric track irregularities before and after earthquake, and the corresponding amplitude error of lateral vehicle body acceleration is less than 5%. When the earthquake intensity is low, train can operate normally without significant deceleration. Compared with the measured geometric track irregularities after earthquakes, designed earthquake-induced track geometric irregularities increase the amplitude of lateral vehicle body acceleration by nearly 50%, and the driving speed threshold after earthquake calculated based on designed earthquake-induced geometric track irregularities has a reasonable safety margin. The established equivalent method for designed earthquake-induced track geometric irregularities on high-speed railway bridges can provide a fast and accurate manual calculation method for determining the driving speed threshold after earthquake and earthquake-resistant design based on driving performance after earthquake.More>

2024, 24(3): 110-123. doi: 10.19818/j.cnki.1671-1637.2024.03.007

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Seismic performance of steel strip reinforcement measure on double-arch tunnel with thin and straight mid-partition wall

WANG Ming-nian, LI Ze-xing, TANG Lang-zhou, YU Li, LU Ming

Abstract: The Ningqiao Tunnel project was taken as the research object, and a three-dimensional dynamic time-history numerical calculation model was established in FLAC3D based on seismic vulnerability analysis method. The full-process automation calculation of the incremental dynamic analysis method in seismic vulnerability analysis was achieved through secondary development by Python. The vulnerability curves of the double-arch tunnel structure with thin and straight mid-partition wall under the eight different combinations of factors were given, including the measures with and without steel strip reinforcement, two directions of seismic wave incidences (horizontal and vertical directions), and two types of surrounding rock grades (Ⅳ and Ⅴ grades). According to the vulnerability curves, the damage probabilities of the structure at the tunnel site under seismic fortification intensity were obtained. The seismic performance and the pattern of steel strip reinforcement measures were evaluated by comparing the damage probabilities. The actual effect of steel strip reinforcement measures was verified by comparing the failure patterns and damage degrees of similar model structures with and without seismic measures based on a large-scale shaking table test. Research results show that regardless of the factor combination, the steel strip reinforcement measures can effectively reduce the damage probabilities of the structure in different damage states. The effectiveness is significantly influenced by the surrounding rock grade but less by the direction of seismic wave incidence. Under the Ⅴ grade surrounding rock condition, the probabilities of slight, moderate, and severe damages reduce by 51.94%, 41.29%, and 29.63%, respectively when the seismic waves are incident in the horizontal direction, and reduce by 55.68%, 48.32%, and 35.29%, respectively when the seismic waves are incident in the vertical direction. Under the Ⅳ grade surrounding rock condition, the probabilities of slight, moderate, and severe damages reduce by 16.45%, 11.19%, and 7.11%, respectively when the seismic waves are incident in the horizontal direction, and reduce by 12.23%, 9.45%, and 7.49%, respectively when the seismic waves are incident in the vertical direction. In the shaking table test, the damage degree of the similar model structure with steel strip reinforcement measures under the most unfavorable factor combination is significantly lower than the structure without seismic measure. The steel strip reinforcement measures can effectively reduce the number of diseases, lower the degree of structural damage, and enhance the seismic performance of the structure by improving the overall load-bearing capacity of the structure.More>

2024, 24(3): 124-138. doi: 10.19818/j.cnki.1671-1637.2024.03.008

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Adhesion/cohesion failure behavior of porous asphalt concrete considering mortar random distribution

WANG Xiao-wei, ZHANG Yi-ming, WANG Xing-wei, REN Jia-xing, YANG Xu, WONG Yiik-diew, WANG Hai-nian

