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AWells-Riley/based COVID-19 infectiousrisk assessment model combining both short rangeandroom scale effects

Building Simulation 2024年第1期17卷 93-111页

作者： Yinshuai Feng Yifan Fan Xiaoyu Luo Jian Ge College of Civil Engineering and architecture Zhejiang UniversityHangzhouChina center for balance architecture Zhejiang UniversityHangzhouChina International Research center for Green Building and Low-Carbon City International CampusZhejiang UniversityHainingChina

There is growing evidence of the high transmission potential of COVID-19 through virus-laden aerosols.Because aerosols are inhaled in various concentrations,an overall assessment of transmission risks at different indoor scales is crucial.However,a comprehensive risk assessment method that evaluates the direct link between short-range and room-scale zones is stl lacking.In this paper,a risk assessment model combining both short-range and room-scale effects is developed to obtain effective reproduction number in confined indoor environments,called Turbulent Jet Wells Riley(TJWR)model.Combined with the viral load data and aerosol generation data of different human respiratory activities,the Monte Carlo simulation method is applied to calculate the quanta emission rate,which further provides the input parameters of the TJWR model.Three known outbreaks(Hangzhou banquet hall X,Guangzhou restaurant Y,and Hong Kong restaurant Z,China)are chosen to validate the TJWR model.Results show that the TJWR model is more efficient than the original Wells-Riley model.The average relative error of the TJWR model ranges between 9%and 44%,while for the Wells-Riley model,it ranges between 57%and 78%.The TJWR model also proves that infection risk assessments using the well-mixed assumption can systematically underestimate the transmission risk for those close to the source.Additionally,there is a significant positive linear correlation between the total number of exposed individuals at the short-range and the effective reproduction number.This newly developed TJWR model has great potential for rapid and real-time overall airborne transmission risk assessment in buildings and cities.

关键词： COVID-19 airborne transmission infection risk Wells-Riley model Monte Carlo simulation

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Non-uniform thermal behavior of single-layer spherical reticulated shell structures considering time-variant environmental factors: analysis and design

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第3期25卷 223-237页

作者： Wucheng XU Xiaoqing ZHENG Xuanhe ZHANG Zhejie LAI Yanbin SHEN College of Civil Engineering and architecture Zhejiang UniversityHangzhou 310058China center for balance architecture Zhejiang UniversityHangzhou 310028China Innovation center of Yangtze River Delta Zhejiang UniversityJiaxing 314100China Zhejiang Provincial Key Laboratory of Space Structures Zhejiang UniversityHangzhou 310058China

Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.

关键词： Non-uniform temperature field Non-uniform thermal load Non-uniform thermal effect Single-layer spherical reticulated shell Time-variant environmental factor

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Micromechanics of Thermal Conductive Composites:Review,Developments and Applications

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Acta Mechanica Solida Sinica 2024年第2期37卷 215-237页

作者： Guannan Wang Yulin Huang Mengyuan Gao Qiang Chen Department of Civil Engineering Zhejiang UniversityHangzhou310058China center for balance architecture Zhejiang UniversityHangzhou310007China School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an710049China

Micromechanics investigations of composites with fiber-shaped reinforcement are extensively applied in the engineering design and theoretical analysis of thermal composites in the aerospace engineering and high-tech industry.In this paper,a critical review of various classical micromechanics approaches is provided based on the classification framework and the development of micromechanics tools.Several numerical micromechanics tools have been developed to overcome limitations through exactly/approximately solving the internal governing equations of microstructures.The connections and limitations of those models are also investigated and discussed,based on which three recently developed numerical or semi-analytical models are explained,including finite-element micromechanics,finite-volume direct averaging micromechanics,and locally exact homogenization theory,as well as machine learning tools.Since it is almost inevitable to mention the interfacial effects on thermal behavior of fibrous composites,we review the new mathematical relations that interrupt the original continuity conditions due to the existence of interphase/interface within unit cells.Generally speaking,the interphase/interface is demonstrated to play a significant role in influencing the effective coefficients and localized thermal fields.The present work also briefly reviews the application of micromechanics tools in emerging engineered woven composites,natural fibrous composites,and ablative thermal protection composites.It is demonstrated that sophisticated micromechanics tools are always demanded for investigating the effective and localized responses of thermal fibrous composites.

