Table of Content

25 July 2019, Volume 47 Issue 7

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Architecture & Civil Engineering

Axial Compression Behavior of CFRP-confined Damaged Reinforced Concrete



LAO Xiaojie HAN Xiaolei JI Jing JIANG Zhengrong CHEN Binbin

2019, 47(7):  1-9.  doi:10.12141/j.issn.1000-565X.180645

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A total of 29 square reinforced concrete (RC) columns with different amounts of internal steel rein- forcement and of externally wrapped CFRP as well as pre-damage levels，were designed and tested under axial compression． On the basis of regression analysis of the test results，a stress-strain model for CFRP-confined da- maged reinforced concrete under axial compression was proposed． The test results show that CFRP wrapping is effec- tive in restoring or even enhancing the compressive strength and the strain capacity of damaged reinforced concrete． Both the compressive strength and the ultimate strain of CFRP-confined damaged reinforced concrete increase with the increase of the quantities of CFRP and the decrease of pre-damage levels，while the initial elastic modulus de- creases with the increase of pre-damage levels． Under cyclic loading，the envelope curve of cyclic stress-strain re- sponse of CFRP-confined damaged reinforced concrete under axial compression coincides with the monotonic coun- terpart． The prediction provided by the proposed model agrees well with the test results．

Influence of Monolithic Slab on the Actual Axial Force of Frame Beam in RC Frame Structure



WANG Suguo

2019, 47(7):  10-18.  doi:10.12141/j.issn.1000-565X.180021

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In cast-in-situ Reinforced Concrete (RC) frame structures，the strengthening effect of monolithic slab on the structural integrity makes actual axial force in frame beam cannot be ignored． The axial force distribution of frame beam along beam span in regular RC frame structures subjected to vertical and lateral loading were respec- tively detailedly analyzed． Moreover，the axial force distributions corresponding to different arrangement of mono- lithic slabs in RC frame structures were also studied and compared with each other． The research results show that: monolithic slab is the main reason of beam axial force uneven distribution in actual RC frames and the axial force presents as axial compression force at beam end with hogging moment which cannot be ignored during design stage; the influencing way of monolithic slab is to limit the axial deformation of beam and consequently generate beam axial force; monolithic slab mainly influence the frame beams which are directly connected with it，and almost has no influence on the frames beams which are not directly connected with it． Based on this，the causes and composi- tions of beam axial forces under the action of sagging and hogging moments were studied respectively． Then a de- sign recommendation considering the influence of monolithic slab on frame beam was proposed to improve the reali- zation effect of strong column weak beam．

Study on the Stability Bearing Capacity of Unequal Angle Cross Bracing of Ultra-high Voltage Transmission Tower



ZHANG Yi LI Zhengliang LIU Hongjun LIU Shuyu

2019, 47(7):  19-31.  doi:10.12141/j.issn.1000-565X.180488

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The mechanical properties of unequal angle cross bracing of ultra-high voltage (UHV) transmission tower were studied． Two full-scale internodes adopting unequal angle cross bracing，used commonly in UHV trans- mission tower in China，were made and carried on the static test under different working conditions． The strain de- velopment，the characteristics of deformation，the failure mode and the ultimate bearing capacity of the unequal angle cross bracing were mainly studied; then the nonlinear finite element analytical (FEA) model of internodes were established and verified by test． The parameters of FEA model of internodes were analyzed． The test results show that the bearing capacity of unequal angle cross bracing is good in different working conditions loading，when the load reaches the limit value，the failure mode of the unequal angle cross bracing was determined by loading mode to be out-of-plane buckling or out-of-plane and in-plane buckling． The parameter analysis shows that the bearing capacity of cross bracing is improved with the decrease of the internal force ratio，the increase of material strength and the increase of the intersection position． The improvement of bearing capacity of cross bracing is sig- nificantly affected by loading mode． Finally，based on the energy method and the finite element method，the theo- retical method of bearing capacity of unequal angle cross bracing were provided． It turns out that the theoretical re- sults are in good agreement with the results of test and FEA．

Architectural Planar Quadrilateral Grid Generation for Free-form Surfaces Based on Spring-mass Model



