In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element m...In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element model.In the new method,the finite element model was replaced by the multi-output support vector regression machine(MSVR).The interval variables of the measured frequency were sampled by Latin hypercube sampling method.The samples of frequency were regarded as the inputs of the trained MSVR.The outputs of MSVR were the target values of design parameters.The steel structure of National Aquatic Center for Beijing Olympic Games was introduced as a case for finite element model updating.The results show that the proposed method can avoid solving the problem of complicated calculation.Both the estimated values and associated uncertainties of the structure parameters can be obtained by the method.The static and dynamic characteristics of the updated finite element model are in good agreement with the measured data.展开更多
With the wide application and promotion of steel structure in China, the technical problems of complex structure construction are increasingly prominent. Combined with the mechanics and key technical points in structu...With the wide application and promotion of steel structure in China, the technical problems of complex structure construction are increasingly prominent. Combined with the mechanics and key technical points in structural mechanics, relevant designers effectively analyze the technical difficulties that need to be solved in the overall construction and installation process of steel structure. Taking a construction project as an example, this paper analyzes the difficulties and key points in the construction of the project, and on this basis, analyzes the implementation requirements and control key points of the main processes in the construction of the project, such as vertical/horizontal truss hoisting, high-altitude welding, metal curtain wall installation, etc., and puts forward corresponding measures, so as to provide reference for the implementation of such projects.展开更多
In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong ea...In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.展开更多
In a convective scheme featuring a discretized cloud size density, the assumed lateral mixing rate is inversely proportional to the exponential coefficient of plume size. This follows a typical assumption of-1, but it...In a convective scheme featuring a discretized cloud size density, the assumed lateral mixing rate is inversely proportional to the exponential coefficient of plume size. This follows a typical assumption of-1, but it has unveiled inherent uncertainties, especially for deep layer clouds. Addressing this knowledge gap, we conducted comprehensive large eddy simulations and comparative analyses focused on terrestrial regions. Our investigation revealed that cloud formation adheres to the tenets of Bernoulli trials, illustrating power-law scaling that remains consistent regardless of the inherent deep layer cloud attributes existing between cloud size and the number of clouds. This scaling paradigm encompasses liquid, ice, and mixed phases in deep layer clouds. The exponent characterizing the interplay between cloud scale and number in the deep layer cloud, specifically for liquid, ice, or mixed-phase clouds, resembles that of shallow convection,but converges closely to zero. This convergence signifies a propensity for diminished cloud numbers and sizes within deep layer clouds. Notably, the infusion of abundant moisture and the release of latent heat by condensation within the lower atmospheric strata make substantial contributions. However, this role in ice phase formation is limited. The emergence of liquid and ice phases in deep layer clouds is facilitated by the latent heat and influenced by the wind shear inherent in the middle levels. These interrelationships hold potential applications in formulating parameterizations and post-processing model outcomes.展开更多
A stabilized finite element algorithm potential for wind-structure interaction(WSI) problem is presented in this paper. Streamline upwind Petrov-Galerkin(SUPG) scheme of the large eddy simulation(LES) of dynamic sub-g...A stabilized finite element algorithm potential for wind-structure interaction(WSI) problem is presented in this paper. Streamline upwind Petrov-Galerkin(SUPG) scheme of the large eddy simulation(LES) of dynamic sub-grid scale(DSGS) is developed under the framework of arbitrary Lagrangian-Eulerian(ALE) description to solve the governing equations. High stabilization is achieved by a three-step technique in the temporal discretization. On the other hand, the partitioned procedure is employed for the consideration of the coupled WSI problem. Newmark integral method is introduced for the computation of structure domain, while spring analogy method is used for the grid update of the mesh domain. The developed computational codes are applied to the analysis of wind-induced effect of a spatial latticed structure. The numerical predictions of the three-dimensional wind flow features, the wind pressures and the wind-induced effect of spatial structures are given. Comparisons are made between the effects of rigid structure in view of the WSI.展开更多
