• 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. 1

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2020, 55(1)
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Abstract:
Key Technologies in Visualized Intelligent Management Platform for Life Cycle of Wind Power Systems
ZHU Qing, ZENG Haowei, XIE Xiao, ZHANG Yeting, JIANG Jie
2020, 55(1): 1-8. doi: 10.3969/j.issn.0258-2724.20180721
[Abstract](678) [FullText HTML] (330) PDF 12306KB(51)
Abstract:
For years, each sector in the wind farm life cycle has used separate management systems, which results poor data sharing and low levels of intelligent automation. It is difficult to achieve comprehensive and efficient management of whole space and full information in wind power systems. To deal with this problem, we analyzed the relationship and characteristics of geographic environments data, facilities, and all sector operations in wind power systems, study the key technologies of different types of spatio-temporal data sharing, multi-sector and multi-service collaboration, and visualized intelligent management in the life cycle of wind power systems. A visualized intelligent management platform based on the 3D GIS (geographic information system) technology was designed and developed. This platform includes functional modules such as real-world data management, planning and design management, dynamic construction supervision, and intelligent operation and maintenance management. It integrates various professional applications and runs through the life cycle in wind power system, and provides efficient decision support for the collaborative planning, construction, operation and maintenance of wind power systems. The platform is tested and verified by a typical wind farm.
Reliability Optimization of Co-phase Power Supply Device Based on Frequency Conversion Control Strategy
CHEN Minwu, TIAN Hang, SONG Yalin, CHEN Ling
2020, 55(1): 9-17. doi: 10.3969/j.issn.0258-2724.20180668
[Abstract](590) [FullText HTML] (265) PDF 1495KB(23)
Abstract:
Co-phase power supply technology can effectively deal with the obstacles in neutral-section passing and power quality common for the traction power supply system. In order to ensure the safe and reliable operation of co-phase power supply systems, the reliability optimization of the co-phase power supply device is very important due to its crucial role in the whole system. Thus, a reliability evaluation model is established in view of the special converter topology. Further, how traction load characteristics and main electrical parameters affect device reliability is analyzed. This work finds that altering switching frequency of the converter in different load sections can effectively reduce the failure rate of power components. The variable frequency control optimization model is established with the lowest failure rate of power modules. The optimal frequency conversion control strategy is obtained by the hybrid genetic algorithm-particle swarm optimization (GAPSO). Finally, an engineering prototype applied in Center-South Shanxi Railway is used for data measurement and comparative analysis, indicating that by the use of the frequency conversion control strategy, the device lifetime can be increased by 20.90%, and the growth rate of reliability can reach 54.17%. This proves that the frequency conversion control strategy can effectively improve the reliability of the co-phase power supply device.
Recognition Method for Multi-scale Sparse Power Quality Disturbance
ZHU Yunfang, WU Zhiyu, GAO Yan, HOU Yishuang, LIU Zhengjie
2020, 55(1): 18-26. doi: 10.3969/j.issn.0258-2724.20180606
[Abstract](550) [FullText HTML] (234) PDF 1071KB(14)
Abstract:
In the traditional power quality disturbance recognition, there is a large amount of data and disturbance characteristics are dependent on subjective selection. To deal with these problems, a recognition method for multi-scale sparse power quality disturbance is proposed. Firstly, a multi-scale sparse model for power quality signal is constructed. Through the stationary wavelet transform (SWT) for the disturbance signal, its low and high frequency information is obtained. Then by compressed sampling for the disturbance signal, the dimension reduction data are obtained. Further, sparse coefficients calculated by orthogonal matching pursuit (OMP) algorithm constitute a sparse vector, which is directly inputted into the deep belief network to achieve intelligent disturbance classification. Meanwhile, to improve the recognition rate, cross-entropy algorithm is applied to find the optimal parameters such as the number of hidden layers and learning rate. Finally, in order to verify the effectiveness of the proposed method, a large number of simulation tests were performed for several typical single disturbances and mixed disturbances. The simulation results demonstrate that in the ideal environment the averaged recognition rate of this method for seven typical single disturbances and thirteen mixed disturbances is 99.0% and 97.69% respectively, and in noisy environment at least 96.71% and 94.62% respectively, which shows that the proposed method has a desirable performance in disturbance identification.
Traction Load Classification Method Based on Improved Clustering Method
ZHANG Liyan, CHEN Yingyue, HAN Zhengqing
2020, 55(1): 27-33, 40. doi: 10.3969/j.issn.0258-2724.20180513
[Abstract](553) [FullText HTML] (228) PDF 803KB(10)
Abstract:
In order to obtain more accurate traction load classification, based on a large amount of measured traction load data, an improved fuzzy C-means clustering method is proposed, which can automatically obtain the best classification number. A charged effective coefficient, the maximum value, the average value, the value of 95% and one to five order moments were chosen as clustering indicators to classify feeder current. Then the probability density function of traction loads was fitted using non-parametric kernel density estimation, and the probability distribution model of each feeder current type was obtained. The results show that the characteristic parameters and probability distributions of the traction loads that were clustered together are.