Abstract: A meso-scale finite element modeling method for incorporating the random distribution of mortar was proposed to obtain a more realistic adhesion/cohesion failure behavior of porous asphalt concrete (PAC). The actual meso-structure and mortar distribution of PAC were quantified by using X-ray CT scanning and image processing technology, and the random distribution characteristics of mortar were evaluated. The adhesion/cohesion properties of mortars with different thicknesses were evaluated by pull-off test that can accurately control the thickness of mortar, and the cohesive zone model parameters corresponding to different thicknesses of mortar were determined. Zero-thickness cohesive elements were embedded at the mortar-aggregate interface and within the mortar, and corresponding model parameters were assigned to the cohesive elements based on the mortar thicknesses in different regions of PAC. Finally, a meso-scale finite element model considering mortar random distribution (Model A) was built to study the meso-scale evolution process of PAC adhesion/cohesion failure behaviors. Research results indicate that it is recommended to divide the specimens into 36 parts to characterize the random distribution characteristics of mortar. Mortar thickness has significant influences on PAC adhesion/cohesion properties, failure modes, and cohesive zone model parameters. Adhesion failure is observed when the mortar thickness is less than 0.9 mm or between 1.2-1.8 mm, while adhesion-cohesion mixed failure occurs when mortar thickness exceeds 1.9 mm, and other mortar thicknesses result in cohesion failure. Adhesion/cohesion strength increases with increasing mortar thickness in the same failure mode. Compared with the meso-scale finite element model without considering mortar random distribution (Model B), the crack initiation points of Model A and Model B are both adhesion failures, but failure locations are different. Model B primarily exhibits a single adhesion failure, while Model A demonstrates multiple adhesion/cohesion failure behaviors, which is more consistent with field complex adhesion/cohesion failure behaviors. The random distribution of mortar has significant influences on the adhesion/cohesion failure process, stress distribution, and crack propagation of PAC. Therefore, considering the random distribution of mortar can more accurately identify the weakest position of PAC adhesion/cohesion failure, and increasing the mortar thickness can delay the evolution of adhesion/cohesion failure.More>

2024, 24(3): 139-153. doi: 10.19818/j.cnki.1671-1637.2024.03.009

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Pavement surface distress detection in complex scenarios driven by multi-dimensional image fusion

GUAN Jin-chao, DING Ling, YANG Xu, LIU Peng-fei, WANG Hai-nian

Abstract: To improve the accuracy and robustness of crack and pothole detection of pavement surface in complex scenarios, the morphological irregularity of pavement surface distresses and the influence of environmental noises in practical detection scenarios were considered, and an automatic pavement surface distress segmentation model and feature fusion optimization method for multi-dimensional images were proposed. Based on high-precision pavement surface point cloud models reconstructed by multi-view stereo vision, 2D and 3D images were generated by the rasterization of homologous point clouds. The pavement surface distress image dataset in complex scenarios was established. A lightweight encoding-decoding network, namely PDU-net, integrating depthwise separable convolution and multi-layer feature combination, was developed for pixel-level crack and pothole detection. Based on the segmentation model, two multi-dimensional image fusion strategies, including pixel operation and channel recombination, were proposed to improve the extraction efficiency of deep learning networks in shallow and fine crack features. Experimental results show that the PDU-net model can effectively learn features from different types of images and distresses. The training loss of the PDU-net on different datasets can converge stably, with the training cycles of 3D images shorter than that of 2D images. Compared with existing convolutional segmentation networks, the PDU-net model achieves higher accuracy and efficiency for pavement surface distress segmentation in complex scenarios. The harmonic means of 3D crack and pothole image segmentation are 81.00% and 95.85%, respectively. The average forward inference time of the PDU-net is about 30% of the existing models. The segmentation accuracy and robustness of complex cracks can be improved by multi-dimensional fusion images. When the optimal color-depth ratio is 0.2, the harmonic mean of the crack segmentation increases to 83.31%. In conclusion, the proposed method can effectively suppress environmental noises and strengthen the surface distress features in complex scenarios.More>

2024, 24(3): 154-170. doi: 10.19818/j.cnki.1671-1637.2024.03.010

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Mechanical properties of composite improved phyllite soil under uniaxial compression

ZHAO Xiu-shao, CHENG An, ZHAO Lin-hao, DENG Qi, ZHOU Zhi-jie, RAO Jiang-long

Abstract: To address the issue of insufficient strength of phyllite soil as a subgrade filler, a composite improvement method using cement and red clay to improve phyllite soil was proposed. Through unconfined compressive strength tests, the stress-strain curves of composite improved phyllite soil under soaked and unsoaked conditions were studied, and the variations of unconfined compressive strength and deformation modulus with red clay mixing ratio and cement content were analyzed. Experimental results show that with the increase of red clay mixing ratio, the stress-strain curve of red clay modified phyllite soil exhibits typical elastoplastic characteristic when cement content is 0. When cement content is not 0, the stress-strain curve of composite improved phyllite soil approximates linear elastic characteristic, and the uniaxial compressive strengths and deformation moduli of red clay modified phyllite soil and composite improved phyllite soil increase. Under soaked condition, red clay modified phyllite soil disintegrates to result in a reduction of unconfined compressive strength and deformation modulus to 0. For composite improved phyllite soil, the unconfined compressive strength and deformation modulus decrease, with softening coefficients of 0.45-0.62 and 0.71-0.93 for cement contents of 3% and 5%, respectively, showing better water stability. When phyllite soil is improved by using cement and red clay, the increase in uniaxial compressive strength is better than the sum of the increments achieved by using cement and red clay alone, realizing an improvement effect of "1+1>2", that is, synergy. Therefore, it is advisable to adopt the composite improvement scheme to improve phyllite soil. Cement content of 3% and red clay mixing ratio of 20% can be used as an economic composite improvement scheme to meet the strength requirement of 350 kPa. In order to enhance water stability, rapid filling and full play of synergy, the composite improvement scheme of cement content of 5% and red clay mixing ratio of 40% can be considered.More>

