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CONTENTS
Volume 58, Number 3, May10 2016
 

Abstract
In the present work, a simple first-order shear deformation theory is developed and validated for a variety of numerical examples of the thermal buckling response of functionally graded sandwich plates with various boundary conditions. Contrary to the conventional first-order shear deformation theory, the present first-order shear deformation theory involves only four unknowns and has strong similarities with the classical plate theory in many aspects such as governing equations of motion, and stress resultant expressions. Material properties and thermal expansion coefficient of the sandwich plate faces are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are considered as uniform, linear and non-linear temperature rises within the thickness direction. The results reveal that the volume fraction index, loading type and functionally graded layers thickness have significant influence on the thermal buckling of functionally graded sandwich plates. Moreover, numerical results prove that the present simple first-order shear deformation theory can achieve the same accuracy of the existing conventional first-order shear deformation theory which has more number of unknowns.

Key Words
plate theory; thermal buckling; functionally graded plate; sandwich plate; volume fraction index

Address
Bachir Bouderba: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Mohammed Sid Ahmed Houari: Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics, Universite de Sidi Bel Abbes, Faculte de Technologie, BP 89 Cite Ben M\'hidi 22000 Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics, Universite de Sidi Bel Abbes, Faculte de Technologie, BP 89 Cite Ben M\'hidi 22000 Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia; Mathematics Department, Faculty of Science, University of Sohag, Egypt

Abstract
This study considers a functionally graded (FG) elastic layer resting on homogeneous elastic substrate under axisymmetric static loading. The shear modulus of the FG layer is assumed to vary in an exponential form through the thickness. In solution, the FG layer is approximated into a multilayered medium consisting of thin homogeneous sublayers. Stiffness matrices for a typical homogeneous isotropic elastic layer and a half-space are first obtained by solving the axisymmetric elasticity equations with the aid of Hankel\'s transform. Global stiffness matrix is, then, assembled by considering the continuity conditions at the interfaces. Numerical results for the displacements and the stresses are obtained and compared with those of the classical elasticity and the finite element solutions. According to the results of the study, the approach employed here is accurate and efficient for elasto-static problems of FGMs.

Key Words
stiffness matrix method; functionally graded material; layered media; elasticity; Hankel

Address
Muhittin Turan, Gokhan Adiyaman, Volkan Kahya and Ahmet Birinci: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
In this paper, we propose a method for taking into account uncertainties based on the projection on polynomial chaos. Due to the manufacturing and assembly errors, uncertainties in material and geometric properties, the system parameters including assembly defect, damping coefficients, bending stiffness and traction-compression stiffness are uncertain. The proposed method is used to determine the dynamic response of a one-stage spur gear system with uncertainty associated to gear system parameters. An analysis of the effect of these parameters on the one stage gear system dynamic behavior is then treated. The simulation results are obtained by the polynomial chaos method for dynamic analysis under uncertainty. The proposed method is an efficient probabilistic tool for uncertainty propagation. The polynomial chaos results are compared with Monte Carlo simulations.

Key Words
uncertainty; one-stage gear system; polynomial chaos; assembly defect, random variable; Monte Carlo simulation

Address
M. Beyaoui: Department of Mechanical Engineering, National School of Engineers of Sfax, BP 1173-3038 Sfax, Tunisia
A. Guerine: Department of Mechanical Engineering, National School of Engineers of Sfax, BP 1173-3038 Sfax, Tunisia; Department of Mechanical Engineering, INSA of Rouen, BP 08-76801 Saint Etienne du Rouvray, France
L. Walha: Department of Mechanical Engineering, National School of Engineers of Sfax, BP 1173-3038 Sfax, Tunisia
A. El Hami: Department of Mechanical Engineering, INSA of Rouen, BP 08-76801 Saint Etienne du Rouvray, France
T. Fakhfakh and M. Haddar: Department of Mechanical Engineering, National School of Engineers of Sfax, BP 1173-3038 Sfax, Tunisia

Abstract
Various vague and unstructured problems encountered the civil engineering/ designers that persuaded by their experiences. One of these problems is the structural failure of the reinforced concrete (RC) building determination. Typically, using the traditional Limit state method is time consuming and complex in designing structures that are optimized in terms of one/many parameters. Recent research has revealed the Artificial Neural Networks potentiality in solving various real life problems. Thus, the current work employed the Multilayer Perceptron Feed-Forward Network (MLP-FFN) classifier to tackle the problem of predicting structural failure of multistoried reinforced concrete buildings via detecting the failure possibility of the multistoried RC building structure in the future. In order to evaluate the proposed method performance, a database of 257 multistoried buildings RC structures has been constructed by professional engineers, from which 150 RC structures were used. From the structural design, fifteen features have been extracted, where nine features of them have been selected to perform the classification process. Various performance measures have been calculated to evaluate the proposed model. The experimental results established satisfactory performance of the proposed model.