Review on Network Virtualization Simulation Software
WANG Yingshu, WANG Xu, ZUO Yu, LIU Qing, ZHANG Juanjuan, YUAN Shu, YU Fucai
2020, 55(1): 34-40. doi: 10.3969/j.issn.0258-2724.20190556
[Abstract](641) [FullText HTML] (307) PDF 576KB(37)
Abstract:
Network virtualization simulation software (NVSS) is an integration of network virtualization and virtualization software, serving as an important auxiliary tool for network engineers in learning and training, and researchers in experimental verification. It realizes the virtualization of network equipment on the host through virtualization technology, which helps to build and configure user-defined network topology. In order to help users choose the suitable NVSS as desired, this paper systematically introduces its birth and development as well as domestic and foreign research status, based on relevant research literature and the evolution of software architecture and technology. Furthermore, representatives of NVSS in different periods, such as graphical network simulator 3 (GNS3) and emulated virtual environment-next generation (EVE-NG), are listed with a focus on the functions, performances, properties, characteristics and application scope. Finally, the prospects of NVSS technology and demand are discussed. NVSS will be characterized by compatibility, interactivity and intelligence, and may be applied in various industries.
Passenger Flow Prediction for Guangzhou-Zhuhai Intercity Railway Based on SARIMA Model
LI Jie, PENG Qiyuan, YANG Yuxiang
2020, 55(1): 41-51. doi: 10.3969/j.issn.0258-2724.20180617
[Abstract](684) [FullText HTML] (363) PDF 1445KB(56)
Abstract:
To achieve the short-term prediction on the railway passenger flow and analyze the influence of prediction step on prediction accuracy, firstly, the characteristics and variation of passenger flow for Guangzhou-Zhuhai intercity railway were analyzed. Then, considering the passenger flow characteristics, a prediction model based on the seasonal autoregressive integrated moving average (SARIMA) was built with the Statsmodels module in Python. Next, the model performance was validated on different prediction steps. The conclusion shows that when the prediction step is 1, the mean absolute percentage error (MAPE) for Guangzhou South station, Xiaolan station and Zhuhai station is 3.97%, 5.83%, and 5.43%, respectively; when the prediction step increases to 2, the MAPE shows an increase trend, which is 5.31%, 6.79%, and 7.62% for Guangzhou South station, Xiaolan station and Zhuhai station, respectively; when the prediction step exceeds 2, the MAPE is stable. In addition, comparative results with other passenger flow prediction methods, i.e., random forest (RF), support vector machine (SVM), gradient boosting (GB), and K-nearest neighbor (KNN) demonstrate that when the prediction step is 1, the SARIMA model performs slightly better; when the prediction step exceeds 2, the MAPE of RF, SVM, GB, and KNN increases dramatically, amounting several times that of the SARIMA model. Finally, the experiment results show that the SARIMA model can achieve a better performance than other models in terms of the multi-step prediction for passenger flow time series.
Design Method of Hydraulic Valve Block for Tunnel Boring Machine
ZHANG Huailiang, ZHAO Lina, ZHOU Jingxing
2020, 55(1): 52-59. doi: 10.3969/j.issn.0258-2724.20180072
[Abstract](518) [FullText HTML] (249) PDF 1429KB(13)
Abstract:
In order to improve the flow quality of flow channels in hydraulic valve block under foundation vibration, a simulation model of flow channels under foundation vibration was established based on finite element theory and the correctness of the simulation model was verified. The effects of the different flow channels layout, process holes structure parameters, import and export flow length on the pressure drop characteristics of flow channels were analyzed under the foundation vibration. The design flow of hydraulic valve block under the foundation vibration was put forward. The results show that the U-shaped flow channel has the best pressure drop characteristics and Z-shaped has the worst pressure drop characteristics under the foundation vibration; the shorter U-shaped groove hole length is, the smaller the pressure drop average and the pressure drop fluctuating is; when the length of Z-shaped flow channel fabrication hole is 3.5 times the diameter of fabrication hole, the length of V-shaped flow channel fabrication hole is 3 times the diameter of fabrication hole, the average and fluctuating of pressure drop are less; it is helpful to reduce the impact of foundation vibration when the diameter of fabrication hole is bigger than the diameter of import and export flow channel; when the length of the export flow channel is over 3 times the diameter of export flow channel, it is beneficial to avoid recovery area after the outlet flow channel in turn flow field. The new method can effectively reduce the pressure drop in valve block and improve the pressure stability.
Method of Using Flat Plate as Calibration Tool for Robot Tool Center Point Calibration
HAN Fenglin, LI Peng, TAN Donghe, LI Dan, SHAO Dongshi, YAN Hongzhi
2020, 55(1): 60-67. doi: 10.3969/j.issn.0258-2724.20180807
[Abstract](638) [FullText HTML] (257) PDF 986KB(36)
Abstract:
To obtain the tool center point (TCP) parameters readily and accurately in the industrial field and reduce the positioning error of robot end tools, a robot TCP calibration method utilizing a flat plate as calibration tool is proposed. The robot TCP parameter calibration model is established under the constraint that the space contact points between the robot TCP and the flat should be coplanar. In the cases of unknown and known TCP nominal parameters, based on the particle swarm optimization (PSO) algorithm, the direct solution and linearization deviation solution algorithms for TCP are put forward respectively. The feasibility and accuracy of the proposed methods are verified by numerical simulation and calibration experiment. Compared with the traditional four-point calibration method, the error of TCP direct solution and deviation solution algorithm is less than 0.5 mm and 1.0 mm, respectively. The calibration method proposed is simple and easy to implement, and possesses high calibration efficiency and precision.
