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Volume 25, Number 2, October10 2017

In this paper, an exact analytical solution for simply supported sandwich plate which considers the permeation effect of adhesives is presented. The permeation layer is described as functionally graded material (FGM), the elastic modulus of which is assumed to be graded along the thickness following the exponential law. Based on the exact three-dimensional (3-D) elasticity theory, the solution of stresses and displacements for each layer is derived. By means of the recursive matrix method, the solution can be efficiently obtained for plates with many layers. The present solution obtained can be used as a benchmark to access other simplified solutions. The comparison study indicates that the finite element (FE) solution is close to the present one when the FGM layer in the FE model is divided into a series of homogeneous layers. However, the present method is more efficient than the FE method, with which the mesh division and computation are time-consuming. Moreover, the solution based on Kirchhoff-Love plate theory is greatly different from the present solution for thick plates. The influence of the thickness of the permeation layer on the stress and displacement fields of the sandwich plate is discussed in detail. It is indicated that the permeation layer can effectively relieve the discontinuity stress at the interface.

Key Words
sandwich plate; permeation effect; functionally graded material; elasticity solution; recursive matrix method

College of Civil Engineering, Nanjing Tech University, 211800 Nanjing, China.

This paper presents an investigation into the magneto-thermo-mechanical vibration and damping of a viscoelastic functionally graded-carbon nanotubes (FG-CNTs)-reinforced curved microbeam based on Timoshenko beam and strain gradient theories. The structure is surrounded by a viscoelastic medium which is simulated with spring, damper and shear elements. The effective temperature-dependent material properties of the CNTs-reinforced composite beam are obtained using the extended rule of mixture. The structure is assumed to be subjected to a longitudinal magnetic field. The governing equations of motion are derived using Hamilton's principle and solved by employing differential quadrature method (DQM). The effect of various parameter like volume percent and distribution type of CNTs, temperature change, magnetic field, boundary conditions, material length scale parameter, central angle, viscoelastic medium and structural damping on the vibration and damping behaviors of the nanocomposite curved microbeam is examined. The results show that with increasing volume percent of CNTs and considering magnetic field, material length scale parameter and viscoelastic medium, the frequency of the system increases and critically damped situation occurs at higher values of damper constant. In addition, the structure with FGX distribution type of CNTs has the highest stiffness. It is also observed that increasing temperature, structural damping and central angle of curved microbeam decreases the frequency of the system.

Key Words
vibration analysis; FG-CNTs-reinforced composite; curved microbeam; Timoshenko beam; strain gradient theory; magnetic field; viscoelastic medium

(1) Farshid Allahkarami, Mansour Nikkhah-Bahrami:
Department of Mechanical and Aerospace Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;
(2) Maryam Ghassabzadeh Saryazdi:
Vehicle Technology Research Institute, Amirkabir University of Technology, Tehran, Iran.

The novelty of this work is the use of a new displacement field that includes undetermined integral terms for analyzing thermal buckling response of functionally graded (FG) sandwich plates. The proposed kinematic uses only four variables, which is even less than the first shear deformation theory (FSDT) and the conventional higher shear deformation theories (HSDTs). The theory considers a trigonometric variation of transverse shear stress and verifies the traction free boundary conditions without employing the shear correction factors. Material properties of the sandwich plate faces are considered to be graded in the thickness direction according to a simple power-law variation 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 assumed as uniform, linear and non-linear temperature rises within the thickness direction. An energy based variational principle is employed to derive the governing equations as an eigenvalue problem. The validation of the present work is checked by comparing the obtained results the available ones in the literature. The influences of aspect and thickness ratios, material index, loading type, and sandwich plate type on the critical buckling are all discussed.

