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Determination of Monitoring Control Value for Concrete Gravity Dam Spatial Deformation Based on POT Model

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Computer Modeling in Engineering & Sciences 2023年第6期135卷 2119-2135页

作者： Zhiwen Xie tiantang yu Department of Engineering Mechanics Hohai UniversityNanjing211100China

Deformation can directly reflect the working behavior of the dam,so determining the deformation monitoring control value can effectively monitor the safety of dam *** traditional dam deformation monitoring control value only considers the single measuring *** order to overcome the limitation,this paper presents a new method to determine the monitoring control value for concrete gravity dam based on the deformations of multi-measuring points.A dam’s comprehensive deformation displacement is determined by the measured values at different measuring points on the positive inverted vertical line and the corresponding weight of eachmeasuring *** projection pursuit method(PPM)combined with the grey wolf optimization(GWO)algorithm is used to determine the weight of each measuring point according to the spatial correlation distribution characteristics of dam *** peaks over threshold(POT)model based on the extreme value theory is adopted to determine the monitoring control value with the obtained dam comprehensive deformation *** addition,the POTmodel is improved with the automatic threshold determinationmethod based on the 3σcriterion in probability theory and the GWO algorithm,which can avoid subjectivity and randomness in determining the *** results of the engineering application show the feasibility and applicability of the proposed method.

关键词： Concrete gravity dam deformation monitoring control value PPM GWO POT

Adaptive Extended Isogeometric Analysis for Steady-State Heat Transfer in Heterogeneous Media

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Computer Modeling in Engineering & Sciences 2021年第3期126卷 1315-1332页

作者： Weihua Fang tiantang yu Yin Yang Nanjing Automation Institute of Water Conservancy and Hydrology Ministry of Water ResourcesNanjing210012China Department of Engineering Mechanics Hohai UniversityNanjing211100China Lake Research Institute Hydraulic Research Institute of Jiangsu ProvinceNanjing210017China

Steady-state heat transfer problems in heterogeneous solid are simulated by developing an adaptive extended isogeometric analysis(XIGA)method based on locally refined non-uniforms rational B-splines(LR NURBS).In the XIGA,the LR NURBS,which have a simple local refinement algorithm and good description ability for complex geometries,are employed to represent the geometry and discretize the field variables;and some special enrichment functions are introduced into the approximation of temperature field,thus the computational mesh is independent of the material interfaces,which are described with the level *** to the approximation of temperature field,a temperature gradient recovery technique for heterogeneous media is proposed,and based on the Zienkiewicz–Zhu recovery technique a posteriori error estimator is defined to automatically identify the locally refined *** convergence and performance properties of the developed method are verified by using three numerical *** numerical results show that(1)The convergence speed of the adaptive local refinement is faster than that of the uniform global refinement;(2)The convergence rate of the high-order basis functions is faster than that of the low-order basis functions;and(3)The existing inclusions change the local distributions of the temperature,and the extreme values of the temperature gradients take place around the inclusion interfaces.

关键词： Heterogeneous media steady-state heat transfer adaptive XIGA LR NURBS heat dissipation

Numerical modeling of concrete hydraulic fracturing with extended finite element method

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Science China(Technological Sciences) 2009年第3期52卷 559-565页

作者： REN QingWen DONG yuWen yu tiantang Department of Engineering Mechanics Hohai UniversityNanjing 210098China College of River and Ocean Engineering Chongqing Jiaotong UniversityChongqing 400074China

The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan- tages of the XFEM for hydraulic fracturing analysis are displayed.

关键词： extended finite element method (XFEM) hydraulic fracture concrete numerical modeling

Modeling Geometrically Nonlinear FG Plates: A Fast and Accurate Alternative to IGA Method Based on Deep Learning

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Computer Modeling in Engineering & Sciences 2024年第3期138卷 2793-2808页

作者： Se Li tiantang yu Tinh Quoc Bui College of Mechanics and Materials Hohai UniversityNanjing211100China Duy Tan Research Institute for Computational Engineering(DTRICE) Duy Tan UniversityHo Chi Minh CityVietnam

Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element *** IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.

关键词： FG plates geometric nonlinearity deep learning BLSTM IGA S-FSDT

Isogeometric Analysis for the Arbitrary AFG Microbeam with Two-Phase Nonlocal Stress-Driven Model

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Acta Mechanica Solida Sinica 2024年第2期37卷 341-360页

作者： Pei-Liang Bian Zhaowei Liu Hai Qing tiantang yu Department of Engineering Mechanics Hohai UniversityNanjing211100China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China

Scale effects play critical roles in the mechanical responses of *** isogeometric analysis was developed here to investigate the mechanical responses of an axially functionally graded *** Euler–Bernoulli beam model was utilized,and size effects in the structure were modeled with a stress-driven two-phase local/nonlocal integral *** governing equation of microstructures was given in an equivalent differential form with two additional constitutive boundary *** framework was verified and utilized to analyze the microbeam’s static and dynamic mechanical *** present work showed great potential for modeling various types of functionally graded microstructures.