Temperature Rise Characteristic Analysis and Liquid Cooling Structure Design of Lithium Battery
PAN Chaofeng, LIU Bing, CHEN Long, HE Zhigang, HAN Chao
2020, 55(1): 68-75. doi: 10.3969/j.issn.0258-2724.20180241
[Abstract](642) [FullText HTML] (263) PDF 1821KB(20)
Abstract:
Concerning the phenomenon of uneven temperature distribution and excessive temperature of power battery heat generation in electric vehicles, the thermal analysis model of the battery package was established on the basis of thermal physical parameters of the battery and internal resistance at different temperatures. The bus current value of the electric vehicle collected by the test was fitted, and then the temperature rise of the battery package in different driving speeds could be obtained by the simulation. Finally, the vehicle test on typical urban conditions was conducted to measure the temperature rise dates of the test points in the battery package at different constant speeds, and then the curves were fitted by the temperature rise dates. The comparisons between the simulation and the test verified that the thermal analysis model was accurate and effective. On the basis, the double inlet and double outlet liquid cooling pipe structure scheme was designed to analyze the cooling effect of the liquid cooling scheme at the 1C discharge rate. The results show that the internal resistance of lithium battery is only 13.9 mΩ at high temperature (50 ℃), while it reaches 21.5 mΩ at low temperature (−30 ℃); the maximum temperature rise of electric vehicle under new European driving cycle (NEDC) and constant speed conditions (40, 50, 60, 70 km/h) reach 1.8, 2.6, 3.6, 5.3, and 8.0 ℃ respectively; the U-shaped structure liquid cooling pipe can reduce the temperature rise of battery pack effectively and improve the temperature uniformity of the battery pack.
Temperature Field of in-Wheel Motor Using Coupled Multi-physics Domain Solution
ZHANG Heshan, XU Jin, DENG Zhaoxiang, JIANG Yanjun
2020, 55(1): 76-83, 91. doi: 10.3969/j.issn.0258-2724.20170263
[Abstract](620) [FullText HTML] (255) PDF 1406KB(24)
Abstract:
In order to study the influence of temperature change on the working performance and service life of in-wheel motor for electric vehicles, a coupled multi-physics analysis method is proposed. Firstly, the field-circuit coupling method is used to solve the finite element model of the in-wheel motor and the external circuit. A joint simulation model including the in-wheel motor and external drive control circuit is established, which takes into account the influence of the time harmonic current from external excitation on the magnetic field. Then, the calculated winding copper loss, stator core loss, permanent magnet (PM) eddy current loss and stray loss are used as heat sources, and they are coupled to each component by magneto-thermal coupling method to study the transient temperature field. The transient variation characteristics of the loss distribution in time and space are overall considered, and the thermal loss and temperature field are coupled accurately in real time. The temperature variation of each component over time and space is studied in detail. The direct coupling between electromagnetic field and external circuit, and the sequential coupling between electromagnetic field and temperature field are realized by the coupled multi-physics analysis method. Finally, the bench test of the in-wheel motor is carried out. The results show that the maximum temperature error between the simulation and tests is 4.96% under rated conditions, and the maximum error is 10.55% under peak conditions.
Effect of Rolling Direction on Contact Fatigue Damage of CL60 Wheel Steel
HU Yue, LI Qun, LIU Qiyue, GUO Jun, WANG Wenjian
2020, 55(1): 84-91. doi: 10.3969/j.issn.0258-2724.20180073
[Abstract](526) [FullText HTML] (238) PDF 1747KB(16)
Abstract:
In order to investigate the effect of wheel rolling direction on rolling contact fatigue (RCF) damage of wheel steel, the rolling-sliding wear experiments under both unidirectional and bidirectional conditions were carried out on a rolling wear testing apparatus (WR-1, China). The wheel surface damage, section fatigue crack morphology and wear debris size were observed by optical microscope and scanning electron microscope, the evolution law of wheel surface damage, fatigue crack propagation and debris size with the number of reverse cycles under reversing operating conditions were investigated. The results show that the wheel surface damage is mainly caused by peeling. As the number of reverse cycles increases from 10 000 to 120 000, the initial peelings gradually wear off and then new peelings are formed opposite to the original rolling direction, changing wheel rolling direction is beneficial to reduce the RCF damage of wheel materials under the same test cycles. The propagation direction of surface microcracks is changed after wheel reverse rolling, forming reverse fatigue cracks of 4°−8°, and crack distortion and branching occur on the wheel samples. As the number of cycles increases, the debris size increases firstly and then decreases under unidirectional condition, after wheel reverse rolling, the debris thickness increases firstly and then decreases, the thickness increases to 10−12 μm after reversing 10 000 cycles, which is twice as much as under the unidirectional condition.