Key Words
thermal buckling; sandwich plate; functionally graded materials; plate theory

(1) Abderrahmane Menasria, Abdelhakim Bouhadra, Abdelouahed Tounsi, Abdelmoumen Anis Bousahla:
Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(2) Abderrahmane Menasria, Abdelhakim Bouhadra:
Université de Abbés Laghrour Khenchela, Faculté de Sciences & Technologie, Département de Génie Civil, Algeria;
(3) Abdelouahed Tounsi:
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de Génie Civil, Algeria;
(4) Abdelouahed Tounsi, Abdelmoumen Anis Bousahla:
Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algeria;
(5) Abdelmoumen Anis Bousahla:
Centre Universitaire de Relizane, Algerié;
(6) S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia.

In this work, the model of magneto-thermoelasticity based on memory-dependent derivative (MDD) is applied to a one-dimensional thermal shock problem for a functionally graded half-space whose surface is assumed to be traction free and subjected to an arbitrary thermal loading. The Lamé's modulii are taken as functions of the vertical distance from the surface of thermoelastic perfect conducting medium in the presence of a uniform magnetic field. Laplace transform and the perturbation techniques are used to derive the solution in the Laplace transform domain. A numerical method is employed for the inversion of the Laplace transforms. The effects of the time-delay on the temperature, stress and displacement distribution for different linear forms of Kernel functions are discussed. Numerical results are represented graphically and discussed.

Key Words
magneto-thermoelasticity; FGMs; variable Lamé's modulii; memory-dependent derivatives; perturbation method; numerical results

(1) Magdy A. Ezzat:
Department of Mathematics, Faculty of Education, Alexandria University, Alexandria, Egypt;
(2) Alaa A. El-Bary:
Arab Academy for Science and Technology, P.O. Box 1029, Alexandria, Egypt.

In this work, transient thermo-piezo-elastic responses of an infinite functionally graded piezoelectric (FGPE) plate whose upper surface suffers time-dependent thermal shock are investigated in the context of different thermo-piezo-elastic theories. The thermal and mechanical properties of functionally graded piezoelectric plate under consideration are expressed as power functions of plate thickness variable. The solution of problem is obtained by solving the corresponding finite element governing equations in time domain directly. Transient thermo-piezo-elastic responses of the FGPE plate, including temperature, stress, displacement, electric intensity and electric potential are presented graphically and analyzed carefully to show multi-field coupling behaviors between them. In addition, the effects of functionally graded parameters on transient thermo-piezo-elastic responses are also investigated to provide a theoretical basis for the application of the FGPE materials.

Key Words
transient thermo-piezo-elastic responses; thermal shock; multi-field coupling behavior; functionally graded piezoelectric plate

(1) Qi-lin Xiong:
Department of Mechanics, Huazhong University of Science & Technology, 1037 Luoyu Road, Wuhan 430074, China;
(2) Qi-lin Xiong:
Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, 1037 Luoyu Road, Wuhan 430074, China;
(3) Xin Tian:
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.

In this paper, Coriolis effect on vibration behavior of a rotating rectangular plate made of functionally graded (FG) materials under thermal loading has been investigated. The material properties of the FG plate are supposed to get changed in parallel with the thickness of the plate and the thermal properties of the material are assumed to be thermo-elastic. In this research, the effect of hub size, rotating speed and setting angle are considered. Governing equation of motion and the associated boundary conditions are obtained by Hamilton's principle. Generalized differential quadrature method (GDQM) is used to solve the governing differential equation with respect to cantilever boundary condition. The results were successfully verified with the published literatures. These results can be useful for designing rotary systems such as turbine blades. In this work, Coriolis and thermal effects are considered for the first time and GDQM method has been used in solving the equations of motion of a rotating FGM plate.

Key Words
functionally graded plate; vibration; Coriolis effect; thermal environment; GDQM method

Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, 3414916818, Qazvin, Iran.

In this paper, the analysis of the behavior of surface cracks in finite-thickness plates repaired with a Boron/Epoxy composite patch is investigated using three-dimensional finite element methods. The stress intensity factor at the crack-front was used as the fracture criteria. Using the Ansys Parametric Design Language (APDL), the stress intensities at the internal and external positions of repaired surface crack were compared. The effects of the mechanical and geometrical properties of the adhesive layer and the composite patch on the variation of the stress intensity factor at the crack-front were examined.

