• ISSN 0258-2724
  • CN 51-1277/U
  • EI Compendex
  • Scopus
  • Indexed by Core Journals of China, Chinese S&T Journal Citation Reports
  • Chinese S&T Journal Citation Reports
  • Chinese Science Citation Database

2020 Vol. 55, No. 3

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Structural Nonlinear Damage Identification Based on Autoregressive Conditional Heteroskedasticity Conversion Index
GUO Huiyong, WANG Zhihua, LI Zhengliang
2020, 55(3): 459-466, 517. doi: 10.3969/j.issn.0258-2724.20180316
[Abstract](552) [FullText HTML] (318) PDF 1129KB(11)
Abstract:
To solve the identification problem of time-domain nonlinear damage, the incorporation of an autoregressive conditional heteroskedasticity (ARCH) model with damage detection was proposed. First, the basic theory of ARCH model was described, and the order estimation and maximum likelihood parameter estimation of ARCH model were proposed. Then, the characteristics of nonlinear damage were analyzed, and a damage detection theory based on ARCH model was presented. Finally, it is difficult for the damage index based on degree of freedom to identify damage locations, an autoregressive conditional heteroskedasticity conversion index (ARCHCI) was proposed. A three-storey frame experiment was used to verify the effectiveness of the ARCHCI, the effect of measurement error and model error was also considered in the experiment. The results show that the ARCHCI value of the damaged third storey is at least 21.7% higher than that of the cepstrum metric conversion index when the nonlinear gap distances are 0.05 mm and 0.10 mm; the ARCHCI value of the third storey is 3.7% higher than that of the cepstrum metric conversion index when the gap distance is 0.20 mm.
Multi-level Semantic Retrieval Method for Landslide Disaster Data
ZHU Qing, LI Maosu, DING Yulin, FENG Bin, ZHANG Junxiao, CAO Zhenyu, QIU Linyao, YIN Hao
2020, 55(3): 467-475. doi: 10.3969/j.issn.0258-2724.20180695
[Abstract](645) [FullText HTML] (339) PDF 907KB(24)
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How to quickly and accurately find the superior information to meet the needs of disaster assessment tasks in massive spatio-temporal big data of landslide hazards is the key basis for comprehensive disaster reduction and disaster relief. The traditional disaster data retrieval is mainly based on the passive retrieval method of “artificial experience + keywords”, which makes it difficult to balance the accuracy and timeliness of tasks. This paper proposes a multi-level semantic retrieval method of spatio-temporal data for disaster assessment tasks. By establishing an explicit semantic description of data feature requirements and high-level semantic mapping between task requirements and data features, a multi-level semantic matching data retrieval algorithm is designed to realize superior data aggregation for disaster assessment tasks. Application of the proposed method to the landslide hazard assessment of Maoxian County in Sichuan demonstrates its high query efficiency such as a seconds-level retrieval efficiency in dealing with disaster data in a 900 km2 and 90 day range. The accuracy of the recommended dominant data set is also significant, and the average closeness of the recommended results under the 60-day time gap threshold is over 90%. The results show that the method can quickly and automatically acquire disaster data according to the mission requirements, thus significantly improving the disaster mitigation emergency response capability.
Homogeneous Generalized Yield Function for Frame Members with Box Section
YANG Lufeng, SONG Shasha, XIE Weiwei, ZHANG Wei
2020, 55(3): 476-484. doi: 10.3969/j.issn.0258-2724.20180754
[Abstract](629) [FullText HTML] (319) PDF 1916KB(18)
Abstract:
In order to overcome limitations of the traditional generalized yield function (GYF), a homogeneous generalized yield function (HGYF) is proposed for box sections, which is insensitive to sectional geometry of box sections and applicable for plane and spatial frame structures; and a linear-elastic iterative method with higher efficiency is presented for ultimate bearing capacity of framed structures. Firstly, different generalized yield functions (GYF) are investigated and the suitable one is selected as insensitive to the geometric parameters of box sections. Then a set of fitting points are determined according to the comprehensive test method, based on which an HGYF was developed by regression analysis with a wide range of application for box sections. Finally, a linear-elastic iterative method is presented with high efficiency for the ultimate bearing capacity of frames with box section on the basis of elastic modulus reduction method (EMRM). Numerical examples show that the proposed HGYF achieves satisfying stable results with a wide range of application for plane and spatial frames, overcoming not only the instability of the traditional GYF, but also the sensitivity of the existing HGYF to geometry of sections which is unsuitable for spatial frames. The relative error of the established method is less than 3% compared with the traditional elasto-plastic incremental analysis method, and the calculation time is less than 10% that of the traditional analysis method, which shows the accuracy and efficiency of this method.