GAO Boqing LI Zheng WU Hui

2019, 47(7):  32-39.  doi:10.12141/j.issn.1000-565X.180438

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In order to obtain the planar quadrangle architectural mesh of free-form surfaces，a mesh optimization algorithm based on mechanical simulation was proposed． The spring-mass model comprised of restraint force for rod length，the restraint force for boundary fixed particle，the adsorption force for surface to particle and the force for mesh planarization，was established． First，according to the designer，mapping method or other methods were used for the initial quadrangle grid generation． Then，considering the requirements of different performance，the elastic coefficient k ij ，boundary constraint stiffness k c ，adsorption stiffness k m ，and planarity coefficient p c were calculated． The mesh spring particle model with coplanar target was established，and the coplanar mesh was ob- tained by multiple iterations through dynamic relaxation method． Then，combined with the quadrilateral planariza- tion index，the quality of the grid was evaluated comprehensively by fluency index and uniformity index，and the grid deviation index was introduced to control the shape of the grid． Finally，examples were given to verify the re- sults． Examples show that the planarity optimization algorithm can be well adapted to free-form surfaces． By adjus- ting the parameters，the allowable error limits of planarization can reach a reasonable range with fluent and uniform architectural grids under certain conditions．

Novel Mechanisms of Structural Optimization Based on Plant Growth Simulation Algorithm



SHI Kairong PAN Wenzhi JIANG Zhengrong LUO Bin

2019, 47(7):  40-48,57.  doi:10.12141/j.issn.1000-565X.180571

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As a new heuristic intelligent optimization algorithm，plant growth simulation algorithm (PGSA) esta- blishes the dynamic growth model based on the plant phototropism mechanism and forms the search mechanism rapid- ly towards the global optimal solution． According to the characteristics of large-scale complex optimization problems such as large growth space，multiple design variables，multiple local optimal solutions，difficulty in automatic ter- mination and so on，three novel improved mechanisms (the limited strategy of growth point set，the elimination strategy of new growth points，the parallel search strategy of mixed step size) were proposed based on the basic principle of PGSA and the effectiveness of the proposed improved mechanisms were proved by typical mathematic example and structural example of truss． Several conclusions can be drawn: (1) the scale of growth space can be effectively controlled by the limited strategy of growth point set，which leads to high search capacity of the algo- rithm; (2) combined with the former strategy，the elimination strategy of new growth points can provide effective termination mechanism for PGSA; (3) excellent global search capacity can be offered by the parallel search strate- gy of mixed step size in the early growth stage and the optimal solution range can be quickly obtained． The pro- posed mechanisms can dramatically improve the effectiveness and adaptability of PGSA in optimization，which pro- vides a new approach for structural optimization problems．

Automatic Updating Method of Finite Element Model and Its Application Based on Ambient Vibration and Bayesian Theorem



LIU Pei ZHU Haixin LIAN Pengyu YANG Weiguo

2019, 47(7):  49-57.  doi:10.12141/j.issn.1000-565X.180429

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The effects of uncertainties due to test and model errors on the updated model parameters are not consi- dered in the traditional finite element model updating methods． These methods are difficult to be applied to compli- cated structures． To solve the above problems，a Bayesian finite element model updating method based on ambient vibration test and interactive access of commercial software was proposed． Modal parameters were identified by a fast Bayesian FFT method with the ambient vibration test data． Taking the identified modal parameters as known data，the posterior probability density function of the updated parameters was obtained by Bayesian theorem． By minimizing the negative log-likelihood function with the simplex method，the most probable values and coefficients of variation of the updated parameters were obtained． A data-exchange algorithm was employed to integrate the Bayesian structural model updating method in MATLAB with the finite element analysis results in SAP2000 to up- date the finite element model parameters automatically． Ambient vibration tests and modal parameter identification were conducted on two long-span floor structures． The proposed method is employed to update the values of elastic modulus of concrete floors and steel beams． The modal analysis results from the updated finite element model agree well with the identified ones．

Impact of Passive Energy-saving Technology on Ecology of Lingnan High-rise Residential Buildings



