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Simulation of fracture in plain concrete modeled as a composite material
Thanh T. Bui,Mario M. Attard 한국계산역학회 2005 Computers and Concrete, An International Journal Vol.2 No.6
A composite model is used to represent the heterogeneity of plain concrete consisting of coarse aggregates, mortar matrix and the mortar-aggregate interface. The composite elements of plain concrete are modeled using triangular finite element units which have six interface nodes along the sides. Fracture is captured through a constitutive single branch softening-fracture law at the interface nodes, which bounds the elastic domain inside each triangular unit. The inelastic displacement at an interface node represents the crack opening or sliding displacement and is conjugate to the internodal force. The path-dependent softening behaviour is developed within a quasi-prescribed displacement control formulation. The crack profile is restricted to the interface boundaries of the defined mesh. No re-meshing is carried out. Solutions to the rate formulation are obtained using a mathematical programming procedure in the form of a linear complementary problem. An event by event solution strategy is adopted to eliminate solutions with simultaneous formation of softening zones in symmetric problems. The composite plain concrete model is compared to experimental results for the tensile crack growth in a Brazilian test and three-point bending tests on different sized specimens. The model is also used to simulate wedge-type shear-compression failure directly under the loading platen of a Brazilian test.
Bui V. Hau,김윤섭,Ngo X. Thanh,Tran T. Hai,이기욱 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.4
The depositional and metamorphic ages, and provenances of metasedimentary rocks from the Nam Co Complex in the Son La area, Song Ma Suture Zone, northwestern Vietnam, were investigated in order to reveal the convergent tectonic history between the Indochina and South China cratons. This complex is structurally characterized by an antiformal metamorphic core consisting of two distinct metamorphic zones: inner garnet and outer biotite zones. The U-Pb isotopic dating on detrital zircon from metasandstones of the Nam Co Complex yielded major population (> 50%) around ~850 Ma with minor population scattered between 1.2 to 3.0 Ga. The age spectra as well as the morphologies, internal structures and geochemical features of detrital zircon are accounted for by magmatic activities prevalent at the convergent plate margin during the Neoproterozoic. In contrast, the UTh-Pb isotopic compositions of monazite from a garnet-zone schist defined a common Pb mixing line with the lower intercept age of 234 ± 10 Ma (2σ) reflecting the Indosinian metamorphic event. The U-Pb age distribution pattern of detrital zircon in the Nam Co Complex is compatible with that of the South China craton rather than that of the Indochina craton. In summary, sedimentary protoliths of the Nam Co Complex were deposited in a convergent-related basin along the southwestern margin of the South China craton during the Neoproterozoic, and then was finally amalgamated to the Indochina craton via the southerly subduction of South China craton during the Indosinian orogeny.
Solid State Dye-Sensitized Solar Cells Based on Polymeric Ionic Liquid with Free Imidazolium Cation
Thanh-Tuan Bui,Tarik Matrab,Vincent Woehling,Justine Longuet,Cédric Plesse,Giao T.M. Nguyen,Frédéric Vidal,Fabrice Goubard 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1
A polymeric ionic liquid issued from an ionic liquid monomer composed of a methacrylate polymerizable group, a polar tri(ethylene oxide) spacer, a trifluoromethane sulfonic anion and a free imidazolium cation was employed as a solid electrolyte for dye-sensitized solar cells. The simple device configuration based on dip-coated nanoporous TiO2 electrode sensitized by N3 ruthenium-based dye gave the conversion efficiency of up to 1.74% under AM 1.5 simulated solar light illumination. Effect of TiO2 porous film thickness on overall energy conversion efficiency was discussed. It has been found that the most appropriate thickness for the polymeric ionic liquid based electrolyte dye sensitized solar cell is around 7 μm.