Discontinuous Deformation Analysis Method for Deformation Response of Hidden Resources in Collapse Area under Blasting Excavation
XU Hai, LUO Zhouquan, WEN Lei, QIN Yaguang
2020, 55(3): 485-494. doi: 10.3969/j.issn.0258-2724.20190033
[Abstract](706) [FullText HTML] (355) PDF 2894KB(13)
Abstract:
Aiming at the safety problem of hidden resources mining in collapse area of underground metal mines, the discontinuous deformation analysis (DDA) is used to address the deformation response of hidden resources in collapse area under blasting dynamic load. The calculation process of DDA method is stated using the minimization principle of potential energy and plane strain assumption. Meanwhile, free field boundary is inserted in the DDA model and the tangential free damper and normal free damper of boundary units are used to discuss the deformation response of blasting excavation after grouting reinforcement near the collapse area. Results show that the input wave in the DDA model is characterized by obvious hysteresis, and the wave propagation velocity computed considering the hysteresis is consistent with the measured results. Modelling results after excavation indicate that the deformation under the slip line of collapsed zone is clearly less than that above the slip line, which is consistent with the actual monitoring results after excavation. Moreover, the velocity amplification coefficient of monitoring points in the collapsed zone increases with increasing distance from blasting source. Therefore, it is reliable to introduce free-field boundaries and the free dampers of boundary units into the DDA model to study the deformation response of stopes at the edge of collapse area under blasting dynamic load.
Random Walking Crowd Model Considering Pedestrian Synchronization Rate
CAO Lilin, CAO Dong, YU Guojun, LI Aiqun
2020, 55(3): 495-501. doi: 10.3969/j.issn.0258-2724.20180656
[Abstract](643) [FullText HTML] (295) PDF 1775KB(20)
Abstract:
In order to study the influence of walking crowd synergy on the human-induced vibration of structures, the vertical vibration of a footbridge under the action of walking crowd was analyzed using the random walking crowd model considering pedestrian synchronization rate. Firstly, a random walking crowd centralized model and discrete model considering pedestrian synchronization rate were proposed by random analysis of the walking crowd. Secondly, a method for vertical vibration response analysis of structure subjected to random walking crowd was established by considering the vertical coupling effect between human and structure under the two models. Finally, change rules of vertical acceleration responses and dynamic characteristic parameters of the footbridge under the two different random walking crowd models were compared and analyzed. Results show that the 1-s root-mean-square (RMS) acceleration responses of the footbridge under the two pedestrian walking models both increase first and then decrease with the crowd density increasing. Beyond the crowd density of 0.2 person/m2, the 1-s RMS acceleration of the footbridge in the random walking crowd discrete model is greater than that in the centralized model, and increasing the pedestrian spacing in the synchronization zone of the centralized model is beneficial to reducing structural vibration responses. As crowd density increases, the instantaneous frequency of footbridge decreases constantly; the instantaneous damping ratio of the footbridge increases first and then decreases, with a maximum 6-fold and 7-fold increase under the centralized model and the discrete model, respectively. In short, the random walking crowd model considering pedestrian synchronization rate can accurately reflect the actual crowd walking load of footbridges and therefore provide reference for the analysis and evaluation of human-induced vibration responses of footbridges.
Thermo-Elastic Vibration Analysis of Functionally Graded Material Pipes in Elastic Matrix
TONG Guojun, LIU Yongshou, WANG Yingchao
2020, 55(3): 502-508. doi: 10.3969/j.issn.0258-2724.20180287
[Abstract](598) [FullText HTML] (287) PDF 1266KB(9)
Abstract:
In order to investigate the fluid-structure coupled vibration problems of functionally graded material (FGM) fluid conveying pipes embedded in elastic matrix. Firstly, the vibration control equation of the FGM pipe was derived according to Euler-beam model theory. Then, the differential quadrature method was used to solve the vibration control equation. Finally, the influence of the volume fraction of the material component, temperature, slenderness ratio and elastic coefficient of elastic matrix on natural frequency and critical velocity of the system was discussed according to the calculated results.The following conclusions are obtained: (1) The increase of the volume fraction of the internal material components will lead to the dimensionless natural frequency of the system increase and the critical velocity decrease (exponential n increases from 0 to 10, the natural frequency increases by about 13% and the critical velocity decreases by about 6% when the flow velocity is 0). (2) With the increase of temperature, the natural frequency and the critical velocity of the system will decrease (when the length-diameter ratio is 100, the temperature increases by 30 K, the natural frequency decreases by about 4% wand the critical velocity decreases by about 14% hen the flow rate is 0). The natural frequency of the system decrease obviously when the slenderness ratio decreases (when the length-diameter ratio is 100, 50 and 20, the natural frequencies of the system are 160, 41.1 and 11.87, respectively). (3) The natural frequency of the system decreases with the increase of the external radius, the thinner the tube wall the faster it changes, the thicker the tube wall the slower it changes (the decrease of natural frequency caused by the increase of outer diameter from 0.1 m to 0.11 m is about 100 times that from 0.19 m to 0.2 m). (4) The increase of the elastic coefficient k will improve the natural frequency of the system (the natural frequency of the system increased by about 74% when k increases by three times).