There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into ...There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into two areas for lifting, and there are four different areas for different repair welding areas and lifting methods. By analyzing the indexes of stress, deformation and internal force of structure construction under different construction zoning schemes, the best construction scheme can be selected. The calculation results show that the construction deformation of the second scheme is the smallest, with the final deformation of 49.164mm, the maximum stress ratio of the components after construction being 0.204, and the stress ratio of the components under the load of 1.3D+1.5L being 0.8098, which is basically the same as the stress ratio of 0.80 obtained by the one-time loading design, so the second scheme is finally selected.展开更多
Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on...Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the com- bined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this pa- per with the frequency domain method as the first application of method for the analysis of the wind re- sponse of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure act- ing on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the de- sign of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by nu- merical analyses of practical projects.展开更多
青藏高原东部金沙江高山峡谷发育有众多大型深层滑坡,复杂的地形地质环境与强烈的构造地质活动塑造出该区滑坡多层次、多期次、多类型叠加的演化过程。然而,针对高山峡谷区大型深层滑坡空间结构特征的研究,目前仍是地质灾害调查与防灾...青藏高原东部金沙江高山峡谷发育有众多大型深层滑坡,复杂的地形地质环境与强烈的构造地质活动塑造出该区滑坡多层次、多期次、多类型叠加的演化过程。然而,针对高山峡谷区大型深层滑坡空间结构特征的研究,目前仍是地质灾害调查与防灾减灾工作中的重点和难点。在金沙江流域巴塘县地巫乡段,分布着一系列大型深层滑坡,其中地巫乡滑坡变形显著,已实施村庄搬迁避让措施,但其深部结构特征仍不清晰。为进一步研究区域大型深层滑坡空间结构特征,综合采用现场调查、遥感解译、无人机激光探测与测距(light detection and ranging,LiDAR)航测、高密度电法和微动探测等多种技术,查明地巫乡滑坡空间发育特征。研究认为,地巫乡滑坡地表变形强烈,主要表现为拉张裂缝、挡墙开裂和下错陡坎等形式,滑坡区内共识别出152个次级滑坡;高密度电法结果显示,地巫乡滑坡整体呈低电阻率状态,局部区域呈现高电阻率状态;微动探测揭示了滑坡地层结构,可划分为浅表覆盖层、中-强风化基岩层和弱-未风化基岩层3层;综合两种物探手段的探测结果认为,该滑坡发育由2~3层滑带,滑带位置电阻率变化显著,多呈低阻状态,电阻率值为100~150Ω·m,最大埋深可达70 m。两种方法探测结果一致性较高,所获滑体厚度相对误差在10%以内。基于建立的高山峡谷区大型深层滑坡空间结构探测的物探响应技术流程,可以较好地指导高山峡谷区大型深层滑坡的空间结构探测。展开更多
基金Project(50678052) supported by the National Natural Science Foundation of China
文摘In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element model.In the new method,the finite element model was replaced by the multi-output support vector regression machine(MSVR).The interval variables of the measured frequency were sampled by Latin hypercube sampling method.The samples of frequency were regarded as the inputs of the trained MSVR.The outputs of MSVR were the target values of design parameters.The steel structure of National Aquatic Center for Beijing Olympic Games was introduced as a case for finite element model updating.The results show that the proposed method can avoid solving the problem of complicated calculation.Both the estimated values and associated uncertainties of the structure parameters can be obtained by the method.The static and dynamic characteristics of the updated finite element model are in good agreement with the measured data.
文摘With the wide application and promotion of steel structure in China, the technical problems of complex structure construction are increasingly prominent. Combined with the mechanics and key technical points in structural mechanics, relevant designers effectively analyze the technical difficulties that need to be solved in the overall construction and installation process of steel structure. Taking a construction project as an example, this paper analyzes the difficulties and key points in the construction of the project, and on this basis, analyzes the implementation requirements and control key points of the main processes in the construction of the project, such as vertical/horizontal truss hoisting, high-altitude welding, metal curtain wall installation, etc., and puts forward corresponding measures, so as to provide reference for the implementation of such projects.
基金Supported by:National Science Fund for Distinguished Young Scholars of China Under Grant No. 50425824the National Natural Science Foundation of China Under Grant No.50578109,90715034 and 90715032
文摘In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (Grant No.2019QZKK010203)the National Natural Science Foundation of China (Grant No.42175174 and 41975130)+1 种基金the Natural Science Foundation of Sichuan Province (Grant No.2022NSFSC1092)the Sichuan Provincial Innovation Training Program for College Students (Grant No.S202210621009)。
文摘In a convective scheme featuring a discretized cloud size density, the assumed lateral mixing rate is inversely proportional to the exponential coefficient of plume size. This follows a typical assumption of-1, but it has unveiled inherent uncertainties, especially for deep layer clouds. Addressing this knowledge gap, we conducted comprehensive large eddy simulations and comparative analyses focused on terrestrial regions. Our investigation revealed that cloud formation adheres to the tenets of Bernoulli trials, illustrating power-law scaling that remains consistent regardless of the inherent deep layer cloud attributes existing between cloud size and the number of clouds. This scaling paradigm encompasses liquid, ice, and mixed phases in deep layer clouds. The exponent characterizing the interplay between cloud scale and number in the deep layer cloud, specifically for liquid, ice, or mixed-phase clouds, resembles that of shallow convection,but converges closely to zero. This convergence signifies a propensity for diminished cloud numbers and sizes within deep layer clouds. Notably, the infusion of abundant moisture and the release of latent heat by condensation within the lower atmospheric strata make substantial contributions. However, this role in ice phase formation is limited. The emergence of liquid and ice phases in deep layer clouds is facilitated by the latent heat and influenced by the wind shear inherent in the middle levels. These interrelationships hold potential applications in formulating parameterizations and post-processing model outcomes.
