Table of Content

25 September 2020, Volume 48 Issue 9

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Architecture & Civil Engineering

Improvement of HAM-Model Based on Capillary Pressure Logarithm



MENG Qinglin LI Fuxiang LI Qiong

2020, 48(9):  1-9.  doi:10.12141/j.issn.1000-565X.190881

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In response to the extremely hot-humid weather in the South China Sea area，a novel 1-D transient heat and moisture coupled transfer model (LPc-model) for building walls was developed by selecting capillary pressure logarithm as the moisture driving potential and the outdoor and indoor air parameters as the boundary conditions and taking the air infiltration into account． HAMSTAD Benchmark 2，3 were used to verify the accuracy of the model．The good agreements between the calculated results and benchmark test results indicate that the model can be used to calculate the heat and moisture coupled transfer including air infiltration inside the wall． The applicability，accu-racy，and calculation efficiency of the new model was compared with the existing capillary pressure model (Pc-mo-del) and relative humidity model (ＲH-model) under benchmark test condition and a realistic condition． The results show that only the LPc-model and ＲH-model can calculate the two benchmark tests accurately，LPc-model has the fastest convergence speed，and Pc-model cannot completely calculate the benchmark 3． Under real weather conditions，only LPc-model and ＲH-model can complete the calculation，and ＲH-model has a faster convergence speed and more narrower fluctuation in the results．


Analysis of Monitoring Data of a Long-Span Steel Roof Based on BIM and BP Neural Network



YANG Chun, LI Penglin, XIONG Shuai, et al

2020, 48(9):  10-19.  doi:10.12141/j.issn.1000-565X.190902

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Temperature and strain measured data of the steel grid roof structure at Zhuhai port of Hong Kong-Zhu-hai-Macao bridge were taken as the actual engineering background，and the nonlinear relationship between tempera-ture and strain was simulated by back propagation (BP) neural network to realize temperature effect prediction of long-span spatial steel structure． The strain monitored of the structure under the action of temperature load and wind load was separated to realize the independent determination of the dominant working condition of the loads of the member． Finally，a neural network program based on database and Matlab interface was developed，and it was fur-ther embedded into building information model (BIM) software in the form of a plug-in． The information obtained from the analysis of the monitoring data was integrated into the BIM three-dimensional model，so as to guide the monitoring personnel to conduct maintenance on the structure． The neural network model constructed in this study can well fit the non-linear relationship between temperature and strain of long-span spatial steel structure． Based on the secondary development of BIM technology，the prediction of temperature effect and the identification of wind load were realized，and the research on the analysis of monitoring data was further developed，which can provide reference for similar projects．


Interface Bond Behavior of High Strength Concrete Filled Square Steel Tube Subjected to High Temperature and Subsequent Water Cooling



CHEN Zongping, ZHOU Ji, CHEN Jianjia, et al

2020, 48(9):  20-33.  doi:10.12141/j.issn.1000-565X.190904

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To study the interface bond behavior of high strength concrete filled square steel tube (HSST) subjected to high temperature and subsequent water cooling，22 specimens were designed to carry out static push-out tests in-cluding 18 water cooling specimens and 4 natural cooling specimens，and the effects of concrete strength，maximum temperature，anchorage length，constant temperature and cooling mode were mainly considered． The interface fai-lure mechanism of the HSST subjected to high temperature and subsequent water cooling was revealed through ex-periments，and the influence of various parameters on the bond properties was analyzed． In addition，the formulas for calculating ultimate bond strength and residual bond strength of HSST subjected to high temperature and subse-quent water cooling were put forward． The results show that the load-slip curves of the loading end and the free end of the specimen subjected to high temperature and subsequent water cooling can be divided into two kinds of typical curves． After high temperature and subsequent water cooling，the bond strength of the specimen increases first and then decreases with the increase of the maximum temperature，increases with the increase of the concrete strength，and decreases with the increase of the anchor length． Compared with that at holding time for 60 min，the bond strength of the specimen at holding time for 90 min rebounds． Compared with the natural cooling specimens，the ul-timate bond strength，residual bond strength and bond shear stiffness of the specimens subjected to water cooling are smaller，and the interface energy dissipation capacity is larger． The results calculated by the calculation formula of the bond strength proposed agrees well with the experimental results．


Compressive Performance of Brick Columns Strengthened with Textile Reinforced Concrete