Characteristics Analysis of Soil Arching Effect Behind Pile Based on Transparent Soil Technology
CHEN Qiang, DONG Guicheng, WANG Chao, ZHU Baolong, ZHAO Xiaoyan
2020, 55(3): 509-517. doi: 10.3969/j.issn.0258-2724.20190744
[Abstract](664) [FullText HTML] (357) PDF 1528KB(29)
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In order to study the characteristics and evolution process of soil arching effect behind a circular pile, an experimental study on pile-soil interaction based on the transparent soil technology was carried out from a microscopic perspective. Firstly, the tests as to transparent soil ratio were carried out to obtain the soil with desirable physical and mechanical properties. Secondly, the experimental system was designed and the speckle field image of the interaction between the transparent soil and pile was obtained. Finally, the displacement vector diagram was obtained through particle image velocimetry (PIV) technique, and the displacement variation rule of the transparent soil was further analyzed. The results show that the movement trend and displacement characteristics of soil particles under the action of the circular pile can be obtained through displacement vector, and the arch structure formed by displacement contour, namely, the soil arch structure behind the pile, can be further interpreted, as it presents a parabolic shape and its range is related to pile diameter, pile spacing and depth. The larger the pile diameter is, the larger the soil arch area is. When the pile diameter is 30 mm, the soil arch is up to 100 mm. Meanwhile, the pile-soil interaction affects larger region. The larger the pile spacing is, the larger the maximum arch height is. When the pile spacing is 80 mm, the soil arch height also reaches 100 mm. The soil arch height under different depths shows a similar trend. The deeper the depth is, the smaller the maximum arch height is. When the depth is 50 mm, the arch height is 60 mm. According to the fitting formula, the maximum arch height decreases gradually from the pile top to the bottom along the pile, and at the same time, it increases at first and then tends to stabilize with the increase of soil displacement. The stable value is correlated positively with pile diameter and pile spacing and negatively with depth.
Crack Detection of 3D Asphalt Pavement Based on Multi-feature Test
QIU Yanjun, WANG Guolong, YANG Enhui, YU Xiaoli, WANG Chenping
2020, 55(3): 518-524. doi: 10.3969/j.issn.0258-2724.20180270
[Abstract](772) [FullText HTML] (330) PDF 1201KB(41)
Abstract:
In order to solve the accuracy problems in the crack detection of 3D asphalt pavement, which are mainly caused by low contrast between cracks and the surrounding area and complex pavement textures, a three-step preprocessing was conducted on original 3D images firstly, including size reducing, intensity correction and Gaussian smoothing. Then, three predominant feature tests of tilt-level, Gaussian-distribution and edge-gradient were applied to the image profiles of four directions successively so as to obtain the crack profiles. Moreover, the crack profiles of four directions were merged and denoised to acquire the intact cracks. Finally, according to the roughness of pavement surface, a related parameter in the Gaussian-distribution test was adjusted to realize the crack detection of high accuracy. The experiment result indicates that the proposed algorithm can reach 89.19% of accuracy, 93.69% of recall and 91.06% of F-measure, which outperforms another two typical 3D recognition algorithms based on the theories of 3D shadowing and crack seeds.
Performance and Application of Adjustable Height Support
WANG Yang, WANG Liangkun, SHI Weixing, LIU Chengqing
2020, 55(3): 525-530. doi: 10.3969/j.issn.0258-2724.20180391
[Abstract](941) [FullText HTML] (347) PDF 741KB(38)
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To overcome the defaults of difficult to adjust the height in existing steel supports, an adjustable height support was proposed, whose height could be adjusted in a range, to adapt to the complexity and variability of the site construction conditions, ensure the precision bearing, and improve the work efficiency. The bearing system could be divided into two parts: coarse and fine parts. Before adjusting the height, the jack should be set between the support and the support structure, and then adjusted the position of the cheese block by adjusting the knob. The application of the adjustable height support in a real project was proposed, the support arrangement locations, construction processes and the displacement, stress and strain health monitoring system were all discussed in detail, and the support resultant force was taken as the basis of the support elevation in different construction stages. The results show that the support can monitor the reaction force and adjust the height of the support in real time. For example, the maximum pressure difference of southeast abutment decreases from 2 266.8 kN before adjustment to 39.4 kN after adjustment. The bearing force value of abutments is similar, and the stress on piers and foundations tends to be uniform. It is beneficial to ensure the safety and durability of piers and foundations.
Analytical Method for Calculation of Surrounding Rock Pressure of Shallow-Buried and Unsymmetrically Loaded Tunnel Adjacent to Variable Slope
YAN Tao, LI Kunjie, MOU Zhiheng, ZHANG Jiaxin, YU Li, LI Qi, LI Guoqing, PENG Tao
2020, 55(3): 531-536. doi: 10.3969/j.issn.0258-2724.20180825
[Abstract](1037) [FullText HTML] (455) PDF 893KB(29)
Abstract:
At present the surrounding rock pressure of shallow-buried and unsymmetrical loading tunnels is generally calculated by code for design of road tunnel. However, when the two portal parts of twin tunnels are not located at the same mileage, one of them will be constructed adjacent to the excavated subgrade slope, rather than under a natural mountain slope. In this case, the code is not applicable to the calculation of surrounding rock pressure of the tunnel. To solve this problem, an analytical solution for calculating the surrounding rock pressure of the shallow-buried and unsymmetrically loaded tunnel adjacent to variable slope is proposed using the limited equilibrium theory, taking a highway tunnel in Anhui province as a prototype. The results indicate that due to the variable slope, the vertical pressure in the surrounding rock of deep-buried side calculated by the modified algorithm is smaller than that calculated by the code with a relative error of 15.98%, while values of horizontal pressure in the deep-buried rock remain unchanged. However, in the surrounding rock of shallow-buried side, both vertical and horizontal rock pressures calculated by the modified algorithm are smaller than that by the code, with relative errors being 24.93% and 5.50% for vertical and horizontal pressures, respectively. Therefore, the variable slope has a greater influence on the shallow side. In addition, the surrounding rock with variable slope has a larger bias rate than that with a natural slope. Values of stress, equivalent stress and rock displacement of the former are approximately 1–5 times larger than those of the latter, indicating that the tunnel with variable slope is more unsafe.