Study on Reinforcement for Fatigue Cracking of Rib-to-Diaphragm Welded Joints of Steel Bridge Deck
ZHANG Qinghua, JIN Tong, LI Jun, BU Yizhi
2020, 55(1): 92-99. doi: 10.3969/j.issn.0258-2724.20170744
[Abstract](566) [FullText HTML] (307) PDF 1493KB(17)
Abstract:
In order to study the reinforcement effects of bolted angle steel on fatigue cracking of the orthotropic steel bridge deck, the full-scale test model was used to study the reinforcement effect of fatigue cracks on the rib-to-diaphragm welded joints. A finite element model with fatigue cracks was established using ANSYS, and to study the reinforcement effects under different length of fatigue cracks conditions based on the fracture mechanics theory. The results indicate that the fatigue cracks initiate from the toe of longitudinal rib-to-diaphragm welded joints and expand along the longitudinal web, the reinforcement method with bolted angle steel can reduce the main tensile stress of the key measure points at the cracking details and the strain of measure points at crack tips by 56% and 80%, respectively. The stress intensity factor of the crack tip is reduced by more than 80% after bolting angle steel reinforcement, and crack propagation rate is reduced significantly. For the different lengths of fatigue cracks before the longitudinal rib webs, the amplitude of the crack tip stress intensity factor is reduced by 60%−90% using the reinforcement method, but with the increase of the fatigue cracks length, the reinforcement effects are reduced continuously, the reasonable selection of the reinforcement time is one of the key factors in the reinforcement effects.
Transverse Seismic Pounding Effect and Pounding Reduction of Simply-Supported Girder Bridge for High-Speed Railway
YANG Menggang, MENG Dongliang, WEI Kanghua, QIAO Jiandong
2020, 55(1): 100-108. doi: 10.3969/j.issn.0258-2724.20180277
[Abstract](560) [FullText HTML] (303) PDF 1426KB(26)
Abstract:
A 32 m standard-span simply-supported girder bridge with 7 spans for high-speed railway was used as a prototype to study the effects of the earthquake-induced transverse pounding, as well as the pounding reduction effects of various isolation devices. The actual force-deformation curves of shear keys were determined experimentally and a finite element model considering pounding was established using SAP2000. On this basis, influences of the rail system, the initial gap between the shear keys and bearing padstones, and the thickness of shear-key plates on seismic responses of the bridge were analyzed. Then, the pounding reduction effects of rubber bumpers, lead rubber bearings (LRBs), friction pendulum bearings (FPBs), high damping rubber bearings (HDRs), and fluid viscous dampers were discussed. The results are as follows: the rail system can significantly alter the distribution of seismic forces between bridge spans. Under excitations of the maximum earthquakes considered, the nonlinear effect of shear keys is significant, with the maximum pounding force of 2.18 MN. For the sample bridge presented in this paper, it is a reasonable configuration to set the initial gap between the pounding members as 3 cm and the thickness of shear-key plates as 32 mm. The seismic isolation devices can improve the seismic performance of the bridge; their pounding reduction effects are affected by spectral characteristics of ground motions as well as their own mechanisms. Among them, the FPB has better applicability and the seismic forces between different spans become more uniform after the installation of FPBs.
Time-Frequency Characteristics of Box-Girder Vibration and Noise Based on Wavelet Transform
ZHANG Xun, ZHAO Yu, RUAN Linghui, LIU Rui, LI Xiaozhen
2020, 55(1): 109-117. doi: 10.3969/j.issn.0258-2724.20170768
[Abstract](574) [FullText HTML] (264) PDF 5469KB(15)
Abstract:
In order to explore time-frequency characteristics of train-induced box-girder vibration and noise, a simply-supported concrete box-girder with a span of 32 m was selected as the case, the vibration and near-field noise of the box-girder slabs were measured, and the signals were processed by using wavelet transform with the modified Littlewood-Paley (MLP) wavelet basis. Two indexes of wavelet ridge curve and wavelet energy ratio were introduced to quantitatively analyze time-frequency characteristics. On this basis, how train speed and driving direction affect time-frequency characteristics were discussed. The results show that compared with the Morlet basis and the Mexihat basis, the MLP basis can better depict the localization of box-girder vibration and noise in both time and frequency domains. Box-girder noise has less variation in frequency than the vibration, and the former’s wavelet energy is more concentrated in frequency domain. The variation of flange vibration and web vibration in frequency domain are sensitive to train speed and driving direction, respectively. The frequency range of 45 to 60 Hz is vital for box-girder noise mitigation.
Reconstruction Method of Shear Keys on Existing Bridges Based on Structural Fuse Concept
XU Lueqin, WANG Long, LI Jianzhong, LI Zhongxiong
2020, 55(1): 118-125, 143. doi: 10.3969/j.issn.0258-2724.20180425
[Abstract](629) [FullText HTML] (257) PDF 1631KB(20)
Abstract:
Shear keys in existing bridges are ineffective in controlling the seismic displacement due to the lack of design codes to guide the details of construction and reinforcement. To improve the ability of existing bridges to resist earthquake damage, the reconstruction of shear keys based on the structural fuse concept is proposed. Firstly, quasi-static experiments are conducted to verify that the shear keys with a particular design of structural configuration and reinforcement meet the requirements of the structural fuse concept. Then, a prediction model is proposed to calculate the strength of shear keys based on the sliding shear mechanism, and the detailed procedures are presented for the reconstruction of shear keys. Finally, numerical simulations according to an actual bridge are performed to comparatively examine the effects of displacement control and force transfer of the reconstructed shear keys. The results show that the failure of reconstructed shear keys in a ductile mode with sliding shear and a large sliding displacement, causes no damage to the cap beam/stem wall. The strength of shear keys can be predicted accurately with a unified equation for different design parameters. The prediction errors of the equation are lower than 10% and most of them lower than 5%. Numerical simulations reveal that under the earthquakes of E1 and E2 levels, the reconstructed shear keys can decrease the lateral displacement of superstructure by 13.5% and 22.0%, respectively, and reduce the transverse deformation of laminated rubber bearings by 83.1% and 45.8%, respectively. The reconstructed shear keys remain perfectly elastic under the earthquake of E1 level and experience strength degradation under the earthquake of E2 level, which plays the role of structural fuse.
