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CONTENTS
Volume 13, Number 1, January 2014
 

Abstract
The present study deals with two dimensional electro-elastic analysis of a functionally graded piezoelectric (FGP) cylinder under internal pressure. Energy method and first order shear deformation theory (FSDT) are employed for this purpose. All mechanical and electrical properties except Poisson ratio are considered as a power function along the radial direction. The cylinder is subjected to uniform internal pressure. By supposing two dimensional displacement and electric potential fields along the radial and axial direction, the governing differential equations can be derived in terms of unknown electrical and mechanical functions. Homogeneous solution can be obtained by imposing the appropriate mechanical and electrical boundary conditions. This proposed solution has capability to solve the cylinder structure with arbitrary boundary conditions. The previous solutions have been proposed for the problem with simple boundary conditions (simply supported cylinder) by using the routine functions such as trigonometric functions. The axial distribution of the axial displacement, radial displacement and electric potential of the cylinder can be presented as the important results of this paper for various non homogeneous indexes. This paper evaluates the effect of a local support on the distribution of mechanical and electrical components. This investigation indicates that a support has important influence on the distribution of mechanical and electrical components rather than a cylinder with ignoring the effect of the supports. Obtained results using present method at regions that are adequate far from two ends of the cylinder can be compared with previous results (plane elasticity and one dimensional first order shear deformation theories).

Key Words
piezoelectric; pressure; cylindrical shell; first order shear deformation theory; energy method

Address
M. Arefi:Department of Solid Mechanic, Faculty of Mechanical Engineering, University of Kashan,
Kashan 87317-51167, Iran
G.H. Rahimi: Department of Mechanical engineering, Tarbiat Modares University, Tehran 14115-143, Iran

Abstract
The axisymmetric dynamic instability of polar orthotropic sandwich annular plate combined with electrorheological (ER) fluid core layer and constraining layer are studied in this paper. And, the ER core layer and constraining layer are used to improve the stability of the annular plate system. The boundaries of instability regions for the polar orthotropic sandwich annular plate system are obtained by discrete layer annular finite element and the harmonic balance method. The rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be controlled by applying different electric field strength. Thus, the damping characteristics of the sandwich system are more effective when the electric field is applied on the sandwich structure. Additionally, variations of the instability regions for the polar orthotropic sandwich annular plate with different applying electric field strength, thickness of ER layer and some designed parameters are investigated and discussed in this study.

Key Words
dynamic instability; polar orthotropic; electrorheological; annular plate; discrete layer annular finite element

Address
Jia-Yi Yeh: Department of Information Management, Chung Hwa University of Medical Technology, 89, Wen-Hwa 1st ST. Jen-Te Hsiang, Tainan County 717, Taiwan, R.O.C.

Abstract
Optical fiber Brillouin sensor in a coil winding setup is proposed in this paper to measure the expansion deformation of a concrete column with a central rebar subjected to accelerated corrosion. The optical sensor monitored the whole dynamic corrosion process from initial deformation to final cracking. Experimental results show that Brillouin Optical Time Domain Reflectometer (BOTDR) can accurately measure the strain values and identify the crack locations of the simulated reinforced concrete (RC) column. A theoretical model is used to calculate the RC corrosion expansive pressure and crack length. The results indicate that the measured strain and cracking history revealed the development of the steel bar corrosion inside the simulated RC column.

Key Words
rebar corrosion; expansion pressure; BOTDR; optical fiber; distributed sensing monitoring

Address
Yijie Sun, Bin Shi, Honghu Zhu, Dan Zhang and Yi Lu:School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
Shen-en Chen:Department of Civil and Environmental Engineering, University of North Carolina
Charlotte, NC 28223, USA

Abstract
The present work pays emphasis on investigating the effect of different types of debonding on the bending behaviour of active sandwich beam, consisting of both extension and shear actuators. An active sandwich beam finite element is formulated by using Timoshenko\'s beam theory, characterized by first order shear deformation for the core and Euler-Bernoulli\'s beam theory for the top and bottom faces. The problem of debondings of extension actuator and face are dealt with by employing four-region model for inner debonding and three-region model for the edge debonding respectively. Displacement based continuity conditions are enforced at the interfaces of different regions using penalty method. Firstly, piezoelectric actuation of healthy sandwich beam is assessed through deflection analysis. Then the effect of actuators\'debondings with different boundary conditions on bending behavior is computationally evaluated and experimentally clamped-free case is validated. The results generated will be useful to address the damage tolerant design procedures for smart sandwich beam structures with structural control and health monitoring applications.

Key Words
sandwich beam; piezoelectric actuator; extension actuation mechanism (EAM); shear actuation mechanism (SAM); hybrid actuation mechanism (HAM); debonding

Address
Venkata Rao:Department of Mechanical Engineering, B.M.S Evening College of Engg., Bangalore- 560019, India
S. Raja: Structural Technologies Division, CSIR-National Aerospace Laboratories, Bangalore-560017, India
T. Munikenche Gowda: Principal, S.J.C. institute of Technology, Chickballapur-562101, India

Abstract
This paper presents the elastic buckling of smart lightweight column structures integrated with a pair of surface piezoelectric layers using artificial intelligence. The finite element modeling of Smart lightweight columns is found using ANSYS(R) software. Then, the first buckling load of the structure is calculated using eigenvalue buckling analysis. To determine the accuracy of the present finite element analysis, a compression study is carried out with literature. Later, parametric studies for length variations, width, and thickness of the elastic core and of the piezoelectric outer layers are performed and the associated buckling load data sets for artificial intelligence are gathered. Finally, the application of soft computing-based methods including artificial neural network (ANN), fuzzy inference system (FIS), and adaptive neuro fuzzy inference system (ANFIS) were carried out. A comparative study is then made between the mentioned soft computing methods and the performance of the models is evaluated using statistic measurements. The comparison of the results reveal that, the ANFIS model with Gaussian membership function provides high accuracy on the prediction of the buckling load in smart lightweight columns, providing better predictions compared to other methods. However, the results obtained from the ANN model using the feed-forward algorithm are also accurate and reliable.