Numerical Simulation of Wave-Current Forces Acting on Cofferdam for Sea-Crossing Bridge Based on Large Eddy Simulation
KANG Azhen, YIN Ruitao, ZHU Bing, LI Xin, ZHANG Jiawei
2020, 55(3): 537-544, 587. doi: 10.3969/j.issn.0258-2724.20180222
[Abstract](635) [FullText HTML] (326) PDF 1349KB(11)
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The foundation construction of a sea-crossing bridge may encounter complex sea conditions, such as deep-water, large-wave and rapid-flow conditions. Wave-current forces may even become dominant loads for the cofferdam construction of a sea-crossing bridge. To study wave-current forces acting on cofferdams of sea-crossing bridges, a numerical model for simulation of three-dimensional (3D) wave-current interactions with a structure was established using the large eddy simulation method. In this model, the vertical multiple-layer σ-coordinate transformation model was used to track the 3D wave current-induced free surface, and the immersed boundary method (IBM) was added to deal with the irregular structural surface. The proposed 3D numerical model was then validated and applied to simulate oblique wave-current interaction with a rectangular bridge cofferdam under different length-width ratios. The results indicated that the established 3D numerical model could well simulate wave-current forces acting on the rectangular structure. When the length-width ratio equals 1.0, the incident angle has little effect on the total wave-current forces due to structural symmetry, with a growth below 5%. As the length-width ratio increases, however, the incident angle will have greater impact on the total wave-current forces acting on the rectangular cofferdam. At a length-width ratio of 2.0, the total force acting on the structure when wave current is incident along longitudinal direction (90°) are 2.48 times as big as that when it is incident along transverse direction (0°). Wave-current forces acting on rectangular structure are generally bigger than wave forces in the wave only condition; however, influence coefficients of incident angles on wave-current forces or wave forces are relatively close.
Electromagnetic-Thermal Field Coupling Calculation of Contactless Power Transfer Vehicle
WANG Yanqin, ZHANG Qiumin, LIN Feihong, DONG Liang
2020, 55(3): 545-551. doi: 10.3969/j.issn.0258-2724.20191123
[Abstract](525) [FullText HTML] (273) PDF 1324KB(18)
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The application of contactless power transfer technology in urban rail transit has attracted more and more attention. However, there are still many problems to be addressed in the practical application of high-power contactless network power supply technology, among which the eddy current heating problem caused by electromagnetic induction is one of major concerns. In this work, an electromagnetic induction heating model of contactless power transfer vehicle is established according to the electromagnetic induction principle and the heat transfer theory. Using the finite element method, the thermal field distribution of the contactless power transfer vehicle is calculated, and numerical simulations of vehicle heating under different load conditions are performed. In addition, the heat dissipation performance of the receiving coils with radiator and air cooling is compared. Results show that the temperatures of both the receiving coils and bogie rise significantly. As the current of the transmitting coils increases and the distance of the air gap decreases, the temperature of each part of the vehicle has an upward trend. The maximum temperature of the receiving coils with the radiator is 126 ℃ lower than that without the radiator, and the performance of the radiator can be further improved by changing its heat transfer coefficient. Meanwhile, the temperature of the receiving coils with air cooling is reduced by 131.2 ℃. Compared with the radiator, the air-cooling heat dissipation performance is slightly better, and the air-cooling effect is more prominent as the wind speed increases.
Discharge Development and Characteristics of Oil-immersed Pressboard Surface with Different Moisture Contents
WU Guangning, ZHOU Peng, GAO Bo, YU Rui, HU Guangcai
2020, 55(3): 552-560. doi: 10.3969/j.issn.0258-2724.20190210
[Abstract](609) [FullText HTML] (253) PDF 1733KB(16)
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The increase of moisture content in power transformer will seriously affect the insulation performance of oil-paper, more easily resulting in the surface discharge fault of insulated pressboard. In order to study the discharge characteristics of insulated pressboard with different moisture contents under AC condition, a typical model of needle board surface discharge was established. Based on the pulse current method, the characteristic charts of the surface discharge model were measured in real time, and a high-speed camera was used to record the formation and development of white mark on insulated pressboard. The variation trend of initial discharge voltage and flashover voltage under different moisture contents of pressboard was analyzed, and then that of the related discharge characteristic parameters was analyzed. The results show that the increase of moisture content in pressboard significantly reduces the onset voltage. The process of surface discharge and white mark formation and development on pressboard with different moisture contents can be divided into four stages. There is a one-to-one relationship between the four stages of surface discharge and white mark formation and development. By observing and analyzing the microstructure of insulated pressboard, it is found that the fibers of the pressboard were severely broken after tests. The higher the moisture content of the pressboard before tests, the more serious the damage to the surface of the pressboard. When the moisture content of pressboard increases from less than 0.5% to 3.8%, the initial discharge voltage decreases by 61.3%.