Key Words
patch; stress intensity factor; surface cracks; bonded composite repairs

Mohamed Merzoug, Abdelkader Boulenouar and Mohamed Benguediab: Laboratory of Materials and Reactive Systems - LMSR. University of Sidi Bel Abbes. BP. 89, City Larbi Ben Mhidi. Sidi Bel Abbes, Algeria

The effect of column loss location on the structural response of steel moment resisting frames (MRF) is investigated in this study. A series of nonlinear static and dynamic analyses were performed to determine the resistance of a generic frame to an arbitrary column loss and detect the structural members that are susceptible to failure progression beyond that point. Both force-controlled and deformation-controlled actions based on UFC 4-023-03 and ASCE/SEI 41-06 were implemented to define the acceptance criteria for nine APM cases defined in this study. Results revealed that the structural resistance against an arbitrary column loss in the top story is at least 80% smaller than that of the bottom story. In addition, it was found that the dynamic increase factor (DIF) at the failure point is at most 1.13.

Key Words
progressive collapse; failure; vertical incremental dynamic analysis; failure overload factor; pushdown

(1) Farshad Hashemi Rezvani:
School of Civil Engineering, University of Queensland, Brisbane, Australia;
(2) Ann E. Jeffers:
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI, USA;
(3) Behrouz Asgarian:
Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran;
(4) Hamid Reza Ronagh:
Institute for Infrastructure Engineering, Western Sydney University, Australia.

This paper presents the structural identification of an arch dam model for the damaged, repaired and strengthened conditions under different water levels. For this aim, an arch dam-reservoir-foundation model has been constructed. Ambient vibration tests have been performed on the damaged, repaired and strengthened dam models for the empty reservoir (0 cm), 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and full reservoir (60 cm) water levels to illustrate the effects of water levels on the dynamics characteristics. Enhanced Frequency Domain Decomposition Method in the frequency domain has been used to extract the dynamic characteristics. The dynamic characteristics obtained from the damaged, repaired and strengthened dam models show that the natural frequencies and damping ratios are considerably affected from the varying water level. The maximum differences between the frequencies for the empty and full reservoir are obtained as 16%, 33%, and 25% for damaged, repaired and strengthened model respectively. Mode shapes obtained from the all models are not affected by the increasing water level. Also, after the repairing and strengthening implementations, the natural frequencies of the arch dam model increase significantly. After strengthening, between 46-92% and 43-62% recovery in the frequencies are calculated for empty and full reservoir respectively. Apparently, after strengthening implementation, the mode shapes obtained are more acceptable and distinctive compared to those for the damaged model.

Key Words
ambient vibration test; dynamic characteristics; enhanced frequency domain decomposition; prototype arch dam-reservoir-foundation model; repairing; reservoir water effect; strengthening

(1) A.C. Altunisik, S. Adanur:
Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey;
(2) M. Gunaydin:
Department of Civil Engineering, Gümüşhane University, Gümüşhane, Turkey;
(3) B. Sevim:
Department of Civil Engineering, Yıldız Technical University, Istanbul, Turkey.

The performance of an Industrialised Building System (IBS) consists of prefabricated reinforced concrete components, is greatly affected by the behaviour of the connection between beam and columns. The structural characteristics parameters of a beam-to-column connection like rotational stiffness, strength and ductility can be explained by load-rotation relationship of a full scale H-subframe under gravitational load. Furthermore, the connection

Key Words
Industrialised Building System (IBS); rotational behaviour; precast hybrid-steel concrete; experimental test; beam-to-column connection

(1) Mostafa Moghadasi:
Civil Engineering Department, Engineering Faculty, Bu-Ali Sina University, Hamedan, Iran;
(2) Abdul Kadir Marsono:
Civil Engineering Faculty, Universiti Teknologi Malaysia (UTM), Skudai, Johor, Malaysia;
(3) Seyed Esmaeil Mohammadyan-Yasouj:
Young Researchers and Elite Club, Najafabad Branch, Islamic Azad University, Najafabad, Iran

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