关键词： Micromechanics models Thermal fibrous composites Microstructural detail-free models Semi-analytical and numerical methods Interfacial effects Woven composites Natural composites

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Conditional Generative Adversarial Network Enabled Localized Stress Recovery of Periodic Composites

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Computer Modeling in Engineering & Sciences 2024年第7期140卷 957-974页

作者： Chengkan Xu Xiaofei Wang Yixuan Li Guannan Wang He Zhang Transportation and Municipal Engineering Institute Powerchina Huadong Engineering CorporationHangzhou310014China College of Civil Engineering and architecture Zhejiang UniversityHangzhou310058China Anhui Transport Consulting&Design Institute Co. Ltd.Hefei230088China center for balance architecture Zhejiang UniversityHangzhou310058China

Structural damage in heterogeneousmaterials typically originates frommicrostructures where stress concentration occurs.Therefore,evaluating the magnitude and location of localized stress distributions within microstructures under external loading is crucial.Repeating unit cells(RUCs)are commonly used to represent microstructural details and homogenize the effective response of composites.This work develops a machine learning-based micromechanics tool to accurately predict the stress distributions of extracted RUCs.The locally exact homogenization theory efficiently generates the microstructural stresses of RUCs with a wide range of parameters,including volume fraction,fiber/matrix property ratio,fiber shapes,and loading direction.Subsequently,the conditional generative adversarial network(cGAN)is employed and constructed as a surrogate model to establish the statistical correlation between these parameters and the corresponding localized stresses.The stresses predicted by cGAN are validated against the remaining true data not used for training,showing good agreement.This work demonstrates that the cGAN-based micromechanics tool effectively captures the local responses of composite RUCs.It can be used for predicting potential crack initiations starting from microstructures and evaluating the effective behavior of periodic composites.

关键词： Periodic composites localized stress recovery conditional generative adversarial network

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Interface failure of segmental tunnel lining strengthened with steel plates based on fracture mechanics

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Frontiers of Structural and Civil Engineering 2024年第1期18卷 137-149页

作者： Yazhen SUN Yang YU Jinchang WANG Longyan WANG School of Transportation and Geomatics Engineering Shenyang Jianzhu UniversityShenyang 110168China School of Civil Engineering Shenyang Jianzhu UniversityShenyang 110168China Institute of Transportation Engineering Zhejiang UniversityHangzhou 310058China center for balance architecture Zhejiang UniversityHangzhou310058China

Segmental tunnel lining strengthened with steel plates is widely used worldwide to provide a permanent strengthening method.Most existing studies assume an ideal steel-concrete interface,ignoring discontinuous deformation characteristics,making it difficult to accurately analyze the strengthened structure’s failure mechanism.In this study,interfacial fracture mechanics of composite material was applied to the segmental tunnel lining strengthened with steel plates,and a numerical three-dimensional solid nonlinear model of the lining structure was established,combining the extended finite element method with a cohesive-zone model to account for the discontinuous deformation characteristics of the interface.The results accurately describe the crack propagation process,and are verified by full-scale testing.Next,dynamic simulations based on the calibrated model were conducted to analyze the sliding failure and cracking of the steel-concrete interface.Lastly,detailed location of the interface bonding failure are further verified by model test.The results show that,the cracking failure and bond failure of the interface are the decisive factors determining the instability and failure of the strengthened structure.The proposed numerical analysis is a major step forward in revealing the interface failure mechanism of strengthened composite material structures.

关键词： segmental tunnel lining steel plate strengthening connecting interface cohesive-zone model extended finite element method

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A simple atomization approach enables monolayer dispersion of nano graphenes in cementitious composites with excellent strength gains

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Nano Materials Science 2024年第2期6卷 211-222页

作者： Nanxi Dang Rijiao Yang Chengji Xu Yu Peng Qiang Zeng Weijian Zhao Zhidong Zhang College of Civil Engineering and architecture Zhejiang University310058HangzhouChina center for balance architecture Zhejiang UniversityHangzhou310028China The Architectural Design&Research Institute of Zhejiang University Co. LtdHangzhou310063China Institute for Building Materials ETH Zurich8093ZurichSwitzerland