Key Words
Reinforced Concrete (RC) structures; structural failure; Artificial Neural Network (ANN); Multilayer Perceptron Feed-Forward Network (MLP-FFN); scaled conjugate gradient algorithm; crossentropy

Address
Sirshendu Hore: Department of Computer Science&Engineering, Hooghly Engineering&Technology College Chinsurah, India
Sankhadeep Chatterjee: Department of Computer Science & Engineering, University of Calcutta, Kolkata, Iindia
Sarbartha Sarkar: Department of Civil Engineering, Hooghly Engineering & Technology College Chinsurah, India
Nilanjan Dey: Department of Information Technology, Techno India College of Technology, Kolkata, India
Amira S. Ashour: Department of Electronics and Electrical Communications Engineering, Faculty of Engineering, Tanta University, Egypt
Dana Balas-Timar: Faculty of Educational Sciences, Psychology and Social Sciences, Aurel Vlaicu University of Arad, Romania
Valentina E. Balas: Faculty of Engineering, Aurel Vlaicu University of Arad, Romania

Abstract
Various models have been proposed by several researchers for predicting the exterior RC beamcolumn joint shear strength. Most of these models were calibrated and verified with some limited experimental database. From the models it has been identified that the joint shear strength majorly depends on ten governing parameters. In the present paper, detailed investigation of twelve analytical models for predicting shear strength of exterior beam-column joint has been carried out. The study shows the effect of each governing parameter on joint shear strength predicted by various models. It has been observed that the consensus on effect of few of the governing parameters amongst the considered analytical models has not been attained. Moreover, the predicted joint strength by different models varies significantly. Further, the prediction of joint shear strength by these analytical models has also been compared with a set of 200 experimental results from the literature. It has been observed that none of the twelve models are capable of predicting joint shear strength with sufficient accuracy for the complete range of experimental results. The research community has to reconsider the effect of each parameters based on larger set of test results and new improved analytical models should be proposed.

Key Words
RC exterior beam-column joint; seismic behavior; shear strength; parametric analysis; experimental database

Address
Kanak Parate and Ratnesh Kumar: Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur, India

Abstract
The elastoplastic response of functionally graded material (FGM) beams resting on a nonlinear elastic foundation to an eccentric axial load is investigated by using the finite element method. The FGM is assumed to be formed from ceramic and metal phases with their volume fraction vary in the thickness direction by a power-law function. A bilinear elastoplastic behavior is assumed for the metallic phase, and the effective elastoplastic properties of the FGM are evaluated by Tamura-Tomota-Ozawa (TTO) model. Based on the classical beam theory, a nonlinear finite beam element taking the shift in the neutral axis position into account is formulated and employed in the investigation. An incremental-iterative procedure in combination with the arc-length control method is employed in computing the equilibrium paths of the beams. The validation of the formulated element is confirmed by comparing the equilibrium paths obtained by using the present element and the one available in the literature. The numerical results show that the elastoplastic post-buckling of the FGM beams is unstable, and the post-buckling strength is higher for the beams associated with a higher ceramic content. Different from homogeneous beams, yielding in the FGM beam occurs in the layer near the ceramic layer before in the layer near metal surface. A parametric study is carried out to highlight the effect of the material distribution, foundation support and eccentric ratio on the elastoplastic response of the beams.

Key Words
FGM beam; elastoplastic behavior; nonlinear elastic foundation; eccentric axial load; nonlinear finite element analysis

Address
Thanh-Huong Trinh: Department of Architecture, College of Engineering, Nihon University, Koriyama, Fukushima, 963-8642 Japan
Dinh-Kien Nguyen: Department of Solid Mechanics, Institute of Mechanics, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
Buntara S. Gan: Department of Architecture, College of Engineering, Nihon University, Koriyama, Fukushima, 963-8642 Japan
S. Alexandrov: Laboratory of Fracture Mechanics, Institute for Problems in Mechanics, Moscow 11926, Russia

Abstract
In this paper, the recently developed meta-heuristic algorithm called tug of war optimization is applied to optimal design of castellated beams. Two common types of laterally supported castellated beams are considered as design problems: beams with hexagonal openings and beams with circular openings. Here, castellated beams have been studied for two cases: beams without filled holes and beams with end-filled holes. Also, tug of war optimization algorithm is utilized for obtaining the solution of these design problems. For this purpose, the minimum cost is taken as the objective function, and some benchmark problems are solved from literature.