关键词： Isogeometric analysis Size effect Functionally graded material Nonlocal theory Euler-Bernoulli beam

Analysis of Unsteady Heat Transfer Problems with Complex Geometries Using Isogeometric Boundary Element Method

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Computers, Materials & Continua 2020年第2期62卷 929-962页

作者： Weihua Fang Zhilin An tiantang yu Tinh Quoc Bui Nanjing Automation Institute of Water Conservancy and Hydrology Nanjing210012China Department of Engineering Mechanics Hohai UniversityNanjing211100China Institute for Research and Development Duy Tan UniversityDa Nang CityVietnam Department of Civil and Environmental Engineering Tokyo Institute of Technology2-12-1-W8-22OokayamaMeguro-kuTokyo 152-8552Japan

Numerical analysis of unsteady heat transfer problems with complex geometries by the isogeometric boundary element method(IGABEM)is *** IGABEM possesses many desirable merits and features,for instance,(a)exactly represented arbitrarily complex geometries,and higher-order continuity due to non-uniform rational B-splines(NURBS)shape functions;(b)using NURBS for both field approximation and geometric description;(c)directly utilizing geometry data from computer-aided design(CAD);and(d)only boundary *** formulation of IGABEM for unsteady heat transfer is *** domain discretization in terms of IGABEM for unsteady heat transfer is required as that in traditional *** internal values however are obtained with the analytical formula according to the values on the boundaries,and its computations are therefore mainly dependent on the discretization of the *** coordinates of internal control points are obtained with the coordinates of control points on the boundaries using Coons body interpolation *** developed approach is tested with several numerical examples from simple to complicated *** agreement is gained with reference solutions derived from either analytical or finite element methods.

关键词： Unsteady heat transfer BEM isogeometric analysis NURBS

Simulation of cohesive crack growth by a variable-node XFEM

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Frontiers of Structural and Civil Engineering 2020年第1期14卷 215-228页

作者： Weihua FANG Jiangfei WU tiantang yu Thanh-Tung NGUYEN Tinh Quoc BUI Nanjing Automation Institute of Water Conservancy and Hydrology Nanjing 210012China Department of Engineering Mechanics Hohai UniversityNanjing 211100China Laboratory of Solid Structures University of LuxembourgLuxembourg L-1359Luxembourg Institute for Research and Development Duy Tan UniversityDa Nang City 550000Vietnam Department of Civil and Environmental Engineering Tokyo Institute of TechnologyTokyo 152-8552Japan

A new computational approach that combines the extended finite element method associated with variable-node elements and cohesive zone model is *** using a new enriched technique based on sign function,the proposed model using 4-node quadrilateral elements can eliminate the blending element *** also allows modeling the equal stresses at both sides of the crack in the crack-tip as assumed in the cohesive model,and is able to simulate the arbitrary crack-tip *** multiscale mesh technique associated with variable-node elements and the arc-length method further improve the efficiency of the developed *** performance and accuracy of the present approach are illustrated through numerical experiments considering both mode-I and mixed-mode fracture in concrete.

关键词： extended finite element method cohesive zone model sign function crack propagation

Numerical modeling of concrete hydraulic fracturing with extended finite element method

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中国科学：技术科学 2010年第3期40卷 320-348页

作者： REN QingWen DONG yuWen yu tiantang Department of Engineering Mechanics Hohai University Nanjing 210098 China College of River and Ocean Engineering Chongqing Jiaotong University Chongqing 400074 China

The extended finite element method (XFEM) is a new numerical method for modeling *** about numerical modeling for concrete hydraulic fracturing by XFEM is *** building the virtual work principle of the fracture problem considering water pressure on the crack surface,the governing equations of XFEM for hydraulic fracture modeling are *** of the XFEM for hydraulic fracturing is ***,the method is verified by two examples and the advantages of the XFEM for hydraulic fracturing analysis are displayed.

关键词：有限元数字模型混凝土压力

Comparative Study on Deformation Prediction Models of Wuqiangxi Concrete Gravity Dam Based on Monitoring Data

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Computer Modeling in Engineering & Sciences 2022年第4期131卷 49-72页

作者： Songlin Yang Xingjin Han Chufeng Kuang Weihua Fang Jianfei Zhang tiantang yu Hunan Wuling Power Technology Corporation Ltd. Changsha410004China Wuling Power Corporation Ltd. Changsha410004China Nanjing Research Institute of Hydrology and Water Conservation Automation Ministry of Water ResourcesNanjing210012China Department of Engineering Mechanics Hohai UniversityNanjing211100China

The deformation prediction models of Wuqiangxi concrete gravity dam are developed,including two statistical models and a deep learning *** the statistical models,the reliable monitoring data are firstly determined with Lahitte criterion;then,the stepwise regression and partial least squares regression models for deformation prediction of concrete gravity dam are constructed in terms of the reliable monitoring data,and the factors of water pressure,temperature and time effect are considered in the models;finally,according to the monitoring data from 2006 to 2020 of five typical measuring points including J23(on dam section 24^(#)),J33(on dam section 4^(#)),J35(on dam section 8^(#)),J37(on dam section 12^(#)),and J39(on dam section 15^(#))located on the crest of Wuqiangxi concrete gravity dam,the settlement curves of the measuring points are obtained with the stepwise regression and partial least squares regression models.A deep learning model is developed based on long short-term memory(LSTM)recurrent neural *** the LSTM model,two LSTMlayers are used,the rectified linear unit function is adopted as the activation function,the input sequence length is 20,and the random search is *** monitoring data for the five typical measuring points from 2006 to 2017 are selected as the training set,and the monitoring data from 2018 to 2020 are taken as the test *** the results of case study,we can find that(1)the good fitting results can be obtained with the two statistical models;(2)the partial least squares regression algorithm can solve the model with high correlation factors and reasonably explain the factors;(3)the prediction accuracy of the LSTM model increases with increasing the amount of training *** the deformation prediction of concrete gravity dam,the LSTM model is suggested when there are sufficient training data,while the partial least squares regression method is suggested when the training data are insufficient.

关键词： Wuqiangxi concrete gravity dam deformation prediction stepwise regression model partial least squares regression model LSTM model