Carbon nano additives(CNAs)are critical to achieving the unique properties of functionalized composites,however,controlling the dispersion of CNAs in material matrix is always a challenging task.In this study,a simple atomization approach was successfully developed to promote the dispersion efficiency of graphene nanoplatelets(GNPs)in cement composites.This atomization approach can be integrated with the direct,indirect and combined ultrasonic stirrings in a homemade automatic stirring-atomization device.Mechanical and microstructure tests were performed on hardened cement pastes blended with GNPs in different stirring and mixing approaches.Results show that the direct ultrasonic stirrings enabled more homogeneous dispersions of GNP particles with a smaller size for a longer duration.The atomized droplets with the mean size of~100μm largely mitigated GNPs’agglomerations.Monolayer GNPs were observed in the cement matrix with the strength gain by up to 54%,and the total porosity decrease by 21%in 0.3 wt%GNPs dosage.The greatly enhanced dispersion efficiency of GNPs in cement also raised the cement hydration.This work provides an effective and manpower saving technique toward dispersing CNAs in engineering materials with great industrialization prospects.

关键词： Nanomaterials Dispersion Atomization Strength Microstructure

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Self-powered wireless environmental monitoring system for in-service bridges by galloping piezoelectric-triboelectric hybridized energy harvester

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Science China(Technological Sciences) 2024年第5期67卷 1498-1509页

作者： HUANG KangXu WANG XiaoFei WANG Li ZHOU YuHui LIU FuHai CHANG ShiYuan ZHU JunTao ZHOU YuXuan ZHANG He LUO JiKui College of Civil Engineering and architecture Zhejiang UniversityHangzhou310058China Anhui Transport Consulting&Design Institute Co. Ltd.Hefei230088China College of Electronics&Information Hangzhou Dianzi UniversityHangzhou310018China center for balance architecture Zhejiang UniversityHangzhou310058China College of Information Science&Electronic Engineering Zhejiang UniversityHangzhou310027China

The energy harvesting technology for the ubiquitous natural wind enables a desirable solution to the issue of distributed sensors in the bridge environmental sensing Internet of Things(Io T)system being restricted to conventional energy supply.In this work,a self-powered system based on a compact galloping piezoelectric-triboelectric energy harvester(GPTEH)is developed to achieve efficient wind energy harvesting.The GPTEH is constructed on the prototype of a cantilever structure with piezoelectric macro-fiber composite(MFC)sheets and a rectangular bluff body with triboelectric nanogenerators(TENGs).Through a special swing-type structural design with iron blocks inside the bluff body,the GPTEH exhibits preferable aerodynamic behavior and excellent energy conversion efficiency,compared to conventional cantilever kind of piezoelectric wind energy harvester(PWEH).The GPTEH also demonstrates the capability of high output power density(PEH of 23.65 W m^(-2)and TENG of 1.59 W m^(-2)),superior response wind speed(about 0.5 m s^(-1)),and excellent long-term stability(over 14000 cyclic tests).Furthermore,a power management system is developed to efficiently utilize the output energy from GPTEH to power the sensors and wirelessly transmit environmental data to the terminals.The proposed GPTEH-powered system exhibits a great potential for the bridge environmental monitoring and Io T technologies.

关键词： self-powered hybrid nanogenerator triboelectric nanogenerator macro-fiber composite wireless environmental monitoring system

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考虑Steigmann-Ogden界面的复合材料远场解析解

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Acta Mechanica Sinica 2024年第1期40卷 35-43页

作者：高梦园贺哲龙 Ougbe Anseme Ahehehinnou 王冠楠 Department of Civil Engineering Zhejiang UniversityHangzhou 310058China center for balance architecture Zhejiang UniversityHangzhou 310007China College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China

本文给出了含有纳米纤维或孔隙的二维异质材料在远场载荷作用下的Steigmann-Ogden弹性面的解析解.该求解与最近文献中复函数法的数值结果进行了验证,并提供了具体位移和应力场的闭式表达式.数值研究了表面弹性参数、表面残余应力、纤维... 详细信息