TIAN Wenling, LI Xinbo, ZHOU Jian, et al

2020, 48(9):  34-42,70.  doi:10.12141/j.issn.1000-565X.190912

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To investigate the compressive performance of brick columns strengthened with textile reinforced con-crete (TRC)，12 brick columns were tested under axial compression and 8 brick columns were tested under eccen-tric compression． The influence of the number of textile layers，polyvinyl alcohol (PVA) fiber content and eccen-tric distance on strengthening effects were investigated． The results show that TＲC can significantly improve the bearing capacity，deformability as well as ductility of brick columns． The bearing capacity of brick columns increa-ses with increasing number of textile layers，but the relative increase rate of bearing capacity shows a downward trend when the number of layers exceeds 2． The strengthening effect of TRC can be further enhanced by adding PVA fiber into the TRC substrate，and the cracking loads and ultimate loads of strengthened columns are improved．The strengthening effect is better when the volume fraction of PVA fiber is about 0. 5%． The eccentric distance has a weakening effect on the hoop restraining action of TRC，and the strengthening effect gradually decreases with the increase of the eccentric distance． Based on the test results，a calculation method for the axial bearing capacity of brick columns strengthened with TＲC was proposed，and the calculation results agree well with the test results．


Experimental Study on Geopolymer Grouting Material in Rapid Grouting Reinforcement of Fractured Rock



FENG Han, ZHANG Xuemin, OU Xuefeng, et al

2020, 48(9):  43-50.  doi:10.12141/j.issn.1000-565X.190907

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Geopolymer material itself has the advantages of fast setting and high early strength． In order to further explore the early ( ＜ 24h) performance characteristics of the material and the possibility to apply it in the rapid grouting reinforcement of broken rock mass，the early ( ＜ 24h) mechanical properties and the working performance indicators of geopolymer grouting material，such as fluidity，initial / final setting time and water evolution rate，were studied through the orthogonal test，taking the modified water glass solution as the activator，and the metakao-lin mixed with slag as the precursor． The test results show that，compared with the traditional pure cement slurry，the geopolymer grouting material has the advantages of fast setting time，high fluidity，good stability and early high strength of the stone． It can be applied to some rapid grouting and strengthening conditions． When the replacement rate of mineral powder is 45%，the modulus and concentration of the modified water glass activator are 1. 5 and 75% respectively，and the liquid-solid ratio is 1. 5，the comprehensive performance of geopolymer is the best． The replacement rate of mineral powder and the concentration of modified water glass activator are the two main factors that have relatively large influence on the slurry．


Mechanical Engineering

Decision-Making Model and Algorithm for the Equipment Maintenance Strategy Under the Centralized Management in Business Park Areas



REN Yuan MA Zhiliang XIANG Xinglei

2020, 48(9):  51-60.  doi:10.12141/j.issn.1000-565X.190846

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It is difficult for business park area owners who manage multiple facilities centrally to coordinate with employed maintenance organizations to make maintenance decisions optimal for the entire business park area． This study，based on the results of previous studies，refines the problem of decision-making of equipment maintenance strategies under the centralized management as a knapsack problem and establishes the mathematical model． Then，an algorithm is selected and necessary improvement is made on the algorithm for solving the problem． A case with actual background validates the model and the algorithm． The results show that business park areas under the cen-tralized management can use the solution to make better equipment maintenance decisions than empirical methods scientifically and quantitively to avoid the most failure loss．


Reasoning Model for Mechanical Product Scheme Design Based on Extensional Ontology Related Network



WANG Tichun HUA Yang QIN Jiaqi

2020, 48(9):  61-70.  doi:10.12141/j.issn.1000-565X.190805

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An extensional reasoning model for complex product scheme design based on extension ontology correla-tion related network was put forward to solve the extension reasoning issue of relevant constraints in complex pro-duct scheme design． Firstly，an extensional ontology model for complex product scheme design was constructed，and the relativity of extensional ontology was analyzed． Secondly，the direction of product scheme design was obtained through domain knowledge，and the extension correlation function of extension ontology features was pro-posed． The extensional ontology correlation network was constructed based on the information model． Then，an extension reasoning algorithm for scheme design based on extensional ontology related network was presented． The initial product design scheme meeting design requirements was obtained through multi-level grey relational cluste-ring analysis of design direction and relational degree calculation analysis based on extensional ontology related net-works． Finally，the models and the algorithms were illustrated and validated by a design case of hydro turbine． The results show that the models and the algorithms are effective and feasible．


Pressure Characteristic Prediction and Analysis of Deflector Jet Servo Valve Jet-Pan Components