LUO Jianhe SHI Gang QIN Siyuan DING Yi

2019, 47(7):  58-67.  doi:10.12141/j.issn.1000-565X.180025

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Passive energy-saving method helps buildings exchange energy with the surrounding environment without mechanical power based on their climate characteristics． These methods can reduce the energy consumption of buildings and improve architectural ecology． Taking“Hengqin New Home”as an example，the simulation results of buildings' physical environment simulation calculation software were compared with the actual measured results of various physical indicators． It aims to study the application of passive energy-saving technology in high-rise resi- dential buildings，and its impact on the ecology of high-rise residential buildings in south of five ridge of China (also referred“Lingnan area”)． The study shows that high-rise residential buildings in Lingnan area should take measures to reduce solar radiation and strengthen indoor natural ventilation in order to improve indoor environmental comfort． In order to maintain comfortable indoor ventilation effect，the main orientation of buildings should be as far as possible to face the dominant wind direction，and ensure smooth and uniform indoor ventilation channels． Besides，the open area of natural ventilation should meet the requirements and the device should be adjusted con- veniently so that residents can open it flexibly． There is a large cooling demand and new air demand for high-rise residential buildings in Lingnan area throughout the year，so，it is necessary to make rational use of the building shading components to reduce the solar radiation heat gain，and to introduce outdoor fresh air into the indoor cool- ing and supplement the indoor the indoor fresh air in the suitable state，so as to realize the energy and material ex- change between the building and surrounding environment，and to create a harmonious building environment with heat generation eco-system and wind eco-system．

Traffic & Transportation Engineering

Research Development of Superconducting Maglev Transportation



MA Guangtong YANG Wenjiao WANG Zhitao YE Changqing LI Jing

2019, 47(7):  68-74,82.  doi:10.12141/j.issn.1000-565X.180423

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With the merits of safety，economic，environment-friendliness，magnetic levitation (maglev) vehicle is the typical represent of advanced type of rail transit． High temperature superconducting (HTS) maglev vehicle which is based on the flux-pinning effect，and electrodynamic suspension (EDS) maglev vehicle which takes su- perconducting magnet as on-vehicle active cell are the main forms of superconducting maglev traffic． The structure， theory and development of two kinds of superconducting maglev vehicles were introduced，and their advantages and disadvantages were analyzed． On the basis of“high speed”developmental direction of maglev transportation，vac- uum tube HTS maglev and EDS maglev with HTS magnet instead of low temperature superconducting magnet will be the main trends for future high-speed transportation．

Effect Evaluation of Multiple Recycled SBS Modified Asphalt Based on Viscoelastic Properties#br#



ZOU Guilian QIN Huan YAN Ran SUN Jie

2019, 47(7):  75-82.  doi:10.12141/j.issn.1000-565X.180525

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The dynamic mechanical analysis (DMA) method was adopted to study the viscoelastic properties of multiple recycled SBS modified bitumen． The recycling effect and the retention degree of unique viscoelasticity of SBS modified asphalt were evaluated by comparing the parameters such as complex modulus，phase angle，the va- riation of rutting factors，elastic recovery rate and unrecoverable creep compliance． The aging and regeneration processes were observed by fluorescence microscope． The results show that recycling effect of SBS modified asphalt is getting worse and the unique viscoelasticity of SBS modified asphalt is decreasing gradually with the increased times of asphalt aging and recycling． Multiple stress repeated creep (MSRC) tests show that the repeated recycled asphalt is more sensitive to the stress level，and the elastic recovery ability becomes worse and closer to the hard asphalt． Therefore，it is difficult to meet the MSCR classification standard suitable for SBS modified asphalt． Flu- orescence microscope was used to observe the aging and regeneration process． The images show that the SBS is poly- merized gradually during the aging process，and the compatibility become worse． The rejuvenating agent could on- ly supplement the decrease of the light component caused by the migration of the asphalt component during the aging process． However，the SBS modifier can't be redispersed． If SBS modified asphalt has been regenerated three times or more，and only rejuvenating agent can be used，then the recycled SBS modified asphalt can be used as hard asphalt． In oder to keep good road performance of modified asphalt pavement，the newly added modified asphalt should supplement old asphalt's loss of SBS viscoelastic characteristics． So customizing new modified as- phalt will become a technical approach．

Study on Degradation of Tunnel Exhaust Gas Based on Composite Nano Photocatalytic Materials