本文给出了含有纳米纤维或孔隙的二维异质材料在远场载荷作用下的Steigmann-Ogden弹性面的解析解.该求解与最近文献中复函数法的数值结果进行了验证,并提供了具体位移和应力场的闭式表达式.数值研究了表面弹性参数、表面残余应力、纤维/孔径和远场载荷对局部应力分布的影响.结果表明,表面弹性参数会扰乱纤维域内的内应力,而表面弯曲刚度参数会显著影响应力集中,这与经典Eshelby问题中的均匀应力分布不同.分析表达式揭示了一些有趣的现象,例如,纤维复合材料在静水载荷作用下的应力/位移场仅与表面Lamé参数有关,剪切载荷作用下分析表达式中的非常数系数保持为单轴拉伸载荷作用下的两倍,这些都是本文首次报道的.所建立的解决方案对于准确捕捉具有显著表面效应的纳米复合材料的力学响应至关重要.

关键词：纳米复合材料异质材料表面效应纤维复合材料弹性参数载荷作用剪切载荷弯曲刚度

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A Multiscale Model of Mass-Functionally Graded Beam-Fluid System Under Bending and Vibration Responses

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Acta Mechanica Solida Sinica 2024年第2期37卷 327-340页

作者： Lei Zhang Jianping Lin Jiaqing Jiang Guannan Wang Department of Civil Engineering Zhejiang University866 Yuhangtang RoadHangzhou310058China center for balance architecture Zhejiang UniversityHangzhou310007China College of Civil Engineering Huaqiao UniversityXiamen361021China Key Laboratory for Intelligent Infrastructure and Monitoring of Fujian Province Huaqiao UniversityXiamen361021China Department of Engineering Mechanics Zhejiang UniversityHangzhou310027China

In this paper,a multiscale model is developed for the mass functionally graded(FG)beam-fluid system to investigate its static and dynamic responses based on 3D printed porous beam free vibration tests,which are determined by two aspects.At the microstructural level,the gradient variation is realized by arbitrary distribution of matrix pores,and the effective moduli under specific distribution are obtained using the micromechanics homogenization theory.In the meantime,at the structural level,the mechanical responses of FG porous beams subjected to mass loading are considered in a static fluid environment.Then,the explicit expressions of local finite-element(FE)expressions corresponding to the static and dynamic responses are given in the appendices.The present results are validated against numerical and experimental results from the literature and mechanical tests of 3D printed structures,with good agreement generally obtained,giving credence to the present model.On this basis,a comprehensive parametric study is carried out,with a particular focus on the effects of boundary conditions,fluid density,and slenderness ratio on the bending and vibration of FG beams with several different gradations.

关键词： 3D printed test Mass functionally graded beam-fluid system Multiscale model Local finite-element expressions Static bending Free vibration

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An approach for determination of lateral limit angle in kinematic planar sliding analysis for rock slopes

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1305-1314页

作者： Xiaojuan Yang Jie Hu Honglei Sun Jun Zheng College of Civil Engineering Zhejiang University of TechnologyHangzhou310023China Department of Civil Engineering Zhejiang UniversityHangzhou310058China center for balance architecture Zhejiang UniversityHangzhou310007China The Architectural Design & Research Institute of Zhejiang University Co. Ltd.Hangzhou310063China

Planar sliding is one of the frequently observed types of failure in rock slopes.Kinematic analysis is a classic and widely used method to examine the potential failure modes in rock masses.The accuracy of planar sliding kinematic analysis is significantly influenced by the value assigned to the lateral limit angleγlim.However,the assignment ofγlim is currently used generally based on an empirical criterion.This study aims to propose an approach for determining the value ofγlim in deterministic and probabilistic kinematic planar sliding analysis.A new perspective is presented to reveal thatγlim essentially influences the probability of forming a potential planar sliding block.The procedure to calculate this probability is introduced using the block theory method.It is found that the probability is correlated with the number of discontinuity sets presented in rock masses.Thus,different values ofγlim for rock masses with different sets of discontinuities are recommended in both probabilistic and deterministic planar sliding kinematic analyses;whereas a fixed value ofγlim is commonly assigned to different types of rock masses in traditional method.Finally,an engineering case was used to compare the proposed and traditional kinematic analysis methods.The error rates of the traditional method vary from 45%to 119%,while that of the proposed method ranges between 1%and 17%.Therefore,it is likely that the proposed method is superior to the traditional one.

关键词： Kinematic analysis Block theory Planar sliding Lateral limit angle Rock slope

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