An efficient hybrid TLBO-PSO-ANN for fast damage identification in steel beam structures using IGA
S. Khatir,T. Khatir,D. Boutchicha,C. Le Thanh,H. Tran-Ngoc,T.Q. Bui,R. Capozucca,M. Abdel Wahab 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.5
The existence of damages in structures causes changes in the physical properties by reducing the modal parameters. In this paper, we develop a two-stages approach based on normalized Modal Strain Energy Damage Indicator (<i>nMSEDI</i>) for quick applications to predict the location of damage. A two-dimensional IsoGeometric Analysis (2D-IGA), Machine Learning Algorithm (MLA) and optimization techniques are combined to create a new tool. In the first stage, we introduce a modified damage identification technique based on frequencies using <i>nMSEDI</i> to locate the potential of damaged elements. In the second stage, after eliminating the healthy elements, the damage index values from <i>nMSEDI</i> are considered as input in the damage quantification algorithm. The hybrid of Teaching-Learning-Based Optimization (TLBO) with Artificial Neural Network (ANN) and Particle Swarm Optimization (PSO) are used along with nMSEDI. The objective of TLBO is to estimate the parameters of PSO-ANN to find a good training based on actual damage and estimated damage. The IGA model is updated using experimental results based on stiffness and mass matrix using the difference between calculated and measured frequencies as objective function. The feasibility and efficiency of nMSEDI-PSO-ANN after finding the best parameters by TLBO are demonstrated through the comparison with nMSEDI-IGA for different scenarios. The result of the analyses indicates that the proposed approach can be used to determine correctly the severity of damage in beam structures.
Damage detection in Ca-Non Bridge using transmissibility and artificial neural networks
Duong H. Nguyen,Thanh T. Bui,Guido De Roeck,Magd Abdel Wahab 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.2
This paper deals with damage detection in a girder bridge using transmissibility functions as input data to ArtificialNeural Networks (ANNs). The original contribution in this work is that these two novel methods are combined to detect damage ina bridge. The damage was simulated in a real bridge in Vietnam, i.e. Ca-Non Bridge. Finite Element Method (FEM) of this bridgewas used to show the reliability of the proposed technique. The vibration responses at some points of the bridge under a movingtruck are simulated and used to calculate the transmissibility functions. These functions are then used as input data to train theANNs, in which the target is the location and the severity of the damage in the bridge. After training successfully, the network canbe used to assess the damage. Although simulated responses data are used in this paper, the practical application of the technique toreal bridge data is potentially high.
Comparison of various image fusion methods for impervious surface classification from VNREDSat-1
Hung V. Luu,Manh V. Pham,Chuc D. Man,Hung Q. Bui,Thanh T.N. Nguyen 국제문화기술진흥원 2016 International Journal of Advanced Culture Technolo Vol.4 No.2
Impervious surfaces are important indicators for urban development monitoring. Accurate mapping of urban impervious surfaces with observational satellites, such as VNREDSat-1, remains challenging due to the spectral diversity not captured by an individual PAN image. In this article, five multi-resolution image fusion techniques were compared for the task of classifting urban impervious surfaces. The result shows that for VNREDSat-1 dataset, UNB and Wavelet tranformation methods are the best techniques in reserving spatial and spectral information of original MS image, respectively. However, the UNB technique gives the best results when it comes to impervious surface classification, especially in the case of shadow areas included in non-impervious surface group.
Tran N. Hoa,S. Khatir,G. De Roeck,Nguyen N. Long,Bui T. Thanh,M. Abdel Wahab 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.4
This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.
Comparison of various image fusion methods for impervious surface classification from VNREDSat-1
Luu, Hung V.,Pham, Manh V.,Man, Chuc D.,Bui, Hung Q.,Nguyen, Thanh T.N. The International Promotion Agency of Culture Tech 2016 International Journal of Advanced Culture Technolo Vol.4 No.2
Impervious surfaces are important indicators for urban development monitoring. Accurate mapping of urban impervious surfaces with observational satellites, such as VNREDSat-1, remains challenging due to the spectral diversity not captured by an individual PAN image. In this article, five multi-resolution image fusion techniques were compared for the task of classifting urban impervious surfaces. The result shows that for VNREDSat-1 dataset, UNB and Wavelet tranformation methods are the best techniques in reserving spatial and spectral information of original MS image, respectively. However, the UNB technique gives the best results when it comes to impervious surface classification, especially in the case of shadow areas included in non-impervious surface group.