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China Ocean engineering 2024年第2期38卷 285-296页

作者： DU Zun-feng ZHU Hai-ming YU Jian-xing State Key Laboratory of Hydraulic engineering Intelligent Construction and Operation School of Civil EngineeringTianjin UniversityTianjin 300350China

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.

关键词： motion reconstruction vortex-induced vibration(VIV) marine riser modal decomposition method compressed sensing

Effects of Atmospheric Pressure on Developmental Characteristics and the Stability of Air Entraining Agent for Concrete

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 979-989页

作者：李立辉牛开民 TIAN Bo CHEN Xin FU Ziqian ZHU Xuwei school of civil engineering Chongqing Jiaotong UniversityChongqing 400074China transportation Science and engineering Harbin Institute of TechnologyHarbin 150090China Research Institute of Highway Ministry of TransportBeijing 100088China

In order to ascertain the effects of atmospheric pressure on developmental characteristics and the stability of AEA(air-entraining agent)solution bubbles,AEA solution experiments and AEA solution bubble experiments were,respectively,conducted in Peking(50 m,101.2 kPa)and Lhasa(3,650 m,63.1 kPa).Surface tensions and inflection-point concentrations were tested based on AEA solutions,whilst developmental characteristics,thicknesses and elastic coefficients of liquid films were tested based on air bubbles of AEA solutions.The study involved three types of AEAs,which were TM-O,226A,and 226S.The experimental results show that initial sizes of TM-O,226A,and 226S are,respectively,increased by 43.5%,17.5%,and 3.8%.With the decrease of ambient pressure,the drainage rate and the drainage index of AEA solution bubbles increase.Interference experiments show that the liquid film thicknesses of all tested AEA solution bubbles are in micron scales.When the atmospheric pressure decreases from 101.2 to 63.1 kPa,the liquid film thicknesses of three types of AEA solutions decrease in various degrees;and film elasticities at critical thicknesses increase.Liquid film of 226S solution bubbles is the most stable,presenting as a minimum thickness variation.It should be noted that elastic coefficient of liquid film only represents the level at critical thickness,thus it can not be applied as the only evaluating indicator of bubble stability.For a type of AEA,factors affecting the stability of its bubbles under low atmospheric pressure include initial bubbles size,liquid film thickness,liquid film elasticity,ambient temperature,etc.

关键词： air-entraining agent surface tension bubble size liquid film thickness liquid film elasticity atmospheric pressure

Construction Activity Analysis of Workers Based on Human Posture Estimation Information

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engineering 2024年第2期33卷 225-236页

作者： Xuhong Zhou Shuai Li Jiepeng Liu Zhou Wu Yohchia Frank Chen school of civil engineering Chongqing UniversityChongqing 400044China school of Automation Chongqing UniversityChongqing 400044China Department of civil engineering The Pennsylvania State UniversityMiddletownPA 17057USA

Identifying workers’construction activities or behaviors can enable managers to better monitor labor efficiency and construction progress.However,current activity analysis methods for construction workers rely solely on manual observations and recordings,which consumes considerable time and has high labor costs.Researchers have focused on monitoring on-site construction activities of workers.However,when multiple workers are working together,current research cannot accu rately and automatically identify the construction activity.This research proposes a deep learning framework for the automated analysis of the construction activities of multiple workers.In this framework,multiple deep neural network models are designed and used to complete worker key point extraction,worker tracking,and worker construction activity analysis.The designed framework was tested at an actual construction site,and activity recognition for multiple workers was performed,indicating the feasibility of the framework for the automated monitoring of work efficiency.

关键词： Pose estimation Activity analysis Object tracking Construction workers Automatic systems

Finite Element Simulations on Failure Behaviors of Granular Materials with Microstructures Using a Micromechanics-Based Cosserat Elastoplastic Model

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Computer Modeling in engineering & Sciences 2024年第3期138卷 2305-2338页

作者： Chenxi Xiu Xihua Chu school of civil engineering Chongqing Jiaotong UniversityChongqing400074China school of civil engineering Wuhan UniversityWuhan430072China

This paper presents a micromechanics-based Cosserat continuum model for microstructured granular materials.By utilizing this model,the macroscopic constitutive parameters of granular materials with different microstructures are expressed as sums of microstructural information.The microstructures under consideration can be classified into three categories:a medium-dense microstructure,a dense microstructure consisting of one-sized particles,and a dense microstructure consisting of two-sized particles.Subsequently,the Cosserat elastoplastic model,along with its finite element formulation,is derived using the extended Drucker-Prager yield criteria.To investigate failure behaviors,numerical simulations of granular materials with different microstructures are conducted using the ABAQUS User Element(UEL)interface.It demonstrates the capacity of the proposed model to simulate the phenomena of strain-softening and strain localization.The study investigates the influence of microscopic parameters,including contact stiffness parameters and characteristic length,on the failure behaviors of granularmaterials withmicrostructures.Additionally,the study examines themesh independence of the presented model and establishes its relationship with the characteristic length.A comparison is made between finite element simulations and discrete element simulations for a medium-dense microstructure,revealing a good agreement in results during the elastic stage.Somemacroscopic parameters describing plasticity are shown to be partially related to microscopic factors such as confining pressure and size of the representative volume element.