Analysis of Seismic Fragility and Recoverability of Long-Span Cable-Stayed Bridge
WU Fangwen, MENG Yuanying, CHEN Yue, JI Quanyou, YANG Yuanyuan, WU Zhida
2020, 55(1): 126-133. doi: 10.3969/j.issn.0258-2724.20180449
[Abstract](590) [FullText HTML] (264) PDF 1067KB(24)
Abstract:
To study the seismic capacity of the main tower of cable-stayed bridge under earthquake and evaluate its seismic recoverability, the structural dynamic calculation model was established by the finite element analysis program SPA2000 based on a single-column long-span concrete cable-stayed bridge, the seismic response of the transverse cable-stayed bridge was analyzed by incremental dynamic analysis (IDA). The moment-curvature curves of the tower key sections were studied and the curvature damages were calibrated by analysis software X-TRACT, then the data from IDA analysis were processed, and the seismic vulnerability curve of each key sections of the main tower was obtained, and the vulnerable part of the main tower and its evolution law were determined. Based on the concept of recoverability, the seismic restorability analysis of the structure was carried out. The results show that under the action of transverse seismic, the bottom section of the tower is the vulnerable section. When the action of seismic intensities are 0.150g and 0.271g, its own seismic capacity decrease from 80.6% to 46.7%, with the increase of seismic intensity, the bridge’s seismic reserve capacity decrease.
Refined Study on 3D Flow Characteristics around Bridge Piers
YANG Wanli, WU Chengwei, ZHU Quanlong, WANG Guangjun
2020, 55(1): 134-143. doi: 10.3969/j.issn.0258-2724.20180335
[Abstract](602) [FullText HTML] (235) PDF 1898KB(25)
Abstract:
In order to investigate into the characteristics and mechanism of the current forces on bridge piers, a refined study on 3D flow around the typical pier model was conducted considering the influence of the free surface. ANSYS FLUENT was employed to address the characteristics of the drag force and lift force on the whole pier model. The pier model was divided into five sections from the bottom to top of the cylinder, characteristics of the drag and lift forces on each section were compared, and the variation law of the drag and lift forces along the water depth was analyzed. Further, the influences of the free surface and the bottom condition on vortex structure were analyzed and the relationship between 3D flow field and current force was discussed. Results show that the current force on pier is not uniformly distributed along the water depth; i.e., the mean value of drag force on cylinder sections c1−c4 accounts for 25%, 30%, 25% and 20%, respectively, of the total drag force on pier, and c5 contributes almost zero due to its exposure to air. The amplitudes of the drag and lift forces in the middle-lower part are larger than those at the bottom, middle-upper, and free surface parts of the water depth. Besides, the alternating vortex shedding causes alternating fluctuations of the free surface at the left and right sides of the cylinder. The free surface suppresses the vortex shedding, and vortices of different scales exist at the free surface, which are quite different from the two alternately shedding vortexes under the free surface. The vortex shedding at the middle-lower part of the pier lags behind the rest parts, resulting in a significant phase difference in the lift force at different parts of the cylinder. The lift force is comparable in magnitude to the average value of the drag force, for example which are respectively 5.511 N, 3.695 N in case 3, showing that the possible vibration of the pier or bridge caused by the lift force cannot be ignored.
Levenberg-Marquardt Algorithm for Orthogonal Fitting of Transition Curves
SONG Zhanfeng, WANG Jian, LI Jun
2020, 55(1): 144-149. doi: 10.3969/j.issn.0258-2724.20190130
[Abstract](942) [FullText HTML] (231) PDF 1202KB(23)
Abstract:
To identify the parameters of transition curves in as-built alignments by measured points, orthogonal least-squares fitting is studied on the basis of the parameter equation of transition curves. First, eigenvalue analysis has clarified that the Gauss-Newton (GN) algorithm usually fails to converge because of the existence of the ill-condition. Next, a bi-objective optimization model is proposed and the Levenberg-Marquardt (LM) algorithm combining the GN algorithm with the steepest descent method is constructed to fit a transition curve to points orthogonally. The LM parameter is updated dynamically during iterations according to the evaluation of the distance between the current and the optimum locations. Finally, Monte Carlo simulations are employed to test the performances of the GN and LM algorithms with measured points and the same 5 000 initial values. Experimental results show that the GN algorithm diverges while the LM algorithm converges to the same optimum under different initial values. The number of iterations, with an average of 16.8 times and the minimum of 5 times and the maximum of 50 times, is related to the distance between the initial and the optimum locations. The LM algorithm shows a better robustness than the GN algorithm.