基金the National Natural Science Foundation of China(Nos.11172174 and 51278297)the Research Program of Shanghai Leader Talent(No.20)the Doctoral Disciplinary Special Research Project of Chinese Ministry of Education(No.20130073110096)
文摘A stabilized finite element algorithm potential for wind-structure interaction(WSI) problem is presented in this paper. Streamline upwind Petrov-Galerkin(SUPG) scheme of the large eddy simulation(LES) of dynamic sub-grid scale(DSGS) is developed under the framework of arbitrary Lagrangian-Eulerian(ALE) description to solve the governing equations. High stabilization is achieved by a three-step technique in the temporal discretization. On the other hand, the partitioned procedure is employed for the consideration of the coupled WSI problem. Newmark integral method is introduced for the computation of structure domain, while spring analogy method is used for the grid update of the mesh domain. The developed computational codes are applied to the analysis of wind-induced effect of a spatial latticed structure. The numerical predictions of the three-dimensional wind flow features, the wind pressures and the wind-induced effect of spatial structures are given. Comparisons are made between the effects of rigid structure in view of the WSI.
文摘There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into two areas for lifting, and there are four different areas for different repair welding areas and lifting methods. By analyzing the indexes of stress, deformation and internal force of structure construction under different construction zoning schemes, the best construction scheme can be selected. The calculation results show that the construction deformation of the second scheme is the smallest, with the final deformation of 49.164mm, the maximum stress ratio of the components after construction being 0.204, and the stress ratio of the components under the load of 1.3D+1.5L being 0.8098, which is basically the same as the stress ratio of 0.80 obtained by the one-time loading design, so the second scheme is finally selected.
基金Supported by the National Natural Science Foundation of China (No. 50178035)
文摘Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the com- bined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this pa- per with the frequency domain method as the first application of method for the analysis of the wind re- sponse of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure act- ing on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the de- sign of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by nu- merical analyses of practical projects.
文摘青藏高原东部金沙江高山峡谷发育有众多大型深层滑坡,复杂的地形地质环境与强烈的构造地质活动塑造出该区滑坡多层次、多期次、多类型叠加的演化过程。然而,针对高山峡谷区大型深层滑坡空间结构特征的研究,目前仍是地质灾害调查与防灾减灾工作中的重点和难点。在金沙江流域巴塘县地巫乡段,分布着一系列大型深层滑坡,其中地巫乡滑坡变形显著,已实施村庄搬迁避让措施,但其深部结构特征仍不清晰。为进一步研究区域大型深层滑坡空间结构特征,综合采用现场调查、遥感解译、无人机激光探测与测距(light detection and ranging,LiDAR)航测、高密度电法和微动探测等多种技术,查明地巫乡滑坡空间发育特征。研究认为,地巫乡滑坡地表变形强烈,主要表现为拉张裂缝、挡墙开裂和下错陡坎等形式,滑坡区内共识别出152个次级滑坡;高密度电法结果显示,地巫乡滑坡整体呈低电阻率状态,局部区域呈现高电阻率状态;微动探测揭示了滑坡地层结构,可划分为浅表覆盖层、中-强风化基岩层和弱-未风化基岩层3层;综合两种物探手段的探测结果认为,该滑坡发育由2~3层滑带,滑带位置电阻率变化显著,多呈低阻状态,电阻率值为100~150Ω·m,最大埋深可达70 m。两种方法探测结果一致性较高,所获滑体厚度相对误差在10%以内。基于建立的高山峡谷区大型深层滑坡空间结构探测的物探响应技术流程,可以较好地指导高山峡谷区大型深层滑坡的空间结构探测。