关键词： Granular materials micromechanics Cosserat elastoplastic model microstructures failure behaviors

Limit load and failure mechanisms of a vertical Hoek-Brown rock slope

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Journal of Rock Mechanics and Geotechnical engineering 2024年第3期16卷 1106-1111页

作者： Jim Shiau Warayut Dokduea Suraparb Keawsawasvong Pitthaya Jamsawang school of engineering University of Southern QueenslandToowoomba4350QLDAustralia Department of civil engineering Faculty of EngineeringKing Mongkut’s University of Technology ThonburiBangkokThailand Research Unit in Sciences and Innovative Technologies for civil engineering Infrastructures Department of Civil EngineeringThammasat School of EngineeringThammasat UniversityPathumthani12120Thailand Soil engineering Research Center Department of Civil EngineeringKing Mongkut’s University of Technology North BangkokBangkok10800Thailand

The problem considered in this short note is the limit load determination of a vertical rock slope.The classical limit theorem is employed with the use of adaptive finite elements and nonlinear programming to determine upper and lower bound limit loads of a Hoek-Brown vertical rock slope.The objective function of the mathematical programming problem is such as to optimize a boundary load,which is known as the limit load,resembling the ultimate bearing capacity of a strip footing.While focusing on the vertical slope,parametric studies are carried out for several dimensionless ratios such as the dimensionless footing distance ratio,the dimensionless height ratio,and the dimensionless rock strength ratio.A comprehensive set of design charts is presented,and failure envelopes shown with the results explained in terms of three identified failure mechanisms,i.***.the face,the toe,and the Prandtl-type failures.These novel results can be used with great confidence in design practice,in particularly noting that the current industry-based design procedures for the presented problem are rarely found.

关键词： Bearing capacity Rock slope Vertical slope Finite element limit analysis Hoek-Brown yield criterion

Closed-Form Solution for a Circular Nanohole with Surface Effects Under Uniform Heat Flux

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Acta Mechanica Solida Sinica 2024年第1期37卷 43-52页

作者： Jieyao Tang Jieyan Zhao Haibing Yang Cunfa Gao State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China school of civil engineering and transportation South China University of TechnologyGuangzhou 510641China College of Mechanics and Materials Hohai UniversityNanjing 211100China

This paper investigates the steady-state thermoelastic problem of a circular nanohole embedded in an infinitely large elastic plane subjected to a uniform far-field heat flux.A lowly conductive surface model is used to account for the effects of surface phonon scattering,while the complete Gurtin–Murdoch model is utilized to characterize the effects of surface tension and surface elasticity.The closed-form solution to the temperature and stress field surrounding the hole is derived in the context of complex variable methods.Several numerical examples are presented to analyze the influence of surface effects on thermal stress fields.It is shown that surface effects induce notable increases in normal and shear stresses around the hole.Specifically,all three stress components(hoop,normal,and shear)in the vicinity of the hole exhibit substantial augmentation with increasing surface tension and surface modulus.In particular,it is found that the presence of surface effects amplifies the variation in stress gradients and intensifies stress concentration around the hole.

关键词： Circular nanohole Surface effect Thermal stress Heat flux

Detection of internal crack growth in polyethylene pipe using guided wave ultrasonic testing

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Earthquake engineering and engineering Vibration 2024年第2期23卷 319-329页

作者： Jay Kumar Shah Hao Wang Said El-Hawwat Centre of Advanced Infrastructure and transportation RutgersThe State University of New JerseyNJ 08854USA Department of civil and Environmental engineering RutgersThe State University of New JerseyNJ 08854USA

Despite the success of guided wave ultrasonic inspection for internal defect detection in steel pipes,its application on polyethylene(PE)pipe remains relatively unexplored.The growth of internal cracks in PE pipe severely affects its pressure-holding capacity,hence the early detection of internal cracks is crucial for effective pipeline maintenance strategies.This study extends the scope of guided wave-based ultrasonic testing to detect the growth of internal cracks in a natural gas distribution PE pipe.Laboratory experiments and a finite element model were planned to study the wave-crack interaction at different stages of axially oriented internal crack growth with a piezoceramic transducer-based setup arranged in a pitch-catch configuration.Mode dispersion analysis supplemented with preliminary experiments was performed to isolate the optimal inspection frequency,leading to the selection of the T(0,1)mode at 50-kHz for the investigation.A transmission index based on the energy of the T(0,1)mode was developed to trace the extent of simulated crack growth.The findings revealed an inverse linear correlation between the transmission index and the crack depth for crack growth beyond 20%crack depth.