LI Shuanglu, YIN Yaobao, LIU Minxin, et al

2020, 48(9):  71-78.  doi:10.12141/j.issn.1000-565X.190867

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For the asymmetry and poor consistency of recovery pressures in the two receiving cavities of deflector jet servo valve，flow field simulation model considering the size and shape error of the jet-pan was established and the relationship between the shape factors of the jet-pan and the pressure characteristics was studied by using multi-ple linear regression analysis． The neural network algorithm was used to predict the recovery pressure of jet-pan components under different size and shape error combinations，and the shape factors distribution which cause the pressure difference excess was studied as well． Ｒesearch shows that the main factors affecting the recovery pressure include the width of wedge，the width of jet orifice，the thickness of jet-pan，the round corners of receiving cavities and the symmetry of wedge． And the main factors of the pressure difference between the two cavities are the symme-try of the wedge，the verticality of the jet orifice，the symmetry of round corners and the inner angle of the receiving cavities． The pressure difference between the two cavities is in normal distribution． The pressure difference excess is caused by the combination of several factors，but even if all the shape factors meet the design requirements，the pressure difference excess may occur． Experimental results agree with the theoretical results．



Thermal Performance Characterization of Hydrostatic Thrust Bearing Under High Speed and Heavy Load Working Conditions



YU Xiaodong, GAO Weicheng, WU Guangpeng, et al

2020, 48(9):  79-85.  doi:10.12141/j.issn.1000-565X.190774

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Due to the dual effects of strong shear and strong extrusion，oil-film has a large heat generation and the uneven rise of temperature leads to thermal deformation in the hydrostatic thrust bearing under high speed heavy load working conditions． The convective heat transfer of hydrostatic thrust bearing under different conditions is dif-ferent，which further causes uneven thermal deformation of the worktable and the base． In order to characterize its thermal characteristics，an equal-area segmentation method was proposed to calculate the convective heat transfer coefficient of hydrostatic thrust bearing under different conditions． The temperature distribution and thermal defor-mation of the workbench and the base was simulated by using ANSYS Workbench，and the thermal deformation dis-tribution and influence of load and rotational speed on their deformation were obtained and were verified by the built experimental setup． The results show that when the load is 0 ～8t，the deformation increases with the increase of the load and the decrease of the rotational speed; when the load is 8 ～24t，the deformation gradually decreases as the load increases and the speed decreases; when the load is 24 ～32t，the rotary table is Z negative deformation，and the maximum deformation is at the edge of the table． The maximum deformation of the base is concentrated on the lowermost rib part of the base． The deformation of the base is smaller than that of the rotary table． The deformation of the hydrostatic rotary table decreases when the load is 16 ～30t，and the optimal load is 16 ～30 t． It is recom-mended to further improve the thermal deformation resistance by optimizing its internal structure or enhancing heat dissipation．


Traffic & Transportation Engineering

Path Planning and Tracking Control for Emergency Lane Change and Obstacle Avoidance of Vehicles



ZHANG Jiaxu, YANG Xiong, SHI Zhengtang, et al

2020, 48(9):  86-93,106.  doi:10.12141/j.issn.1000-565X.200035

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An efficient path planning algorithm based on B-spline curve and a high-precision path tracking control strategy based on model predictive control method for emergency lane change and obstacle avoidance of vehicles were proposed，aiming at the problem of path planning and tracking control for emergency lane change and obstacle avoidance． Firstly，the B-spline curve-based differential flat output parameterization method was used to transform the problem of path planning for emergency lane change and obstacle avoidance of vehicles into the nonlinear pro-gramming problem of the control points of B-spline curve，and the interior point method was used to solve the non-linear programming problem to obtain the optimal path for emergency lane change and obstacle avoidance of vehi-cles． To execute the optimal path，a linear prediction model was established based on vehicle kinematics and dy-namics model，and a path tracking control strategy for emergency lane change and obstacle avoidance of vehicles，which can effectively deal with the constraints of the front wheel steering angle and the front wheel steering angle speed，was derived based on model predictive control method． Finally，the feasibility and effectiveness of the pro-posed path planning algorithm and path tracking control strategy for emergency lane change and obstacle avoidance of vehicles were verified by the vehicle dynamics software，and the simulation results show that the proposed method can guide the vehicle to avoid the obstacle safely，quickly and stably．


Biomechanical Model of Human Lumbar Spine and Sensitivity Analysis of Injury Parameters



