Time filter

Source Type

Truong B.T.,INSA Lyon | Bui T.T.,INSA Lyon | Limam A.,INSA Lyon | Si Larbi A.,National School of Engineering, Saint-Etienne | And 2 more authors.
Composite Structures | Year: 2017

Reinforcement and repair of reinforced concrete structures is often more economical and sustainable (less cement consumption, less CO2 production) than reconstruction. Currently, the solution of reinforcement/repair by carbon-epoxy materials applied to outer surfaces of the structures is routinely used. However, these composites have limitations in terms of cost, fire resistance and sustainable development criteria. The textile reinforced concrete (TRC) mineral-based composite is envisaged as an alternative solution that can solve, at least partially, the above drawbacks. This work aims to experimentally assess contributions of the strengthening/repair of slender reinforced concrete beams subjected to bending by applying the TRC composite. In the first approach, the use of TRC composites in the case of the repair/strengthening of tank shells will be evaluated on the basis of slender beams. Twelve reinforced concrete “beams” are tested for quasi-static monotonic loading by bending tests over four points among 10 beams that have been reinforced/repaired by composite materials. Several parameters including two different modes of curing conditions (28 days immersion in water at 20 °C; 28 days left in air at 20 °C, 50 RH), and two different types of configurations of the beams (with and without pre-cracking) have been considered. This study highlights the mechanical performance of TRC in strengthening/repair of the reinforced concrete beams by analysing the changes in global behaviour (e.g., load/deflection, failure mode, flexural rigidity) and local behaviour (e.g., deformation of steel, pattern cracking, the crack opening). Further evaluation of the local behaviour of TRC should be conducted to address the damage mechanism by multi-cracking of the material and changing the opening of the crack located on the face of the composite. © 2017 Elsevier Ltd


Pham B.T.,Gujarat Technological University | Pham B.T.,University of Transport Technology | Tien Bui D.,Telemark University College | Prakash I.,Institute of Space Technology | Dholakia M.B.,Gujarat Technological University
Catena | Year: 2017

The main objective of this study is to evaluate and compare the performance of landslide models using machine learning ensemble technique for landslide susceptibility assessment. This technique is a combination of ensemble methods (AdaBoost, Bagging, Dagging, MultiBoost, Rotation Forest, and Random SubSpace) and the base classifier of Multiple Perceptron Neural Networks (MLP Neural Nets). Ensemble techniques have been widely applied in other fields; however, their application is still rare in the assessment of landslide problems. Meanwhile, MLP Neural Nets, which is known as an artificial neural network, has been applied widely and efficiently in landslide problems. In the present study, landslide models of part Himalayan area (India) have been constructed and validated. For the evaluation and comparison of these models, receiver operating characteristic curve and Chi Square test methods have been applied. Overall, all landslide models performed well in landslide susuceptibility assessment but the performance of the MultiBoost model is the highest (AUC = 0.886), followed by Dagging model (AUC = 0.885), the Rotation Forest model (AUC = 0.882), the Bagging and Random SubSpace models (AUC = 0.881), and the AdaBoost model (AUC = 0.876), respectively. Moreover, machine learning ensemble models have improved significantly the performance of the base classifier of MLP Neural Nets (AUC = 0.874). Analysis of results indicates that landslide models using machine learning ensemble frameworks are promising methods which can be used as alternatives of individual base classifiers for landslide susceptibility assessment of other prone areas. © 2016 Elsevier B.V.


Bich D.H.,Vietnam National University, Hanoi | Dung D.V.,Vietnam National University, Hanoi | Nam V.H.,University of Transport Technology
Composite Structures | Year: 2012

Based on the classical shell theory with the geometrical nonlinearity in von Karman-Donnell sense and the smeared stiffeners technique, the governing equations of motion of eccentrically stiffened functionally graded cylindrical panels with geometrically imperfections are derived in this paper. The characteristics of free vibration and nonlinear responses are investigated. The nonlinear dynamic buckling of cylindrical panel acted on by axial loading is considered. The nonlinear dynamic critical buckling loads are found according to the criterion suggested by Budiansky-Roth. Some numerical results are given and compared with the ones of other authors. © 2012 Elsevier Ltd.