2024, 24(3): 171-180. doi: 10.19818/j.cnki.1671-1637.2024.03.011

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Deformation characteristics of long-short pile composite foundation for high-speed railway in salt lake region

YANG Xiao-hua, WANG Dong-qing, ZHANG Sha-sha, KONG Xiang-xin, LI An-hong, ZHAO Yan-hu

Abstract: Based on the Tehran-Isfahan high-speed railway project in Iran, centrifuge model tests were conducted for full-length pile (concrete pile) composite foundation, full-short pile (gravel pile) composite foundation, and long-short pile (concrete pile-gravel pile) composite foundation, their settlement processes were simulated in embankment construction and following two years, and the effects of pile length ratio, pile spacing, short pile layout and filling height on the settlement characteristics were studied. Research results show that under the same geological condition, the post-construction settlements of the soils between piles for full-length, long-short, and full-short pile composite foundations are 28.16, 36.17, and 53.95 mm and reduce by over 70%, 60%, and 40%. Therefore, the post-construction settlements for full-length and long-short pile composite foundations meet the regulatory requirement of no more than 50 mm, and the post-construction settlement of long-short pile composite foundation is between the settlements of full-length and full-short pile composite foundations. For long-short pile composite foundation, increasing pile length ratio by 0.1 may reduce settlement by 7%-12% for the pile spacing of 3 times pile diameter and around 8% for the pile spacing of 4 times pile diameter, indicating that increasing pile length ratio can significantly improves settlement control, and the control is more effective as pile spacing increases. When the pile spacing increases from 3 times pile diameter to 5 times pile diameter, composite foundation settlement increases from 36.56 mm to 55.71 mm for a pile length ratio of 0.5, and from 28.38 mm to 45.93 mm for a pile length ratio of 0.7, indicating that settlement control is less effective at larger pile spacing. To meet the regulatory settlement requirement, the pile length ratio should not be less than 0.5 when the pile spacing is 5 times pile diameter. For a pile length ratio of 0.7, composite foundations settlements with one long-one short, one long-two short, and one long-three short pile arrangements are 28.37, 38.06, and 43.69 mm, indicating that placing more short piles between adjacent long piles can balance settlement control and economic efficiency. As the number of short piles increases, the stress on the long piles increases, but the stress distribution trend remains unchanged. Under different filling heights, in long-short pile composite foundation, gravel piles primarily move downward, long piles penetrate cushion layer, short piles penetrate soft soil, and localized potential slip surfaces form due to shear deformation and lateral extrusion of gravel piles.More>

2024, 24(3): 181-192. doi: 10.19818/j.cnki.1671-1637.2024.03.012

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Suppression effect of rail vibration absorber on self-excited vibration of wheel-rail friction

CUI Xiao-lu, ZHONG Yan-ming, XU Xiao-tian, TANG Chuan-ping, XU Jia, YANG Hong-juan, QI Wei