TANG Liang, ZHENG Jiajia, LI Wenxi, et al

2020, 48(9):  94-106.  doi:10.12141/j.issn.1000-565X.190441

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With the rapid development of automobile industry，recent new cars are equiped with advanced passen-ger restraint system，which can better protect the occupants． However，the rate of thoracolumbar fractures is in-creasing year by year after the new car encounters frontal impact． Based on the geometry of GHBMC lumbar verte-brae model，a finite element model of human lumbar vertebrae with more accurate ligament parameters was estab-lished． By processing the experimental data of published papers，the tensile load curves of various ligaments and the corresponding load tensile curves under different loading rates were obtained，and the effects of the different pa-rameters of ligaments (ligament stiffness，failure zone，relaxation zone，the effect of strain rate) on lumbar spine injury was studied． A finite element model of lumbar spine with different curvature was constructed to study the effect of curvature on lumbar injury． Ｒesults show that ligament parameters and lumbar spine curvature has a great effect on lumbar spine response: the lower the stiffness of lumbar ligaments，the higher the risk of lumbar vertebrae injury; after considering the relaxation and failure areas of ligaments，the risk of lumbar vertebrae injury increases;considering the strain rate response of ligament load curve under high impact speed，the higher the impact speed，the higher the risk of lumbar vertebrae injury． At the same time，the vertical lumbar vertebrae has higher risk of lum-bar spinal injury than the bending lumbar vertebrae． The results are conducive to the design of occupant protection．


Effect of the Tunnel Warning System on Traffic Capacity Based on Aggregated Spatiotemporal Characteristics of Vehicles



CHANG Xin, LI Haijian, RONG Jian, et al

2020, 48(9):  107-115,123.  doi:10.12141/j.issn.1000-565X.200080

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To explore spatiotemporal characteristics of vehicles in a long tunnel road under the vehicle-road coopera-tive environment，the human-machine interface of tunnel warning system based on the connected vehicle technology was designed and a driving simulation experiment was carried out． 35 drivers' spatiotemporal characteristics of vehi-cle were studied by taking the group without warning system as the control group． The results reveal that when the system was on，the slowdown trigger points of vehicle was earlier，and the curvature values and number of inflection points of the spatiotemporal graph decreased． Moreover，the coefficient of variation of vehicle speed near the entrance and inside tunnel and the degree of overspeed in tunnel decreased obviously when the system was on． In conclusion，with the warning system，the driving pattern was changed from a visual stimulation-based response be-havior to a psychological expectation-based proactive behavior，which was easy to form the stable spatiotemporal characteristics． Further research shows that，assuming that the minimum headway of the following distance is 1. 5s，and based on the best converging patterns from 35 drivers' spatiotemporal trajectories，the overall traffic capacity was 21. 27% higher than that without the warning system．


Evaluation on Performance of Asphalt Pavement Based on Support Vector Machine



ZHAO Jing, WANG Xuancang, FAN Zhenyang, et al

2020, 48(9):  116-123.  doi:10.12141/j.issn.1000-565X.190841

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Focusing on the shortcomings of traditional models，a pavement performance evaluation model based on support vector machine (SVM) was proposed to comprehensively evaluate the performance of asphalt pavement．The method to determine the asphalt pavement performance training set and training labels was also proposed． At the same time，three optimization models，namely cross-validation (CV)，particle swarm optimization (PSO)，and genetic algorithm (GA)，were used to optimize the penalty parameter C and the kernel function parameter g which have effects on the accuracy of models，and their accuracy rate can reach to 99. 60%，96. 67%，94. 77% respec-tively． The results show that the best parameters obtained by cross-validation optimization have the highest accura-cy． Finally，taking the 23 maintenance sections of Guangyun Expressway as an example，the support vector ma-chine model and Technical Evaluation Standard for Highway Technology are respectively used to evaluate compre-hensive performance of the pavement． The results show that the model proposed in this paper is more suitable for practical application．


Impact of Increasing Load of Heavy Haul Train on Structural Response of Simply Supported T-shape Beam Bridge