Axial Bearing Capacity of Angle Parallel Reinforcement for High Voltage Transmission Towers
YAO Yao, WANG Lingxu, ZHANG Youjia
2020, 55(3): 561-569. doi: 10.3969/j.issn.0258-2724.20190370
[Abstract](580) [FullText HTML] (284) PDF 1206KB(15)
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The risk of transmission tower collapse can be effectively controlled by improving the bearing capacity of its local stability. Through the test of six-angle parallel reinforcement under axial compression, a single-angle axial compression test and the analysis of 13 finite element models, the load-displacement curves of the specimens, the load-strain curves and Mises stress nephogram are obtained. Further the laws of stress and strain of the specimens and how design parameters affect the component bearing capacity are explored. The results show that the local buckling instability is the main failure mode of the specimens. The maximum strength of the reinforced angle unit reaches 223.1 MPa, and the maximum strength of the board clamp element reaches 83.7 MPa. The overall strain of the specimen is mainly vertical strain, and that of the board clamp is mainly shear strain. The buckling formula of uniform plate theory can calculate the ultimate bearing capacity of the reinforced specimen. The parallel reinforcement can improve the bearing capacity of single angle by 40%.
Hierarchical Fault Location Method for Distribution Network with Special Load
GAO Fengyang, LI Zhaojun, YUAN Cheng, LI Xiaofeng, QI Xiaodong
2020, 55(3): 570-578. doi: 10.3969/j.issn.0258-2724.20190414
[Abstract](535) [FullText HTML] (240) PDF 783KB(11)
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Special load is connected to the distribution network, which enhances the interaction between the power supply, load and power grid, and imposes higher requirements for fault location. To deal with this, a hierarchical location method for fast locating fault points is proposed. Firstly, the incompleteness of the genetic algorithm based fault location model is analyzed for single-layer distribution network with special load. Secondly, based on the theory of the single-layer model, a regional positioning method and a segment method are proposed, which respectively improves quantum immune algorithm and implicit enumeration method. Finally, a comparative simulation is carried out between the proposed model and the single-layer model that is based on a single intelligent algorithm. Compared with the genetic algorithm, immune algorithm and improved single-layer positioning model constructed by quantum immune algorithm, the hierarchical positioning method can greatly simplify the complexity of the fault identification model, ensure the fault tolerance and stability of the positioning while improving the positioning efficiency. In addition, this method reduces the fault search dimension by 69%, takes less than 1s to locate the fault, and the fault identification rate is 100%.
Application of Hierarchical Extreme Learning Machine in Prediction of Insulator Pollution Degree Using Hyperspectral Images
YANG Gang, LI Hengchao, TAN Bei, SHI Chaoqun, ZHANG Xueqin, GUO Yujun, WU Guangning
2020, 55(3): 579-587. doi: 10.3969/j.issn.0258-2724.20190093
[Abstract](612) [FullText HTML] (268) PDF 1031KB(15)
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Hyperspectral images possess merging properties of image and spectrum, wide spectral range, and high spectral resolution, which can finely reflect the material microscopic characteristics. To this end, hyperspectral imaging technology is introduced to research the insulator pollution degree in a non-contact way. Considering that extreme learning machine (ELM) has high learning efficiency and strong generalization ability, we construct a ELM with regularization constraint based insulator pollution degree prediction (ELM-IPDP) model. Besides, in order to further improve the prediction performance, hierarchical ELM (HELM) is utilized to learn the effective, abstract, and discriminative feature representations from the complex hyperspectral images, and the HELM based insulator pollution degree prediction (HELM-IPDP) model is proposed. Experiments are performed with different amounts of training data and numbers of neurons in hidden layers. Experimental results show that the prediction performance is basically improved with the increase of numbers of neurons in hidden layer and training samples. Specifically, when the proportion of training sample and test sample is 9∶1, root mean squared error (RMSE) and correlation coefficient of the ELM-IPDP model are 0.040 3 and 0.944 7, while those of the HELM-IPDP model are up to 0.022 3 and 0.972 0, respectively.
Extended Unifying Principle of Clause Elimination in First-Order Logic
NING Xinran, XU Yang, HE Xingxing
2020, 55(3): 588-595. doi: 10.3969/j.issn.0258-2724.20180974
[Abstract](542) [FullText HTML] (233) PDF 749KB(12)
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Simplifications are indispensable steps of first-order theorem proving, which can enhance the proving efficiency of first-order theorem provers. Set implication modulo resolution, a principle of identifying the redundancy property of clauses, is proposed. The soundness of this principle in first-order logic without equality is proved, which means that eliminating clauses according to the principle has not effect on the unsatisfiability or satisfiability of original formulas. In addition, two novel preprocessing methods in first-order theorem proving are developed given the principle of set implication modulo resolution, i.e., set resolution subsumption elimination (SRSE) and set resolution asymmetric tautology elimination (SRATE). The soundness of the two clause elimination methods is also demonstrated. Finally, the effectiveness is theoretically compared between SRSE and resolution subsumption elimination (RSE) and between SRATE and resolution asymmetric tautology elimination (RATE), which shows SRSE and SRATE are more effective than RSE and RATE, respectively.