Bich D.H.,Vietnam National University, Hanoi | Phuong N.T.,University of Transport Technology | Tung H.V.,Hanoi Architectural University
Composite Structures | Year: 2012

This paper presents an analytical approach to investigate the linear buckling of truncated conical panels made of functionally graded materials and subjected to axial compression, external pressure and the combination of these loads. Material properties are assumed to be temperature-independent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of constituents. Equilibrium and linear stability equations in terms of displacement components for conical panels are derived by using the classical thin shell theory. Approximate analytical solutions are assumed to satisfy simply supported boundary conditions and Galerkin method is applied to obtain closed-form relations of bifurcation type buckling loads. An analysis is carried out to show the effects of material and geometrical properties and combination of loads on the linear stability of conical panels. © 2011 Elsevier Ltd.


Bich D.H.,Vietnam National University, Hanoi | Dung D.V.,Vietnam National University, Hanoi | Nam V.H.,University of Transport Technology
Composite Structures | Year: 2013

This paper presents a semi-analytical approach to investigate the nonlinear dynamic of imperfect eccentrically stiffened functionally graded shallow shells taking into account the damping subjected to mechanical loads. The functionally graded shallow shells are simply supported at edges and are reinforced by transversal and longitudinal stiffeners on internal or external surface. The formulation is based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense and the smeared stiffeners technique. By Galerkin method, the equations of motion of eccentrically stiffened imperfect functionally graded shallow shells are derived. Dynamic responses are obtained by solving the equation of motion by the Runge-Kutta method. The nonlinear critical dynamic buckling loads are found according to the Budiansky-Roth criterion. Results of dynamic analysis show the effect of stiffeners, damping, pre-loaded compressions, material and geometric parameters on the dynamical behavior of these structures. © 2012 Elsevier Ltd.


Huy Bich D.,Vietnam National University, Hanoi | Van Dung D.,Vietnam National University, Hanoi | Nam V.H.,University of Transport Technology | Thi Phuong N.,University of Transport Technology
International Journal of Mechanical Sciences | Year: 2013

An analytical approach is presented to investigate the nonlinear static and dynamic buckling of imperfect eccentrically stiffened functionally graded thin circular cylindrical shells subjected to axial compression. Based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense, initial geometrical imperfection and the smeared stiffeners technique, the governing equations of motion of eccentrically stiffened functionally graded circular cylindrical shells are derived. The functionally graded cylindrical shells with simply supported edges are reinforced by ring and stringer stiffeners system on internal and (or) external surface. The resulting equations are solved by the Galerkin procedure to obtain the explicit expression of static critical buckling load, post-buckling load-deflection curve and nonlinear dynamic motion equation. The nonlinear dynamic responses are found by using fourth-order Runge-Kutta method. The dynamic critical buckling loads of shells under step loading of infinite duration are found corresponding to the load value of sudden jump in the average deflection and those of shells under linear-time compression are investigated according to Budiansky-Roth criterion. The obtained results show the effects of stiffeners and input factors on the static and dynamic buckling behavior of these structures. © 2013 Elsevier Ltd.


Dung D.V.,Vietnam National University, Hanoi | Nam V.H.,University of Transport Technology
European Journal of Mechanics, A/Solids | Year: 2014

A semi-analytical approach eccentrically stiffened functionally graded circular cylindrical shells surrounded by an elastic medium subjected to external pressure is presented The elastic medium is assumed as two-parameter elastic foundation model proposed by Pasternak. Based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense, the smeared stiffeners technique and Galerkin method, this paper deals the nonlinear dynamic problem. The approximate three-term solution of deflection shape is chosen and the frequency-amplitude relation of nonlinear vibration is obtained in explicit form. The nonlinear dynamic responses are analyzed by using fourth order Runge-Kutta method and the nonlinear dynamic buckling behavior of stiffened functionally graded shells is investigated according to Budiansky-Roth criterion. Results are given to evaluate effects of stiffener, elastic foundation and input factors on the frequency-amplitude curves, natural frequencies, nonlinear responses and nonlinear dynamic buckling loads of functionally graded cylindrical shells. © 2014 Elsevier Masson SAS. All rights reserved.