Method of Force-Finding Analysis Based on Ratio Updating for Cable Domes
JIANG Zhengrong, LIU Xiaowei, SHI Kairong, LIN Quanpan
2020, 55(1): 150-157. doi: 10.3969/j.issn.0258-2724.20180201
[Abstract](497) [FullText HTML] (264) PDF 821KB(13)
Abstract:
In order to determine the prestress distribution of cable domes efficiently, a new method of force-finding analysis based on ratio updating was proposed. In this method, values of cable prestresses are pre-assumed and then constantly adjusted according to the continuously updated ratio of cable prestress; the precise prestress distribution of cable dome is acquired by iterations using the cable force and geometric shape as convergence control parameters. In this way, a force-finding analysis of cable domes is first conducted without considering the gravity effect, which verifies the effectiveness of this method. When the gravity is considered, each cable segment is divided into multiple units. An invariant, the cable force’s horizontal component along the length is introduced and the ratio of cable force is then replaced by that of the horizontal component force to deal with the situation with gravity. The results show that the method of force-finding analysis based on ratio updating is characterized by fast computational speed, small geometric shape deviation, and high precision. The results of force-finding analysis considering the influence of gravity are significantly different from those without considering gravity, and the maximum deviation reaches 19.34%. Thus, the influence of gravity should be taken into account in force-finding analysis of cable domes. In addition, whether each cable segment is divided into one unit or multiple units, the results of force-finding analysis make little difference (0.05% maximum deviation). Therefore, in cases when the cable prestress is large and cable length is short, each cable segment could be divided into only one unit to simplify the solving process of prestress distribution.
Analysis for Displacement Response Characteristics of Complex Multi-layer Base-Isolated Structure under Near-Field Ground Motion
FANG Dengjia, DU Yongfeng, LIU Chengqing, DENG Youyi
2020, 55(1): 158-166, 192. doi: 10.3969/j.issn.0258-2724.20181038
[Abstract](707) [FullText HTML] (260) PDF 2020KB(16)
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In order to study the influence of near-field ground motion characteristic parameters on the seismic displacement response of a super-long complex base-isolated structure, firstly the correlation among 128 near-field ground motion characteristic parameters was analyzed. Then, the near-field ground motions were inputted into the super-long complex base-isolated structure. The correlation degree and variation characteristics between the characteristic parameters of impulsive and non-impulsive ground motions and structural displacement response were analyzed. The results show that the long period of the base-isolated structure is close to the velocity sensitivity range in the velocity spectrum, but far from the acceleration sensitivity range in the acceleration spectrum, such that the displacement response is more correlated with the peak ground velocity (PGV) rather than peak ground acceleration (PGA). The peak ground displacement (PGD) and input energy have greater influence on the inter-story displacement of lower floors than on that of higher floors, while the PGV and PGA have less influence on the inter-story displacement of lower floors than on that of higher floors. The correlation degree between other characteristic parameters and the inter-story displacement response of the base- isolated structure is consistent with the correlation degree between the corresponding characteristic parameters and input energy (or PGV). Under the near-field earthquake, the displacement of the isolation bearing at the end and corner of the structure is obviously larger than that at the center. Impulsive ground motion magnifies the inter-story displacement and isolation layer displacement by 56.59% and 58.33% respectively, and the magnification effect on the inter-story displacement of lower floors is more obvious.
Static Bearing Capacity Analysis of CFRP-Reinforced Short CHS Steel Tubular Columns under Axial Compression
SHAO Yongbo, ZHU Hongmei, YANG Dongping
2020, 55(1): 167-174. doi: 10.3969/j.issn.0258-2724.20180527
[Abstract](519) [FullText HTML] (236) PDF 1463KB(9)
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To predict the ultimate strength of a short circular hollow section (CHS) steel tubular columns reinforced with carbon fibre-reinforced polymer (CFRP), both theoretical and numerical analyses were carried out. In the theoretical analysis, based on equivalent section method, the equations for calculating the load bearing capacities of CHS steel tubular columns under axial compression are deduced, which correspond to two different reinforcing methods, in which CFRPs are arranged in circumferential placement and in longitudinal-circumferential placement. In the numerical analysis, both eigenvalue buckling method and Riks method are combined to build a nonlinear finite element model of the tubular columns under axial compression. The finite element analysis for the stress distribution of the longitudinal and circumferential CFRPs shows that the circumferential CFRPs are under tension and restrain the radial deformation of the tubular columns, while the longitudinal CFRPs share the axial compression and restrain the deformation of the tubular columns. The comparison of the numerical results, theoretical results and reported experimental results show that the maximum deviation among them is no more than 2%, which verifies the finite element model and deduced equations.
Flexural Behavior of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced Polymer under Hydrothermal Environment
JIANG Shenghua, YAO Guowen, LIU Chaoyue, LIU Xiaochun
2020, 55(1): 175-183. doi: 10.3969/j.issn.0258-2724.20170893
[Abstract](581) [FullText HTML] (271) PDF 936KB(9)
Abstract:
To study the durability of concrete structure strengthened with CFRP(carbon fiber reinforced polymer) under hydrothermal environment, six concrete beams strengthened with CFRP under warm and moisture conditions were used for flexural behavior experiment; the failure mode, bearing capacity, deflection and crack were studied by the experiment. Based on differential equations of chemical reactions and exponential law of reaction rate for epoxy resin aging, the attenuation model of elastic modulus was given for epoxy resin under warm and moisture conditions. From the mechanical properties of concrete and epoxy resin, theoretical formula of CFRP peel strength was given for concrete beams strengthened with CFRP under hydrothermal environment, and the flexural capacity formula was also put forward. The results show that the flexural capacity of strengthened concrete beams decrease exposed to environmental conditions, and peeling failure of CFRP is gradually transferring from the interface region of concrete side to the interface region of CFRP side. As the environmental effect continues, the number of cracks and deflection reduce while the crack width increases, which show that both damage and brittleness of strengthened beam increases. The yield curvature, ultimate curvature and curvature ductility factor of the strengthened beam reduce, and it indicates that the ductility of the strengthened beam deteriorates, but the brittleness and dispersion of the CFRP peeling failure increase. The comparison between the experimental and theoretical analysis shows that the relative error of the theoretical and the experimental value is smaller than 20% for CFRP ultimate strain, and the relative error is smaller than 11% for flexural capacity.