Combinatorial Test Sequence Set Reduction Approach for Railway Signaling Safety-Critical Software
RAO Chang, LI Nan, ZHANG Yadong, GUO Jin, LI Yao
2020, 55(3): 596-603. doi: 10.3969/j.issn.0258-2724.20190157
[Abstract](636) [FullText HTML] (254) PDF 781KB(10)
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When applying t-way combinatorial test sequence generation to a railway signaling system with large-scale inputs, test redundancy occurs, which causes high execution cost. Thus, a t-way combinatorial test sequence set reduction approach is proposed based on the greedy particle swarm optimization algorithm to reduce the cost. First, aiming at minimizing the test cost, an optimization model for t-way combinatorial test sequence set reduction is built. Then, on the basis of logic coverage of the test sequence sets, the greedy particle swarm algorithm is employed to solve the model and obtain the reduced test sequence sets. Finally, ZPW-2000 track circuit receiver software is used in a case study for the reduction of 2-way test sequence sets to validate the proposed approach. Results show that under the premise of 2-way coverage and logic coverage, the cost for a single test sequence set has decreased by up to 98.33% and the total cost for the test sequence sets has decreased by 36.10%, which indicates the feasibility and effectiveness of the approach.
Multi-objective Matching Optimization for Hybrid Fuel-Cell Power System in Trams
FU Wenchao, QI Hongfeng, DAI Chaohua, LI Mi, LIU Zhengjie, CHEN Weirong
2020, 55(3): 604-611. doi: 10.3969/j.issn.0258-2724.20180370
[Abstract](670) [FullText HTML] (249) PDF 1425KB(19)
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The hybrid power system configuration in fuel-cell trams greatly affects the vehicle dynamic performance, system efficiency and economic benefit. However, there is a lack of effective configuration optimization methods. To meet the objective of minimizing the cost in a vehicle service cycle, an optimal configuration method for fuel-cell hybrid power system is proposed on the basis of the traction power calculation in the dynamic conditions of trams. The multi-objective and multi-constraint optimization model of the fuel-cell hybrid power system is established with the minimum volume/weight and the minimum vehicle service cycle cost. Meanwhile, the dynamic demand, bus voltage, power source output, real time electric power balance, rates and depths of charge and discharge, and SOC (state of charge) of energy storage system are all taken into consideration. A Pareto front is obtained by the proposed method, and the optimal solution with the minimum cost and the acceptable volume/weight is also recommended. Finally, the simulation results show that the optimal hybrid fuel-cell power system configured by the proposed method can meet the design requirements, and the service cycle cost of the hybrid power system is reduced from 70 million yuan to 15 million yuan.
Methodologies of Pallet Allocation Over Pallet Pool in Intermodal Transportation Network
REN Jianwei, MENG Xiangdong, CHEN Chunhua, ZHANG Jin, ZHANG Xueyan
2020, 55(3): 612-619. doi: 10.3969/j.issn.0258-2724.20190340
[Abstract](490) [FullText HTML] (259) PDF 882KB(15)
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In order to solve the problems in pallet allocation of intermodal transportation network (ITN) over a pallet pool, by the use of non-linear programming, mixed-integer programming, and modified particle swarm optimization (PSO), the pallet allocation system were optimized in the cases of three available transport modes, i.e., shipping, highway, and railway. Firstly, the pallet allocation process was analyzed. Then, a mixed-integer non-linear optimization model for pallet allocation was built, in which the transit time, transit cost, handling batch, ratio of damaged pallets and time constraints were considered. Furthermore, the particle swarm optimization with inertia weigh (IPSO) and the particle swarm optimization with constriction factor (CPSO) were designed. Finally, the model and algorithm were verified by tests. The results show that compared with pallet transport through highway, the allocation cost could be reduced by 69.1% with pallet allocation in ITN. The IPSO outperforms the CPSO with the total allocation cost reduced by 1.82%. The larger the lead time of customer demand is, the more allocation cost can be saved by intermodal transportation. The transit time and cost of intermodal transportation affect pallet allocation decisions over a pallet pool.
Texture Depth Measured Method of Pavement Based on Static and Dynamic Anti-Sliding Characteristics
FENG Xingle, ZHANG Haiou, LI Wei, LIU Yamin, ZHANG Shaoyang
2020, 55(3): 620-627. doi: 10.3969/j.issn.0258-2724.20180282
[Abstract](661) [FullText HTML] (273) PDF 1310KB(12)
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The slippery surface of asphalt pavement is one of the leading major causes of traffic accidents. The mean texture depth (MTD) reflects the performance of skid resistance using a static texture of the pavement, while the friction coefficient reflects it through dynamic friction motion. Aimed to eliminate the difference between aforementioned two factors, a novel measurement method was proposed for effective texture depth. The point cloud data obtained by laser vision technology was studied. Firstly, B-spline was employed to interpolate the break-point of cloud data. Secondly, the concave points were removed according to the geometrical construction and anti-sliding mechanism of contact friction between the tire and road surface. Finally, the correlation between the MTD estimated by cross section method and data measured by the friction coefficient tester was analyzed. The results show that both the transverse and longitudinal MTD based on the proposed model could achieve stronger correlations with friction coefficient, compared with the traditional sand patch test. Their correlation values are 0.896 and 0.887, respectively, which are better than 0.504 of the sand patch test. The proposed method can implicitly reflect the dynamic friction coefficient through the static texture depth, and take full advantage of the high efficiency of the laser vision measurement and the objectivity of the friction coefficient, thereby achieve the desired balance of accuracy and efficiency.