GUO Yinchuan XIE Zhiteng SHEN Aiqin ZHANG Youhua

2019, 47(7):  83-89.  doi:10.12141/j.issn.1000-565X.180291

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The composite photocatalytic material TiO₂ -CeO₂   was incorporated to steel slag asphalt mixture in tunnel environment in order to study its efficiency for exhaust gas degradation． Firstly，a complete set of tail gas degrada- tion test equipment capable of simulating tunnel environment was developed． Then the influence of composite pho- tocatalytic material TiO₂ -CeO₂    on the performance of steel slag asphalt mixture in asphalt pavement was studied． Finally，the optimum doping ratio of TiO₂ -CeO₂   composite photocatalytic material was also studied． The results show that when the nano-TiO₂ volume is 50% and nano-CeO₂ is 0. 7%，the photocatalytic efficiency will reach to the peak value． In this case，the degradation efficiency peak of NO and HC is 89% and 95%，respectively，and exhaust degradation efficiency reach up to 626. 3 mg/ (m³ ·min) and 74. 75 mg/ (m³ ·min) within 30 min，re- spectively． The road performance of tunnel steel slag asphalt mixture meets the requirements．

Reliability of Subway Bogies Based on Probability Cumulative Damage and Wiener Process



ZHANG Zifan LI Qiang LI Xiang ZHANG Chaojie

2019, 47(7):  90-98.  doi:10.12141/j.issn.1000-565X.180506

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A method for studying fatigue reliability variation of urban rail vehicle frame based on measured stress data was put forward． In order to establish the relationship between structural damage and reliability，firstly，a new heuristic algorithm was used to fit the probability density function of the stress spectrum for each day． And a probabilistic cumulative damage model considering load interaction was derived based on the statistical distribution of stress． Then，considering the difference of the results of different sensors in a certain structure area，the gene- ral variation law of structural reliability with operational mileage was obtained by using Wiener process with random effect based on Probabilistic Damage statistics and Markov chain-Monte Carlo method． The calculation results show that the reliability calculation method can obtain the fatigue reliability results of the frame which are consistent with the engineering experience．

Incorporating the Heterogeneity into Travelers' Green Traveling Choice Model



LIU Jianrong HAO Xiaoni

2019, 47(7):  99-104,120.  doi:10.12141/j.issn.1000-565X.180365

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Restricting privates car use and promoting pure electric vehicles use are two important ways to realize green travel in China cities． In order to analyze the impact of travelers' environmental awareness on green travel， travelers were categorized with the latent class analysis based on travelers' attitude towards environment and trave- ling behaviors． Then travelers' latent class was introduced into the traditional bi-variate probit model as explanatory independent variables． And the impact of travelers' latent class on the approval of private car restriction policies and the purchase intention of pure electric vehicles were analyzed． The results show that according to their attitude towards environment and traveling behaviors，travelers can be categorized into three latent classes: the environ- mentalist，the non-environmentalist，the pseudo-environmentalist． There is a higher degree of fitting when incor- porating travelers' latent class into the bivariate probit model． And travelers' latent classes have great impacts on their green traveling choice．

Low Carbon Travel Intention Data Mining for Residents Based on K-means Clustering and Random Forest Algorithm



WU Wenjing JING Peng JIA Hongfei ZHANG Minghang

2019, 47(7):  105-111.  doi:10.12141/j.issn.1000-565X.180116

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The research on the formation mechanism of residents' low carbon awareness will provide important basis for traffic managers to guide urban residents to choose low carbon travel． The questionnaire survey data of low car- bon travel intention were analyzed． The 15-dimensional questions under the framework of the theory of planned be- havior were considered as the intrinsic variables for residents' low carbon travel intention． K-means clustering algo- rithm was used to classify individual types according to individuals' willingness intensity． The results were used as the explanatory variables in the random forest algorithm for identifying individuals’attribute characteristics and travel characteristics of different types of individuals． The results show that，based on the Silhouette index test and the t-SNE dimension reduction visualization，the residents' low carbon travel intention can be divided into three categories: willingness，neutrality and unwilling; and based on the importance of the indicators，the 4 most signi- ficant factors are identified as the individual's occupation，residence，family composition，travel time． The re- search results provide suggestions for the development and management of urban traffic low carbonization from multi- ple perspectives．

Mechanical Engineering

Energy Management Strategy for a Power-split Hybrid Electric Vehicle Based on Explicit Stochastic Model Predictive Control