Abstract: Based on the frictional self-excited vibration theory and field investigation, the finite element model of the wheelset-rail-vibration absorber system in the small-radius curve section supported by DTVI2 fasteners and Cologne egg fasteners were established. The suppression effect of the two kinds of rail vibration absorbers on the rail corrugation was studied by two methods of complex eigenvalue analysis and instantaneous dynamic analysis. The effect laws of different parameters of rail vibration absorber on rail corrugation were analyzed by the least square method and particle swarm algorithm, and the optimal parameter combinations of rail vibration absorber under two kinds of fasteners were determined. Research results show that the main frequency of the frictional self-excited vibration of the wheelset-rail-vibration absorber system is 480 Hz before and after installing the rail vibration absorber. The maximum vertical vibration acceleration of the DTVI2 fastener decreases from 270.01 m·s^-2 to 206.07 m·s^-2, representing a decline of 23.71%. The peak value of power spectral density (PSD) reduces from 98.98 dB to 94.92 dB. The maximum vertical vibration acceleration of the Cologne-egg fastener decreases from 300.97 m·s^-2 to 211.44 m·s^-2, representing a decline of 29.74%. The peak value of PSD reduces from 101.58 dB to 95.14 dB. In the DTVI2 fastener section, the suppression effect on rail corrugation is the best when the mass of the rail vibration absorber is 14.0 kg, the connection stiffness is 9.0×10⁶ N·m^-1 and the connection damping is 1.0×10⁵ N·s·m^-1. In the Cologne-egg fastener section, the suppression effect on rail corrugation is the best when the mass of the rail vibration absorber is 7.5 kg, the connection stiffness is 1.07×10⁷ N·m^-1 and the connection damping is 1.0×10⁵ N·s·m^-1. It can be seen that the installation of rail vibration absorbers can effectively suppress the frictional self-excited vibration of the wheel-rail system, thereby suppressing the formation and development of rail corrugation. The suppression effect of the rail vibration absorber on rail corrugation in the Cologne-egg fastener section is better than that in the DTVI2 fastener section. Appropriate selection of the connection parameters of the rail vibration absorber can suppress the formation and development of rail corrugation.More>

2024, 24(3): 193-203. doi: 10.19818/j.cnki.1671-1637.2024.03.013

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Vertical vibration control of curved track structure based on inertial enhancement effect

YANG Zhou, FENG Qing-song, ZHANG Ling, LU Jian-fei

Abstract: In view of vertical vibration control of curved tracks, tuned mass damper inerter (TMDI) and amplitude magnification tuned mass damper (AM-TMD) were introduced based on inertial enhancement effect to realize better vibration control effects. Curved track was considered as a curved Timoshenko beam structure with discrete supports, and the energy functional variational method was used to establish a finite length curved track analysis model. Perfectly matched layer was introduced at both ends of curved track as a low reflection boundary condition for better simulating the infinite length track structure. The accuracy of analysis model and the effectiveness of perfectly matched layer were verified through the comparison with the dynamic response calculation results of existing infinite length discrete supported curved tracks. The effects of tuned mass damper (TMD), TMDI, and AM-TMD on the dynamic response of curved tracks under the action of fixed vertical harmonic load were systematically analyzed, and the vibration damping performances of TMD, TMDI, and AM-TMD were compared and evaluated. The relationship between the amplitude magnification factor and the operational capability of TMD was analyzed, and the working mechanism of AM-TMD was revealed. Research results show that the introduction of TMDI can efficiently make up for the quality defects of traditional TMD in implementing broadband control. Compared with TMD, the operating bandwidth of TMDI with the same parameters is broadened by about 1.5 times, and the maximum vibration attenuation rate increases by about 5.5 dB. The essence of AM-TMD lies in applying an amplitude magnification mechanism to synchronously enhance the effective mass, stiffness, and damping of TMD, thereby comprehensively improving the operational capability of TMD. Compared with TMD, the operating bandwidth of AM-TMD with the same parameters is expanded by about 2.0 times, and the maximum vibration attenuation rate increases by about 6.1 dB. Therefore, TMDI and AM-TMD are more effective than TMD from the perspectives of broadband control and high attenuation rate.More>

2024, 24(3): 204-216. doi: 10.19818/j.cnki.1671-1637.2024.03.014

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Comparison of dynamics characteristics of empty and full load gondola cars subjected to crosswind