Experimental Study on Seismic Behavior of Resilient Circular Concrete Columns
LIU Zhihua, ZHAO Hua, SUN Yuping, ZHAO Shichun, ZHAO Jun
2020, 55(1): 184-192. doi: 10.3969/j.issn.0258-2724.20180451
[Abstract](542) [FullText HTML] (197) PDF 1264KB(14)
Abstract:
In order to maintain the positive stiffness and small residual deformation of reinforced concrete columns when they are subjected to tremendous earthquakes that exceed the standard set by current codes, a method of using high-strength and low-bond non-prestressed steel strands as longitudinal reinforcement bars of columns is proposed. In order to verify the effectiveness of this method, horizontal low-frequency cyclic loading tests were performed on four circular reinforced concrete columns under a constant axial load, of which three were reinforced with the above-mentioned longitudinal steel strands (hereinafter referred to as ‘new type columns’) and one with normal-strength (NS) rebars. The effects of shear-span ratios and transverse confinement modes within the potential plastic hinge region on the seismic behavior of the new type columns were studied. The test results show that when the drift ratio of the new type columns with a shear-span ratio of 3 to 4 reaches 6%, it still maintains positive stiffness and the residual drift ratio is less than 2%. Compared with the concrete column reinforced with NS rebars, the lateral bearing capacity of the new type column was increased by 90% and the residual deformation was reduced by 73% at the drift ratio of 6%. Besides, the lateral bearing capacity of the new column can be further increased by 15% and the residual deformation can be further reduced by 21% by adding transverse confinement with bolted steel plates in the plastic hinge zone of the column (1.5D). Comparisons between the experimental and analytical results indicate that the flexural analysis based on Navier’s hypothesis is not suitable for prediction of the lateral bearing capacity of the concrete columns reinforced with steel strands due to the the obvious bond-slip effect of steel strands.
Effective Diffusion Range of Exponential Fluids Based on Navier-Stokes Equation in Collapse Area
WEN Lei, LUO Zhouquan, QIN Yaguang, WANG Wei, ZHENG Kaihuan
2020, 55(1): 193-201. doi: 10.3969/j.issn.0258-2724.20180331
[Abstract](485) [FullText HTML] (198) PDF 1971KB(21)
Abstract:
In order to study the diffusion range and pressure distribution of cement paste during grouting in the fractured rock mass, based on the deduced Navier-Stokes equation, a single fracture model is established on the COMSOL platform to simulate the flow characteristics of slurry on irregular single fracture surface. In this regard, a plane fracture model with different penetration coefficients is established to simulate the diffusion law of the slurry in the broken rock mass. The results show that when the crack penetration coefficient is low in the model (0.1−0.5), the effective diffusion range of the slurry is small, about 1.5−4.1 m, and the diffusion distance increases slowly and nonlinearly with the increase of pressure difference, and the increase rate decreases to near 0 quickly. When the fracture penetration coefficient in the model is larger (0.5−1.0), the effective diffusion range of the slurry increases significantly, about 4.1−6.2 m; and it increases nonlinearly with the increase of pressure difference, and the rate of increase decreases gradually. When the fracture penetration coefficient of the model is 1.0, the fractured surface of broken rock is all connected. The diffusion distance of slurry increases approximately linearly with the increase of pressure difference, and the maximum diffusion distance is about 6.2 m. Meanwhile, the results of coring at 6 m around the grouting hole show that the fractured rock mass consolidated by the slurry can be clearly observed, which is consistent with the calculation results of the model.
Study on Creep Test of In-situ Scaling Model of Suspension Bridge Tunnel Anchorage
WEN Lina, CHENG Qiangong, CHENG Qiang, GUO Xifeng
2020, 55(1): 202-209. doi: 10.3969/j.issn.0258-2724.20181013
[Abstract](533) [FullText HTML] (211) PDF 1362KB(6)
Abstract:
In order to obtain the creep deformation law of tunnel anchor of Luding Dadu River super-large suspension bridge on Yakang Expressway, creep test of 1∶10 in-situ scale model of tunnel anchor was carried out according to similarity theory. The graded loading test of model anchor was carried out with gas-liquid loading system, the creep process of model anchor, surrounding rock and interface dislocation under 1.00P (single design tension of scale model), 3.50P, and 7.00P loads were analyzed. The three-dimensional viscoelastic-plastic simulation analysis of creep of anchorage and surrounding rock mass was carried out by FLAC3D, and the simulation value was compared with the measured value. The results show that under 1.00P, 3.50P, and 7.00P loads, the maximum creep of anchor body are 0.62, 0.97 mm, and 1.58 mm, the maximum creep of surrounding rock are 0.49, 0.85, and 1.38 mm, and the maximum creep of anchor body and surrounding rock are 0.15, 0.64 mm, and 1.43 mm, respectively. The measured creep deformation of anchorage and surrounding rock is equivalent to the calculated value, and the creep trend is basically the same. The tunnel anchor and surrounding rock of Yakang super-large suspension bridge belong to stable creep under various loads, the creep of anchorage does not affect the long-term stability of suspension bridge under normal design loads.