XIAO Ye LUO Xiaoyong

2020, 48(9):  124-132.  doi:10.12141/j.issn.1000-565X.190868

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Taking the prestressed concrete simple T-shape beam bridge with common span of 16，20，24 and 32m as an example，the 3-D finite element model of the coupled heavy haul train-track-bridge system was constructed to study the impact of increasing load of heavy haul train on the structural response of prestressed concrete simple T-shape beam bridges in existing railways． The accuracy of model was verified by a case study of a typical pre-stressed concrete simple T-shape beam bridge in Shuo-Huang railway． The dynamic response of the train-bridge system under heavy haul train was calculated，the influencing rule of increasing load of heavy haul train on the dynamic responses of railway bridge structure was discussed． And the adaptability of increasing load of heavy haul train in typical bridges of the existing railways was also analyzed． The results show that when using the same kinds of freight trains，the displacement responses of the each span bridge increase linearly as the axle load of freight train increase，and the acceleration responses increases with the increase in the axle load of freight train． When using different kinds of freight trains，the dynamic responses of each span bridge fluctuated with the increase of the axle load，and the relationship between its change and the increase of axle load is not obvious． The length of train body and vehicle distance have a big influence on long-span bridges． When the span is small (less than 8m)，the dy-namic response of the heavy haul train to the bridge is only concerned with the wheelbase． When the train axle is lifted to 30t and above，the lateral dynamic response of typical railway bridges is rather large，so lateral reinforce-ment should be carried out．


Biological Engineering

Cultivation of Streptococcus thermophilus H2 and the Evaluation on Its Prebiotic Properties in Chinese Traditional Fermented Milk



LIU Dongmei, HU Jinshuang, HUANG Yongyao, et al

2020, 48(9):  133-140,148.  doi:10.12141/j.issn.1000-565X.200075

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To promote the independent research and development of domestic dairy starter，Streptococcus ther-mophilus H2 was isolated from Inner Mongolia traditional fermented milk． The composition of culture medium was optimized by response surface methodology，and the probiotic characteristics in vitro of strain H2 were evaluated by in vitro analysis． The results show that，the number of viable bacteria can reach 4. 20 ×10⁹ CFU/mL，37. 8 times larger than that before optimization，when the nitrogen source is 45.25g/L yeast extract，growth factor is 169. 5mg/L cysteine，buffer system supplement is 0. 705 g/L calcium carbonate，and the culture temperature is 40 ℃，initial pH value is 5. 5，inoculum size is 3. 5%． Evaluation of the probiotic characteristics in vitro show that the survival rate of Streptococcus thermophilus H2 is 49. 65% when pH is 3 and 99. 62% when bile salt is 0. 3%． Many kinds of fermentation metabolites，such as L-lactate，formic acid，acetic acid，propionic acid，isobutyric acid and isovaleric acid，were detected by high performance liquid chromatography (HPLC) in fermentation supernatant of H2． The concentration of L-lactate is up to 12. 64mmol/L，and D-lactate is not detected． The supernatant of H2 has scaven-ging effect on three free radicals，of which the scavenging rate of 1，1-diphenyl-2-trinitrophenylhydrazine (DPPH) was the highest，reaching 94. 06%．


Screening，Expression and Specificity Detection of Anti-VEGF Nanobodies



XIE Qiuling, LUO Meihua, LEI Yun, et al

2020, 48(9):  141-148.  doi:10.12141/j.issn.1000-565X.190667

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ascular endothelial growth factor (VEGF) is a highly specific pro-vascular endothelial growth factor that closely related to tumor invasion，metastasis，prognosis and recurrence． This study is to screen and express the nanobodies with specificity and affinity for VEGF． Firstly，the llama was immunized with VEGF，and total RNA from peripheral blood lymphocytes was extracted to construct a phage library． The clones with affinity to VEGF were screened after repeated panning，and 10 VHH gene fragments with affinity to VEGF were obtained． Then their hy-drophilicity and molecular mass were analyzed by ExPASy，and it was found that 10 Nb_VEGF proteins were hydrophi-lic proteins with molecular masses between 20. 1kDa and 20. 7 kDa． At the same time，the 10 Nb_VEGF proteins were reconstructed in Escherichia coli，and the purity of the Nb VEGF proteins purified by Ni metal chelate affinity chroma-tography all exceeds 80%． Finally the specificity of the recombinant nanobodies was detected by enzyme linked im-munosorbent assay (ELISA)． The results suggests that three recombinant nanobodies，namely，Nb_VEGF-3，Nb_VEGF-7 and Nb_VEGF-10，can specifically bind with VEGF，the affinity of Nb_VEGF-3 is consistent with that of the positive control，and other nanobodies have no resistance． In this study，three nanobodies with specificity to VEGF were screened and expressed in E. coli successfully，and Nb_VEGF-3 shows good affinity with VEGF，so it could be a drug candidate against VEGF．