WANG Kai-yun, HE Wen-tao, HU Yan-lin, GE Xin

Abstract: An aerodynamics model of freight train with one locomotive and four gondola cars was developed. The pressure distributions on the surfaces of empty and full load gondola cars at different wind speeds were studied. The aerodynamic loads on gondola cars were calculated and applied to the aerodynamics model. The dynamics characteristics of empty and full load gondola cars under crosswinds with different speeds were analyzed from the perspectives of vehicle posture and operation safety. Research results show that the first gondola car behind the locomotive suffers the largest side force, lift force and rolling moment under crosswind. At a wind speed of 10 m·s^-1, the maximum values are -7.17 kN, 4.59 kN, and 1.89 kN·m, respectively. For the first gondola car, when wind speed is 10 m·s^-1, the side force, pitch moment, and yaw moment at full load state decrease by 15.8%, 79.0%, and 12.2% compared to no load state, respectively. Conversely, the lift force and side rolling moment increase by 39.9% and 56.6%, respectively. Thus, the loading state significantly affects the aerodynamic loads on gondola cars under crosswind. Empty gondola car is more susceptible to the aerodynamic loads. At the wind speeds of 25 and 30 m·s^-1, the lateral displacements of the first empty gondola car are -12.66 and -14.82 mm, respectively, while those of the first full load gondola car are -12.01 and -13.68 mm, respectively. The side rolling angles of the first empty gondola car are -0.69° and -0.83°, respectively, compared to -0.64° and -0.73° for the first full load gondola car. Therefore, the lateral displacement and side rolling angle of empty gondola car are greater than those of full load gondola car. At a wind speed of 25 m·s^-1, the wheel load reduction rate of empty gondola car reaches 0.68, exceeding the limit of 0.65, while that of full load gondola car is 0.24, below the limit. At a wind speed of 30 m·s^-1, the overturning coefficient of empty gondola car reaches 0.75, approaching the limit of 0.80, while that of full load gondola car is only 0.23. Thus, there is a safety risk for empty gondola cars under high-speed crosswind.More>

2024, 24(3): 217-226. doi: 10.19818/j.cnki.1671-1637.2024.03.015

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Impact of key airtight components on pressure comfort in metro train

LI Yang, LIU You-mei

Abstract: To comprehensively analyze the impact of external pressure on passenger ear comfort during metro train operation, a real vehicle line test method was employed to measure the internal and external pressures of key airtight components (pressure wave protection valve for air conditioning, door pneumatic auxiliary lock, and gangway drainage hole screen) under different sealing conditions when the metro train passed through the tunnel at a constant speed. The fluctuating characteristics of external pressure, the pressure distribution law of the train in the longitudinal direction, as well as the influences of key airtight components on the pressure change amplitude inside the train were analyzed. Research results show that external pressures on the head vehicle and the middle vehicle are greatly affected by the compression wave generated while the train head enters the tunnel. The peak pressure on the train body surface gradually decreases from the head vehicle to the tail vehicle. When the air conditioning is on, compared with the situation when the pressure wave protection valve is enabled, the pressure change amplitude inside the train increases by 48%-61% within 3 s and 75%-90% within 1 s when the pressure wave protection valve is not enabled. This indicates that the pressure wave protection valve for air conditioning has a significant effect on the pressure comfort inside the train. When the air conditioning is off, compared with the situation when the door pneumatic auxiliary lock is enabled, the pressure change amplitude inside the train increases by 39%-46% within 3 s and by 69%-78% within 1 s when the door pneumatic auxiliary lock is not enabled. This indicates that the importance of the door pneumatic auxiliary lock's effect on the pressure comfort inside the train is second to the pressure wave protection valve for air conditioning. When the air conditioning is off, compared with the situation when the gangway drainage hole screen is enabled, the pressure change amplitude inside the train increases by 3%-11% within 3 s and 1%-13% within 1 s when the gangway drainage hole screen is not enabled. This indicates that the gangway drainage hole screen has a relatively small effect on the pressure inside the train.More>

2024, 24(3): 227-237. doi: 10.19818/j.cnki.1671-1637.2024.03.016

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Anti-lock braking control based on interval type-2 fuzzy logic