关键词： polyethylene pipes internal cracks guided wave ultrasonic testing torsional modes finite element modeling

WT-FCTGN:A wavelet-enhanced fully connected time-gated neural network for complex noisy traffic flow modeling

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Chinese Physics B 2024年第7期 662-675页

作者：廖志芳孙轲刘文龙余志武刘承光宋禹成 school of Computer Science and engineering Central South University National engineering Research Center of High-speed Railway Construction Technology school of civil engineering Central South University school of Traffic & transportation engineering Central South University

Accurate forecasting of traffic flow provides a powerful traffic decision-making basis for an intelligent transportation system. However, the traffic data's complexity and fluctuation, as well as the noise produced during collecting information and summarizing original data of traffic flow, cause large errors in the traffic flow forecasting results. This article suggests a solution to the above mentioned issues and proposes a fully connected time-gated neural network based on wavelet reconstruction(WT-FCTGN). To eliminate the potential noise and strengthen the potential traffic trend in the data, we adopt the methods of wavelet reconstruction and periodic data introduction to preprocess the data. The model introduces fully connected time-series blocks to model all the information including time sequence information and fluctuation information in the flow of traffic, and establishes the time gate block to comprehend the periodic characteristics of the flow of traffic and predict its flow. The performance of the WT-FCTGN model is validated on the public Pe MS data set. The experimental results show that the WT-FCTGN model has higher accuracy, and its mean absolute error(MAE), mean absolute percentage error(MAPE) and root mean square error(RMSE) are obviously lower than those of the other algorithms. The robust experimental results prove that the WT-FCTGN model has good anti-noise ability.

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Quantitative measurement and application of droplets on physical surfaces based on LIF technology

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transportation Safety and Environment 2024年第2期6卷 104-113页

作者： Fan Wu Shuaixiong Zhou Qingmin Cui Renze Xu Hengkui Li Chao Yu Key Labor atory of Traffic Safety on Track of Ministry of Education School of Traffic&Transportation EngineeringCentr al South Univ ersityChangsha 410075HunanChina Joint International Research Laboratory of Key Technologies for Rail Traffic Safety School of Traffic&Transportation EngineeringCentral South UniversityChangsha 410075HunanChina school of software Henan University of EngineeringZhengzhou 451191HenanChina National&Local Joint engineering Research Center of Safety Technology for Rail Vehicle School of Traffic&Transportation EngineeringCentral South UniversityChangsha 410075HunanChina

Contaminated surfaces play a significant role in the transmission of respiratory infectious diseases.To address this issue,we pre-sented a novel quantitative detection method for droplets on physical surfaces,based on the laser-induced fluorescence technique.The proposed detection method was demonstrated in a realistic high-speed train compartment scenario by simulating the process of droplet release during passengers’breathing and coughing.The experimental results showed that this method could offer high precision(10-1 mg/m^(2))for detecting minute substance concentrations,and its ease of operation makes it suitable for complex en-gineering environments.The results also revealed that under the combined effects of the indoor airflow and breathing airflow,the range of droplets released by breathing activity exceeded two rows in front of and behind the release position.Simultaneously,we observed that a large number of droplets settled on the seat surfaces on both sides of the same row as the releaser,with over 36%of these droplets concentrated on the backrest area of the seats.As the respiratory jet velocity increased,the location with the most sed-iment droplets(accounting for 8%of the total sedimentation)occurred on the seat directly in front of the releaser,and approximately 48% of the droplets were found on the back of this seat.Our proposed method overcomes the shortcomings of existing experimental methods in quantitatively capturing the motion characteristics of droplets in complex flow fields.

关键词： quantitative measurement sediment droplets physical surfaces fluorescence measurement high-speed train compart-ment

Simplified seismic scenario analysis of existing masonry buildings accounting for local site effects

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Frontiers of Structural and civil engineering 2024年第2期18卷 309-318页

作者： Ayşe E.ÖZSOYÖZBAY Işıl SANRI KARAPINAR Zehra N.KUTLU İsmail E.KILIÇ Department of civil engineering Maltepe UniversityIstanbul 34857Turkey school of engineering and Construction Oryx Universal CollegeDoha 12253Qatar

This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry buildings.In this context,a rapid seismic evaluation procedure was implemented on an old masonry building stock in the historical center Galata,located inİstanbul,to determine the seismic risk priority of the built heritage.Damage scenarios were generated for all soil classes,different moment magnitudes,and source-to-site distances to obtain more accurate results for the seismic vulnerability assessment of the studied building stock.Consequently,damage distributions estimated under nine different scenarios with/without site effects were compared and illustrated in maps to discuss changes in vulnerability owing to amplification effects.In this study,by re-examining the rapid seismic evaluation procedure by including geo-hazard-based assessment,the importance of site effects on the vulnerability and risk assessment of built heritage was underlined.The proposed framework integrating field data and local site effects is believed to advance the current applications for vulnerability assessment of masonry buildings and provide an improvement in the application of rapid seismic assessment procedures with more reliable results.

关键词： masonry buildings seismic vulnerability assessment cultural heritage local site effect