Main Influencing Factors of Dust Removal Efficiency by Negative Ionization in Tunnel Construction
XU Shiqiang, WANG Mingshan, LI Jie, HU Yaozhou, REN Hongyuan
2020, 55(1): 210-217. doi: 10.3969/j.issn.0258-2724.20180367
[Abstract](557) [FullText HTML] (242) PDF 1079KB(14)
Abstract:
In order to study the influence of dust particle size, particle concentration, ventilation velocity, the working voltage of a negative ion system and its longitudinal installation position on the dust removal efficiency of the negative ion system in tunnel construction, a three-dimensional model of tunnel and negative ion system is established and the tunnel calculation parameters are selected according to investigation and measurement for numerical simulations. The RNG k-ε dual equation turbulence model is used to solve the current field by the momentum equation with electric field force source term. The trajectory of dust particles is solved by Lagrange method. The SIMPLE (semi-implicit method for pressure linked equations) algorithm is used to simulate the coupling between discrete and fluid phases of electric field, flow field and particle motion. In addition, field tests in the tunnel were carried out to verify the accuracy of the simulation results. The results show that the dust removal efficiency of the negative ion system improves with larger dust particle size, greater dust concentration, lower wind speed of the tunnel, higher working voltage of the negative ion system, and closer installation position of the system to the tunnel working face. Dust removal efficiencies of two groups of field sampling tests were 41.2% and 56.7% while the counterparts of numerical simulations were 38.2% and 51.1%, hence deviations being 15.5% and 12.9%, respectively. Therefore, considering the influence of large space and complex environment of tunnel under construction, it is feasible to study the dust removal efficiency of negative ion system and its relationship with main influencing factors by numerical simulation.
Parameters Quantification of Forchheimer Equation and Critical Point of Transition from Darcian to Non-Darcian Flow
LIU Jian, YANG Qiaoyan, BAI Xue, SONG Kai, LUO Chengjie, SA Yongfang
2020, 55(1): 218-224. doi: 10.3969/j.issn.0258-2724.20180756
[Abstract](540) [FullText HTML] (696) PDF 1200KB(73)
Abstract:
In order to explore the movement law of water flow in rock mass fissures, a fracture seepage flow model was established with real rock mass materials to study the seepage flow state and parameters. The single-fracture seepage flow model was constructed using natural marble blocks, instead of the common non-stone materials such as cement, glass, acrylic, and steel. Based on the model, seepage experiments with different fissure widths (0.77, 1.18, 1.97, 2.73 mm) were conducted to investigate the relationship between pressure loss and flow rate, the critical point of transition from Darcian to non-Darcian flow, and the quantification of parameters in the Forchheimer equation. Results show that the relationship between pressure gradient and flow rate is governed by linear Darcy’s law when the fracture width is 0.77 mm, but obvious non-Darcy characteristics are observed with the increase of the fracture width and flow rate, which can be described by Forchheimer equation. The coefficient of viscosity and inertia term of the Forchheimer equation can be expressed as a power function of fracture width, and the error can be reduced by introducing Reynolds number to correct the inertia coefficient. Besides, the method of judging the critical point of transition from Darcian to non-Darcian flow via the slope characteristics of pressure gradient-flow curve proved feasible in this experiment.
Biotransformation of Bioethanol from Lignocellulose by High Yield Cellulase-Producing Aspergillus
LIU Yang, QIU Zhongping, MENG Tao, GONG Zhengjun, WANG Dongmei, FAN Chao
2020, 55(1): 225-230. doi: 10.3969/j.issn.0258-2724.20180477
[Abstract](481) [FullText HTML] (206) PDF 591KB(15)
Abstract:
Biotransformation of bioethanol was innovatively processed with crude enzyme to hydrolyse rice straw from a high-yield cellulase-producing Aspergillus W-10 and by simultaneous saccharification and fermentation (SSF) with Saccharomyces cerevisiae. Hydrolysis and saccharification of pretreated rice straw by crude enzyme with cellulase and cellobiase was measured at regular sampling of reducing sugar. Meanwhile, the impacts of substrate concentration, the amount of surfactant and synergism of cellobiase on hydrolysis process were studied. Then, the effects of fermentation temperature, fermentation time and initial pH value on the SSF were also explored on the bassis of the optimized hydrolysis conditions. The results show that when the concentration of substrate was 80 g/L, the concentration of surfactant Tween-80 was 5 g/L, and the amount of cellobiase was 166.67 nkat/g, the highest efficiency of hydrolysis of crude enzyme was observed. When the fermentation temperature was 35℃, the fermentation time was 4 d, and the initial pH value was 5, the concentration of ethanol in fermentation broth was the highest, reaching 0.43 g/g (dry weight of substrate). The optimization of the reaction conditions of high yield cellulase-producing Aspergillus W-10 can promote the bioconversion technology development of lignocellulosic ethanol, which is beneficial to the large-scale commercial production and application of bioethanol as a renewable clean energy.

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