Pham B.T.,Gujarat Technological University | Pham B.T.,University of Transport Technology | Pradhan B.,University Putra Malaysia | Tien Bui D.,Telemark University College | And 2 more authors.
Environmental Modelling and Software | Year: 2016

Landslide susceptibility assessment of Uttarakhand area of India has been done by applying five machine learning methods namely Support Vector Machines (SVM), Logistic Regression (LR), Fisher's Linear Discriminant Analysis (FLDA), Bayesian Network (BN), and Naïve Bayes (NB). Performance of these methods has been evaluated using the ROC curve and statistical index based methods. Analysis and comparison of the results show that all five landslide models performed well for landslide susceptibility assessment (AUC = 0.910–0.950). However, it has been observed that the SVM model (AUC = 0.950) has the best performance in comparison to other landslide models, followed by the LR model (AUC = 0.922), the FLDA model (AUC = 0.921), the BN model (AUC = 0.915), and the NB model (AUC = 0.910), respectively. © 2016 Elsevier Ltd


Tien Bui D.,Telemark University College | Tien Bui D.,Hanoi University of Mining and Geology | Pham B.T.,Gujarat Technological University | Pham B.T.,University of Transport Technology | And 2 more authors.
International Journal of Digital Earth | Year: 2016

This study represents a hybrid intelligence approach based on the differential evolution optimization and Least-Squares Support Vector Machines for shallow landslide prediction, named as DE–LSSVMSLP. The LSSVM is used to establish a landslide prediction model whereas the DE is adopted to search the optimal tuning parameters of the LSSVM model. In this research, a GIS database with 129 historical landslide records in the Quy Hop area (Central Vietnam) has been collected to establish the hybrid model. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to assess the performance of the newly constructed model. Experimental results show that the proposed model has high performances with approximately 82% of AUCs on both training and validating datasets. The model’s results were compared with those obtained from other methods, Support Vector Machines, Multilayer Perceptron Neural Networks, and J48 Decision Trees. The result comparison demonstrates that the DE–LSSVMSLP deems best suited for the dataset at hand; therefore, the proposed model can be a promising tool for spatial prediction of rainfall-induced shallow landslides for the study area. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Nguyen Q.-H.,INSA Rennes | Hjiaj M.,INSA Rennes | Lai V.-A.,University of Transport Technology
Finite Elements in Analysis and Design | Year: 2014

This paper presents a novel finite element model for the fully material and geometrical nonlinear analysis of shear-deformable two-layer composite planar beam/column members with interlayer slips. We adopt the co-rotational approach where the motion of the element is decomposed into two parts: a rigid body motion which defines a local co-ordinate system and a small deformational motion of the element relative to this local co-ordinate system. The main advantage of this approach is that the transformation matrices relating local and global quantities are independent from the choice of the geometrical linear local element. The effect of transverse shear deformation of the layers is taken into account by assuming that each layer behaves as a Timoshenko beam element. The layers are assumed to be continuously connected and partial interaction is considered by adopting a continuous relationship between the interface shear flow and the corresponding slip. In order to avoid curvature and the shear locking phenomena, the local linear element is derived from the force-based formulation. The present model provides an efficient tool for the elastoplastic buckling analysis of two-layer shear deformable beam/column with arbitrary support and loading conditions. Finally, two numerical applications are presented in order to assess the performance of the proposed formulation. © 2014 Elsevier B.V.

Loading University of Transport Technology collaborators
Loading University of Transport Technology collaborators