Experiments on Material Proportions for Simulating Sandy Layer in Deep Sea
SHEN Xiang, YUAN Dajun, CAO Yutao, GAO Zhenfeng
2020, 55(3): 628-634. doi: 10.3969/j.issn.0258-2724.20180285
[Abstract](438) [FullText HTML] (304) PDF 639KB(13)
Abstract:
In order to obtain the material proportions that can simulate the sandy layer in the deep sea of Qiongzhou Strait, using on the orthogonal experiment method, the physical and mechanical parameters of different material proportions were analyzed with four control factors of barite powder/standard sand, binder concentration, silicon ratio and gypsum content. Firstly, standard sand or barite powder is used as aggregate, petroleum jelly and silicone oil as binders and gypsum powder as modifier. Secondly, 25 groups of material proportions were designed on the basis of orthogonal experiment principle, and types of tests of density, direct shear, compression and seepage were performed to obtain physical and mechanical indices such as weight density, internal friction angle, cohesion force, compression modulus, and permeability coefficient. Through the range analysis and significance analysis, the influence of control factors on the material parameters was explored, and a multivariate linear regression analysis of test results was carried to eliminate outliers. The results show that the weight density is most affected by the ratio of barite powder to standard sand; gypsum content is the leading factor to control the compression modulus; the internal friction angle and cohesion force have no major controlling factors; and the proportion of barite powder mainly affects the permeability coefficient. The appropriate material proportions for the sandy layer in deep sea environment are barite powder /standard sand of 0.4), binder concentration of 4.5%, silicon ratio of 3∶1, and gypsum content of 3%.
Mechanism and Kinetic Analysis on Degradation of Atrazine by UV/PS
LU Yixin, HE Yue, ZHANG Jianqiang, FU Chenchen, CHEN Jiao
2020, 55(3): 635-642, 680. doi: 10.3969/j.issn.0258-2724.20180523
[Abstract](557) [FullText HTML] (463) PDF 1140KB(25)
Abstract:
In order to deal with water pollution caused by atrazine (ATZ), the effects, mechanism, kinetics and pathway of ATZ degradation by ultraviolet/peroxodisulfate (UV/PS) were explored in terms of pH, UV intensity, PS concentration and temperature. The analysis of degradation mechanism indicates that UV could be photolyzed by UV and rapidly degraded by UV/PS in water. SO4−• and •OH coexisted in UV/PS system under neutral and weakly alkaline conditions. Kinetic analysis show that UV/PS degradation of ATZ fitted to quasi first-order reaction kinetics with differing temperature, pH, PS concentration and UV intensity. Degradation pathway analysis suggest that the main degradation pathways of ATZ were dechlorination, hydroxylation, deethylation and deisopropyl, all of which were correlated; yet the triazine ring was notoxidized and opened. The results show that the degradation rate of 2.5 μmol/L ATZ by UV/PS system was 91.03% when the system temperature, PS concentration, UV intensity, initial pH value and response time was 25 ℃, 70 μmol/L, 50 mW/cm2, 5.8 and 20 min, respectively.
Experiments on Mechanical Performance of Tibetan Rubble Stone Walls Retrofitted with BFRP Grids
HUANG Hui, YANG Dan, CHEN Ke, JIA Bin
2020, 55(3): 643-649. doi: 10.3969/j.issn.0258-2724.20180455
[Abstract](570) [FullText HTML] (302) PDF 1158KB(15)
Abstract:
Two groups of Tibetan rubble stone walls, each with four pieces, were tested under compressive loading and low cyclic loading, respectively, in order to study the mechanical performance of the walls retrofitted with basalt fiber reinforced polymer (BFRP) grids. These tests focus on the mechanical behavior, failure modes, load carrying capacity, energy dissipation capacity, and stiffness degradation of the walls. The experimental results demonstrate that the rubble stone walls retrofitted with BFRP grids showed slower crack development compared with the un-retrofitted walls under the same compressive load. The measured average compressive strength of the rubble stone walls retrofitted with BFRP grids was about 2.72 times that of the un-retrofitted walls. The typical compressive failure mode of the rubble stone walls retrofitted with BFRP grids was BFRP grids rupture followed by out-of-plane buckling failure. Meanwhile, the rubble stone walls retrofitted with BFRP grids showed higher energy dissipation capacity and shear strength than the un-retrofitted rubble stone walls, and the measured average shear strength increased by 74.3%. Under low cyclic loading the rubble stone walls retrofitted with BFRP grids showed BFRP grids rupture along the diagonal cracks followed by shear failure.