WANG Jun-cheng, LYU Lin-feng, WANG Fa-hui

Abstract: To cope with the problem of weak anti-interference ability and poor slip ratio control effect when the traditional fuzzy logic anti-lock braking control facing different road surface adhesion coefficients and different ideal slip ratios, an interval type-2 fuzzy logic anti-lock braking control system and method were proposed. The slip ratio error was taken as input of the control system. The interval type-2 fuzzy sets were utilized to describe the slip ratio error and its change rate. Then the ideal braking torque output was obtained after the fuzzification, fuzzy inference, fuzzy type-reduction, and defuzzification. The fuzzy rule activation degree interval was calculated on the premise of fuzzy variables membership degree determined by the upper and lower membership functions. Through this process, the system's anti-interference ability was enhanced, and the accurate slip ratio tracking was ensured. Using the MATLAB/SIMULINK software, the vehicles equipped with the proposed controller and traditional controller were simulated for the anti-lock braking control performance under different road surface adhesion conditions, and the anti-lock hardware-in-the-loop platform was conducted for verification analysis. Research results show that under the interval type-2 fuzzy logic anti-lock braking control, the error mean squares of slip ratios for front and rear wheels of vehicles on the low adhesion coefficient road surface decrease by 52.96% and 57.36%, respectively, the braking distance reduces by 0.24 m, and the braking time declines by 0.04 s. On the middle adhesion coefficient road surface, the error mean squares of slip ratios decrease by 65.15% and 73.32%, respectively, the braking distance reduces by 0.36 m, and the braking time declines by 0.05 s. On the high adhesion coefficient road surface, the error mean squares of slip ratios decrease by 47.20% and 39.57%, respectively, the braking distance reduces by 0.19 m and the braking time declines by 0.02 s. It can be seen that compared with the traditional fuzzy logic anti-lock braking control, the proposed interval type-2 fuzzy logic anti-lock braking control achieves better slip ratio control effects under different braking conditions.More>

2024, 24(3): 238-250. doi: 10.19818/j.cnki.1671-1637.2024.03.017

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Pro-active real-time scheduling approach of apron vehicles based on mixed strategy

BAO Dan-wen, CHEN Zhuo, YAO Xin-yu, ZHOU Jia-yi

Abstract: To address the scheduling perturbation problem of apron vehicles caused by uncertain events, a pro-active real-time scheduling approach of apron vehicles based on a mixed strategy was proposed. A flexible operation mechanism considering apron partitioning was designed to allow vehicles to adaptively adjust their parking areas. A mixed-integer programming model was established to minimize the total response time of flight support requests and the total travel distance of apron vehicles. The service cost was considered from both the temporal and spatial dimensions, and the spatio-temporal service radius indicator of vehicles was introduced. A flexible waiting strategy and a dynamic relocation strategy based on the future request information were designed. The quality of flight support service was enhanced by these pro-active scheduling strategies, and the operational cost of service vehicles was reduced. An empirical study was conducted at Beijing Capital International Airport. Research results show that compared to traditional scheduling modes, the flexible operation mechanism can effectively improve the vehicle operation efficiency and reduce the turnaround distance of idle vehicles. The total request response time and total vehicle travel distance decrease by 37.0% and 36.8%, respectively. The flexible waiting strategy is suitable for peak periods with dense flight landings and takeoffs. The total vehicle travel distance reduces by 11.6%. The dynamic relocation strategy is applicable to apron areas with broad coverage. The total request response time reduces by 17.8%, while generating higher relocation costs and increasing the total vehicle travel distance by 12.5%. Therefore, for busy large hub airports, adopting a mixed strategy can effectively balance the quality of flight support service and the operational cost of service vehicles.More>

2024, 24(3): 251-265. doi: 10.19818/j.cnki.1671-1637.2024.03.018

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Long voyage planning and battery charging/swapping strategy of pure electric green ships

LIANG Min-cang, WANG Sheng-zheng

Abstract: To solve the problems of long voyage planning and dynamic planning of site selection of battery charging/swapping stations for pure electric ships, a feasible multi-variable and multi-objective optimization method was proposed to realize the synchronous optimization of speed and battery charging/swapping strategy. A double objective function of the lowest energy consumption and the shortest voyage time was established, the environmental and operational factors affecting long voyage planning for pure electric ships were analyzed, and the constraints of speed, voyage time and energy consumption were established. The operations management mode of the containerized battery was studied, and two optimization models of energy supply charging according to actual power consumption charging and one-time battery swapping charging were built. The models were solved by a non-dominated sorting genetic algorithm and verified by experiment cases. Research results show that based on case data conditions, before optimization, the maximum average speed of 8.5 kn ensuring continuous sailing to the second battery charging/swapping station for recharging requires 96 637.7 kWh of energy consumption and 62.1 h of total sailing time. When charging for actual power consumption, the battery charging/swapping strategy obtained by the optimization models requires recharging at the second battery charging/swapping station. When the optimization goal is the shortest sailing time, the total sailing time is only 56.9 h. When the optimization goal is the minimum energy consumption, the total energy consumption is only 65 762.5 kWh. In the case of one-time battery swapping charging, there are two strategies in the optimization model, including no battery swapping in the whole voyage and one-time battery swapping at the second battery charging/swapping station. The accumulated energy consumption before battery swapping is close to the total capacity of the battery on the ship, which can maximize the energy utilization. The optimization model can provide optimal speed and battery charging/swapping strategy under different battery operations management modes and user preferences, and can be applied to determine site selection of battery charging/swapping stations, which is of great significance to improve the operating efficiency of pure electric green ships.More>