QIN Datong QIN Ling

2019, 47(7):  112-120.  doi:10.12141/j.issn.1000-565X.180590

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Energy management strategies are important for hybrid electric vehicles to improve fuel economy． In or- der to improve the fuel economy of power split hybrid vehicles and the real-time performance of energy management strategies，an energy management strategy based on explicit stochastic model predictive control was designed． Firstly，the Markov chain was used to predict the vehicle speed． Then by simplifying the control model and trans- forming the nonlinear energy management problem into a linear quadratic optimization problem，a stochastic model prediction strategy (SMPC) with the minimum energy consumption in the prediction domain was established． Sec- ondly，the explicit stochastic model prediction strategy is obtained by solving the problem parametrically，and this strategy not only maintained the advantages of the stochastic model predictive control method，but also improved the calculation speed． Finally，the simulation is carried out under multiple working conditions to verify the effec- tiveness of the proposed energy management strategy． The simulation results show that fuel economy can be in- creased by up to 28. 64% compared to rule-based control strategies，and the average calculation time in the simu- lation is 3. 1ms，which indicate that the strategy has real-time computing potential．

Numerical Analysis of Material Fracture Splitting Performance of Rear Axle's Main Reducer Shell Bearing Seat



KOU Shuqing XIU Tingting JIN Wenming ZHAO Yong YAO Juan

2019, 47(7):  121-127,135.  doi:10.12141/j.issn.1000-565X.180495

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The microstructure of rear axle main reducer shell bearing seat material QT450 with 25% P + 75% F and 50% P + 50% F was compared to study the internal relation between structure and fracture splitting perfor- mance． Firstly，tensile tests were performed on the QT450 specimens with different metallographic structure to ob- tain the material parameters required for numerical simulation． Combined with the simulation，the critical fracture toughness J IC of the two matrix tissues was determined respectively． The fracture-splitting force and the stress con- centration of QT450 with different microstructures were obtained by ABAQUS． Then a springback model was estab- lished to analyze the plastic deformation and out-of-roundness of the two tissues． Finally，the fracture splitting test was carried out to verify the validity of the numerical analysis． The results show that QT450 with 50% pearlite + 50% ferrite is more suitable for the fracture splitting than QT450 with 25% pearlite + 75% ferrite． The strength and stiffness of QT450 material depend on the content of pearlite． With the increase of pearlite content，the britt- leness of the material，the notch sensitivity increase and the fracture splitting performance are all improved． The shell bearing seat produced by QT450 with 25% pearlite + 75% ferrite matrix has an out-of-roundness of more than 0. 2 mm，which can not complete the subsequent finishing and assembly． While the shell bearing seat pro- duced by QT450 material with 50% pearlite + 50% ferrite has an out-of-roundness of less than 0. 2 mm，and the plastic deformation caused by fracture splitting is small，so it can well meet the requirement of the actual produc- tion process．

Optimization of Engine Cooling Fan Tip Parameters



WAN Lixiang DUAN Lina GUO Qin DUAN Yaolong YU Ning SHANGGUAN Wenbin

2019, 47(7):  128-135.  doi:10.12141/j.issn.1000-565X.180065

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The engine cooling fan is an important part of the vehicle cooling system． Static pressure and shaft po- wer are important indicators to evaluate its aerodynamic performance，and the tip of the blade as a main part of the fan work has a great influence on the aerodynamic performance of the fan． Taking the cooling fan of the engine as the research object，the calculation method of aerodynamic performance of the fan and the optimization method of blade tip parameters were studied． Firstly，the calculation method of fan aerodynamic performance was given，and the fan calculation model was established according to the test bench． Then a new fan was designed with the tip mounting angle，the tip length and the tip arch height as the variables． Based on the orthogonal test method，the parameters of the blade tip parameters were optimized and combined，and the optimization method of the fan tip pa- rameters was given． Finally，the optimization results were further analyzed from fan performance curve，blade pressure diagram and blade velocity vector diagram，and the feasibility of the optimization method was verified． This analysis and optimization method of fan tip parameters is of guiding significance for the design of engine cooling fan．

Improved Contact Searching Algorithm of Large Step Implicit FEMs



LIU Yongcai BAO Yidong HU Qingwan CHEN Wenliang

2019, 47(7):  136-144.  doi:10.12141/j.issn.1000-565X.180371

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The large step implicit FEMs have been widely used in the field of sheet metal forming due to its fast calculation speed and highly accuracy． Many historical contact information may be changed for the current time step in implicit FEMs which makes the contact searching problem more difficult，and a robust contact searching al- gorithm is necessary． Combining location code algorithm and Alternating Ditigal Tree (ADT) structure，an algo- rithm based on master-slave method was proposed for large step implicit FEMs，and it was integrated into the QuickForm software． The experimental results show that the algorithm has good search performance． For many complex forming parts，the average search efficiency is up to about 20%．