Key Words
meta-heuristic algorithm; tug of war optimization; optimal design; hexagonal opening; cellular opening

Address
A. Kaveh and F. Shokohi: Centre of Excellence for Fundamental Studies in Structural Engineering, Iran University of Science and Technology, Narmak, Tehran, P.O. Box 16846-13114, Iran

Abstract
In this paper an efficient approach is introduced for design and analysis of double-layer grids including both geometrical and material nonlinearities, while the results are compared with those considering material nonlinearity. Optimum design procedure based on Enhanced Colliding Bodies Optimization method (ECBO) is applied to optimal design of two commonly used configurations of doublelayer grids. Two ranges of spans as small and big sizes with certain bays of equal length in two directions are considered for each type of square grids. ECBO algorithm obtains minimum weight grid through appropriate selection of tube sections available in AISC Load and Resistance Factor Design (LRFD). Strength constraints of AISC-LRFD specifications and displacement constraints are imposed on these grids.

Key Words
double-layer grids; nonlinear behavior; incremental nonlinear analysis; collapse; enhanced colliding bodies optimization

Address
A. Kaveh: Center of Excellence For Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science and Technology, Narmak, Tehran -16, Iran
M. Moradveisi: Road, Housing and Urban Development Research Center, Tehran P.O. Box 13145-1696, Iran

Abstract
FRP-concrete interfacial mechanical properties determine the strengthening effect of RC beams strengthened with FRP. In this paper, the model experiments were carried out with eight specimens to study the failure modes and the strengthening effect of RC beams strengthened with FRP. Then a theoretical model based on interfacial performances was proposed and interfacial mechanical behaviors were studied. Finite element analysis confirmed the theoretical results. The results showed that RC beams strengthened with FRP had three loading stages and that the FRP strengthening effects were mainly exerted in the Stage III after the yielding of steel bars, including the improvement of the bearing capacity, the decreased ultimate deformation due to the sudden failure of FRP and the improvement of stiffness in this stage. The mechanical formulae of the interfacial shear stress and FRP stress were established and the key influence factors included FRP length, interfacial bond-slip parameter, FRP thickness, etc. According to the theoretical analysis and experimental data, the calculation methods of interfacial shear stress at FRP end and FRP strain at midspan were proposed. When FRP bonding length was shorter, interfacial shear stress at FRP end was larger that led to concrete cover peeling failure. When FRP was longer, FRP reached the ultimate strain and the fracture failure of FRP occurred. The theoretical results were well consistent with the experimental data.

Key Words
interfacial mechanical behaviors; RC beams; FRP; model experiment; theoretical model; finite element analysis

Address
Jiangdong Deng: College of Civil Engineering, Guangzhou University, Guangzhou 510006, China
Airong Liu: Guangzhou University-Tamkang University Joint Research Center for Engineering Structure Disaster Prevention and Control, Guangzhou University, Guangzhou 510006, ChinaCollege of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China
Peiyan Huang and Xiaohong:

Abstract
This paper presents an optimization process using Harmony Search Algorithm for minimum weight of steel space frames under earthquake effects according to Turkish Earthquake Code (2007) specifications. The optimum designs are carried out by selecting suitable sections from a specified list including W profiles taken from American Institute of Steel Construction (AISC). The stress constraints obeying AISC- Load and Resistance Factor Design (LRFD) specifications, lateral displacement constraints and geometric constraints are considered in the optimum designs. A computer program is coded in MATLAB for the purpose to incorporate with SAP2000 OAPI (Open Application Programming Interface) to perform structural analysis of the frames under earthquake loads. Three different steel space frames are carried out for four different seismic earthquake zones defined in Turkish Earthquake Code (2007). Results obtained from the examples show the applicability and robustness of the method.

Key Words
harmony search algorithm; optimum design; steel space frames; earthquake effect

Address
Musa Artar: Department of Civil Engineering, Bayburt University, Bayburt 69000, Turkey


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