2024, 24(3): 266-278. doi: 10.19818/j.cnki.1671-1637.2024.03.019

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Modeling and prediction method of ship maneuvering motion facing environmental uncertainty

CHEN Li-jia, ZHOU Xin-wei, YANG Pei-yi, WANG Kai, LI Sheng-wei

Abstract: In response to the issue of prediction accuracy of ship maneuvering motion under complicated environmental factors, a grey box identification modeling and prediction method for ship maneuvering motion under environmental uncertainty was proposed. The separated ship maneuvering motion model structure was referenced, the ship maneuvering motion mechanism was considered, and a simplified grey box model was developed. Suitable test subjects were selected, and parameter identification was conducted on the established ship maneuvering motion grey box model using the least squares support vector machine algorithm. The generalization ability was examined by means of the turning cycle tests and zigzag maneuvering tests. By analyzing the environmental uncertainty factors, the wave force interference model, data transmission delay model, and sensing device error model were constructed. Based on these models, the ship motion response training data affected by multiple environmental uncertainties were generated. Through the simulated tests, the prediction accuracy of the proposed method under environmental uncertainties was validated. Research results reveal that in ship maneuvering motion prediction tests with environmental uncertainty factors, when the sensing device error gradually increases from 0 to 5% and 10%, except for the rolling speed affected by a small initial magnitude, the root mean square errors (RMSEs) of other ship motion response prediction results increase by less than 10%, so the accuracy of the prediction model can be effectively guaranteed. Under the extreme condition with a 20% sensing device error, the prediction errors of surge speed, sway speed, and yawing speed increase by 4.65%, 15.97%, and 18.17%, respectively compared to the 0 error level, so the error increase is effectively controlled below 20%. Thus, the ship maneuvering motion modeling and prediction method can achieve a high-precision prediction of ship maneuvering motion under the interference of environmental uncertainty factors to a certain extent.More>

2024, 24(3): 279-295. doi: 10.19818/j.cnki.1671-1637.2024.03.020

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Trajectory prediction method for high-speed train group tracking operation based on LSTM-KF model

ZHANG Miao, HE Yi-juan, YANG Bo-yu, LUO Zheng-wei, LU Wan-li, TANG Tao, LI Kai-cheng, LYU Ji-dong

Abstract: The problem of operation trajectory prediction in high-speed train group tracking was studied to further shorten train tracking distance and improve transportation capacity. The advantages of the long short-term memory (LSTM) model in processing sequence data and the ability of the Kalman filter (KF) model to process noise were considered, and a new LSTM-KF model for train trajectory prediction was proposed. The historical data of train operation were used for LSTM model training, and train trajectory prediction curve was generated. The predicted results and dynamics mechanism were integrated by the KF model to correct the calculation results, smoothing the train trajectory predicted by the LSTM model. The experiment was simulated and verified based on the standard data of lines on the simulation and test platform of the high-speed railway train control system. Simulation results show that the prediction errors of the position relative to the true value of the three models of LSTM-KF, LSTM, and recurrent neural networks (RNN) are 78, 798, and 911 m, respectively after 30 predicted steps under the cruise driving condition. The prediction errors of the speed are 1, 22, and 1 m·s^-1, respectively. The position root mean square error (RMSE) of the LSTM-KF is 7% and 15% of that of LSTM and RNN, and the speed RMSE of the LSTM-KF model is 14% and 30% of that of LSTM and RNN. The mean position prediction errors under acceleration condition are 94, 294, and 2 691 m, respectively, and the mean speed prediction errors are 0.09, 10.05, and 2.74 m·s^-1, respectively. The mean position prediction errors under deceleration condition are 1 181, 4 135, and 4 079 m, respectively, and the mean speed prediction errors are 1.14, 6.01, and 13.52 m·s^-1, respectively. It can be seen that the prediction accuracy under different operating conditions can be significantly improved in the LSTM-KF model, and long-term data sequences can be effectively generated to provide decision-making for the tracking operations of high-speed train groups.More>

2024, 24(3): 296-310. doi: 10.19818/j.cnki.1671-1637.2024.03.021

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2024 Vol. 24, No. 3

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