Formation Mechanisim of Rail Corrugation Occurring on Tight Curved Track with Vanguard Fasteners
WU Bowen, CHEN Guangxiong, ZHAO Xiaonan, ZHU Qi, KANG Xi
2020, 55(3): 650-657. doi: 10.3969/j.issn.0258-2724.20180371
[Abstract](622) [FullText HTML] (283) PDF 1180KB(23)
Abstract:
In order to study the formation mechanism and countermeasures of the rail corrugation on a tight curved track with vanguard fasteners. First, a self-excited vibration finite element model consisted of the leading wheelset and the track system was established based on the viewpoint of friction-induced vibration causing rail corrugation. The dynamic stability of the wheelset-track system was analyzed using the complex eigenvalue method. Then, the dominant factors affecting the rail corrugation were found through the parameter sensitivity analysis, and the countermeasures to suppress or eliminate the rail corrugation were put forward. The results show that the self-excited vibration of the wheelset-track system at 319 Hz induced by the saturated creep force between the wheel and the rail is the main cause of severe rail corrugation on the inner rail. The corrugation wavelength predicted by the model is 51.4 mm, which is closed to the measured data. The parameter sensitivity analysis shows that the modulus of elasticity and damping coefficient of the rubber rest pad in the vanguard fasteners have a great influence on the rail corrugation, the larger the elastic modulus and damping coefficient are, the lower the probability of rail corrugation occurrence is. The rubber rest pad with high modulus of elasticity and damping coefficient is beneficial to the suppression or even elimination of the rail corrugation. when the damping coefficient of the rubber rest pad is above 0.000 1, the rail corrugation can significantly be alleviated.
Influences of Foreign Object Damage on Fatigue Strength of 25CrMo4 Axle Alloy Steel
WU Shengchuan, XU Zhongwei, KANG Guozheng, HE Weifeng, DAI guangze
2020, 55(3): 658-663. doi: 10.3969/j.issn.0258-2724.20180308
[Abstract](625) [FullText HTML] (290) PDF 1252KB(9)
Abstract:
To study the correlation between the foreign object damage (FOD) and the fatigue strengh of alloy steel 25CrMo4, the simulated test for FOD of high speed railway axle steel specimens was carried out by a compressed-gas gun device. Firstly, the FOD defects were simulated on railway axle steel specimen surfaces. Secondly, the fatiuge S-N curves of smooth and FOD specimens were obtained from rotating bending fatigue tests. Furthermore, the stress concentration factor was evaluated for different types of defects by elastic finite element method (FEM). The fatigue limit and fatigue notch coefficient (FNC) of FOD specimens were calculated based on Peterson formula. The results show that the fatigue performance of FOD specimens is considerably lower than that of smoothed ones, the higher the impact velocity, the lower the fatigue performance. The FNC of edge defect specimens is the largest (about 1.52) while the smallest (about 1.14) for plane defect specimens, thus leading to a larger dispersion in lifetime. Compared with the experiments, theoretical evaluation and FEM method can obtain relatively conservative results in fatigue strength.
Bionic Design Method for Crane Box Girder Wind Load Reduction Based on Ostracion-Cubicus
WANG Yupu, CHENG Wenming, DU Run, WANG Shubiao, DENG Yong
2020, 55(3): 664-671. doi: 10.3969/j.issn.0258-2724.20190085
[Abstract](589) [FullText HTML] (233) PDF 1743KB(10)
Abstract:
The wind load is an important load during the gantry crane operation, and the crane box girder is the major windshield component . Therefore the wind load reduction design for the crane box girder can decrease the crane energy consumption effectively. The bionic design method for the crane box girder wind load reduction based on the geometry of ostracion-cubicus was explored. Firstly, the ostracion-cubicus mouth feature profile was extracted through gray level conversion, binary image conversion and edge detection method. On this basis, a bionic model was built with the box girder height as the design variable. Secondly, the bionic design of the traditional crane box girder was realized by attaching the light material to the windward side of the box girder. Finally, aerodynamic characteristics of the bionic box girder was evaluated with FLUENT. A 40 t container crane was taken as an evaluation case, and comparison was made between the original and the bionic ones, expanded polystyrene (EPS) was selected as the attachment material. The research shows that the wind load decreases by 65.77% with the bionic girder , while the weigh is only 2.28% more than the original one. The flow field disturbance from the boundary layer separation reduces due to the streamlined structure of the bionic girder, which decreases the lift pulsation, improves the running stability of the crane in the wind field.
Penalty Parameter Selection Method for Variational Mode Decomposition and Time-Varying System Identification
JIN Hang, LIN Jianhui, CHEN Xieqi
2020, 55(3): 672-680. doi: 10.3969/j.issn.0258-2724.20190357
[Abstract](584) [FullText HTML] (339) PDF 1939KB(24)
Abstract:
As the penalty parameter in the variational mode decomposition (VMD) affects the decomposition performance, a penalty parameter selection method is proposed on the basis of data driven. The method firstly determines the penalty parameter at the main peak by using the Fourier transform. Then the mode parameters are adjusted to obtain the finite number of intrinsic mode function components. The pseudo component is eliminated by comparing the natural frequencies and damping ratios of the components under different mode parameters. Finally, the true intrinsic mode function components are processed with Hilbert transform to identify the instantaneous frequency of a time-varying system. In order to prove the validity and accuracy of the proposed method for time-varying system identification, the time-varying work processes of a structural system with time-varying stiffness and a diesel engine are studied respectively. The results of the proposed method are compared with those of the empirical mode decomposition method. The results show that when the penalty parameter is 1.5 to 16.0 times the maximum signal amplitude, the optimal decomposition results will be obtained. The proposed method can more accurately identify the instantaneous frequency, and be used for instantaneous frequency identification in engineering applications.

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