Key Words
smart columns; buckling load; artificial neural network; fuzzy inference system; adaptive neuro fuzzy inference system; ANSYS

Address
Yaser Shahbazi:Architecture and Urbanism Department, Tabriz Islamic Art University, Tabriz, Iran
Ehsan Delavari and Mohammad Reza Chenaghlou:Department of Civil Engineering, Sahand University of Technology, Tabriz, Iran

Abstract
The goal of any Model Order Reduction (MOR) technique is to build a model of order lower than the one of the real model, so that the computational effort is reduced, and the ability to estimate the input-output mapping of the original system is preserved in an important region of the input space. Actually, since only a subset of the input space is of interest, the matching is required only in this subset of the input space. In this contribution, the consequences on the achieved accuracy of adopting different reduction technique patterns is discussed mainly with reference to a linear case study.

Key Words
dynamic analysis; model order reduction (MOR); numerical model; truncation

Address
Sara Casciati:Department DICA, University of Catania, Piazza Federico di Svevia, 96100 Siracusa, Italy
Lucia Faravelli: Department DICAR, University of Pavia, Via Ferrata 1, 27100 Pavia, Italy

Abstract
Based on the Reissner mixed variational theorem (RMVT), finite rectangular layer methods (FRLMs) are developed for the three-dimensional (3D) linear buckling analysis of simply-supported, fiber-reinforced composite material (FRCM) and functionally graded material (FGM) sandwich plates subjected to bi-axial compressive loads. In this work, the material properties of the FGM layers are assumed to obey the power-law distributions of the volume fractions of the constituents through the thickness, and the plate is divided into a number of finite rectangular layers, in which the trigonometric functions and Lagrange polynomials are used to interpolate the in- and out-of-plane variations of the field variables of each individual layer, respectively, and an h-refinement process is adopted to yield the convergent solutions. The accuracy and convergence of the RMVT-based FRLMs with various orders used for expansions of each field variables through the thickness are assessed by comparing their solutions with the exact 3D and accurate two-dimensional ones available in the literature.

Key Words
Reissner

Address
Chih-Ping Wuand Wei-Lun Liu: Department of Civil Engineering, National Cheng Kung University, Tainan 70101, Taiwan, ROC

Abstract
Servohydraulic shaking tables are being increasingly used in the field of earthquake engineering. They play a critical role in the advancement of the research state and remain one of the valuable tools for seismic testing. Recently, the National Earthquake Engineering Research Center, CGS, has acquired a 6.1m x 6.1 m shaking table system which has a six degree-of-freedom testing capability. The maximum specimen mass that can be tested on the shaking table is 60 t. This facility is designed specially for testing a complete civil engineering structures, substructures and structural elements up to collapse or ultimate limit states. It can also be used for qualification testing of industrial equipments. The current paper presents the main findings of the experimental shake-down characterization testing of the CGS shaking table. The test program carried out in this study included random white noise and harmonic tests. These tests were performed along each of the six degrees of freedom, three translations and three rotations. This investigation provides fundamental parameters that are required and essential while elaborating a realistic model of the CGS shaking table. Also presented in this paper, is the numerical model of the shaking table that was established and validated.

Key Words
servohydralic shaking table; parameter estimation; identification; random and cyclic testing

Address
Abdelhalim Airouche and Hassan Aknouche:National Earthquake Engineering Research Center, CGS, Rue Kaddour Rahim Prolongée Bp 252 H-Dey Alger, Algeria;
University of Bab Ezzouar (USTHB), FGC/ Built Environment Res. Lab. (LBE) BP 32 El Alia, Bab Ezzouar, Alger 16111, Algeria
Hakim Bechtoula: National Earthquake Engineering Research Center, CGS, Rue Kaddour Rahim Prolongée Bp 252 H-Dey Alger, Algeria
Bradford K.Thoen:MTS Systems Corporation, 14000 Technology Drive, Eden Prairie, MN 55344, USA
Djillali Benouar:University of Bab Ezzouar (USTHB), FGC/ Built Environment Res. Lab. (LBE) BP 32 El Alia, Bab Ezzouar, Alger 16111, Algeria

Abstract
Various monitoring techniques are now available for structural health monitoring and Acoustic Emission (AE) is one of them. One of the major advantages of the AE technique is its capability to locate active cracks in structural members. AE crack locating approaches are affected by the signal attenuation and dispersion of elastic waves due to inhomogeneity and geometry of reinforced concrete (RC) members. In this paper, a novel technique is described based on signal processing and sensor arrangement to process multisensory AE data generated by the onset and propagation of cracks and is validated with experimental results from an in-situ load test. Considering the sources of uncertainty in the AE crack location process, a methodology is proposed to capture and locate events generated by cracks. In particular, the relationship between AE events and load is analyzed, and the feasibility of using the AE technique to evaluate the cracking behavior of two RC slab strips during loading to failure is studied.

Key Words
acoustic emission; crack location; nondestructive evaluation; reinforced concrete; sensor configuration

Address
Tala Shokri and Antonio Nanni: College of Engineering (Civil), University of Miami, Coral Gables, USA


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