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CONTENTS
Volume 67, Number 3, August10 2018
 

Abstract
This paper deals with the static bending of various types of FGM sandwich plates resting on two-parameter elastic foundations in hygrothermal environment. The elastic foundation is modeled as Pasternak\'s type, which can be either isotropic or orthotropic and as a special case, it converges to Winkler\'s foundation if the shear layer is neglected. The present FGM sandwich plate is assumed to be made of a fully ceramic core layer sandwiched by metal/ceramic FGM coats. The governing equations are derived from principle of virtual displacements based on a shear and normal deformations plate theory. The present theory takes into account both shear and normal strains effects, thus it predicts results more accurate than the shear deformation plate theories. The results obtained by the shear and normal deformation theory are compared with those available in the literature and also with those obtained by other shear deformation theories. It is concluded that the present results are slightly deviated from other results because the normal deformation effect is taken into account. Numerical results are presented to show the effects of the different parameters, such as side-to-thickness ratio, foundation parameters, aspect ratio, temperature, moisture, power law index and core thickness on the stresses and displacements of the FG sandwich plates.

Key Words
sandwich plates; shear and normal deformation theory; hygrothermal bending; Pasternak foundation

Address
Mohammad Alakel Abazid: Department of Mathematics and Statistics, Faculty of Science, King Faisal University, P.O. Box 400, Hofuf, 31982, Saudi Arabia
Muneerah S. Alotebi: Department of Mathematics, Faculty of Arts and Science at Nairiyah, Hafr Al Batin University, P.O. Box 1803, Hafr Al Batin 31991, Saudi Arabia
Mohammed Sobhy: Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh 33516, Egypt

Abstract
This study aims at evaluating the performance of repairing technique with CFRPs in recovering cyclic performance of damaged columns in flexure in terms of structural response parameters such as strength, dissipated energy, stiffness degradation. A 2/3 scaled substandard reinforced concrete frame was constructed to represent the substandard RC buildings especially in developing countries. These substandard buildings have several structural deficiencies such as strong beam-weak column phenomenon, improper reinforcement detailing and poor material properties. Flexural plastic hinges occurred at the columns ends after testing the substandard specimen under both constant axial load and reversed cyclic lateral loading. Afterwards, the damaged columns were externally wrapped with CFRP sheets both in transverse and longitudinal directions and then retested under the same loading protocol. In addition, ambient vibration measurements were taken from the undamaged, damaged and the repaired specimens at each structural repair steps to identify the effectiveness of each repairing step by monitoring the change in the natural frequencies of the tested specimen. The ambient vibration test results showed that the applied repairing technique with external CFRP wrapping was proved to recover stiffness of the pre-damaged specimen. Moreover, the lateral load capacity of the pre-damaged substandard RC frame was restored with externally bonded CFRP sheets.

Key Words
reinforced concrete; CFRP; seismic repairing; ambient vibration; stiffness; flexural damage

Address
Burak Duran: Department of Civil Engineering, Dokuz Eylul University, Tinaztepe Campus, Izmir, Turkey
Onur Tunaboyu and Ozgur Avsar: Department of Civil Engineering, Anadolu University, 2 Eylul Campus, Eskisehir, Turkey
Onur Kaplan: Earth and Space Sciences Institute, Anadolu University, 2 Eylul Campus, Eskisehir, Turkey

Abstract
In this paper, a Cloud Model based Fruit Fly Optimization Algorithm (CMFOA) is presented for structural damage identification, which is a global optimization algorithm inspired by the foraging behavior of fruit fly swarm. It is assumed that damage only leads to the decrease in elementary stiffness. The differences on time-domain structural acceleration data are used to construct the objective function, which transforms the damaged identification problem of a structure into an optimization problem. The effectiveness, efficiency and accuracy of the CMFOA are demonstrated by two different numerical simulation structures, including a simply supported beam and a cantilevered plate. Numerical results show that the CMFOA has a better capacity for structural damage identification than the basic Fruit Fly Optimization Algorithm (FOA) and the CMFOA is not sensitive to measurement noise.

Key Words
damage identification; swarm intelligence; cloud model; fruit fly optimization algorithm; time domain data

Address
Tongyi Zheng, Jike Liu and Zhongrong Lu: Department of Applied Mechanics, Sun Yat-Sen University, Guangzhou, P.R. China
Weili Luo: School of Civil Engineering, Guangzhou University, Guangzhou, P.R. China

Abstract
The prestress force effect on the fundamental frequency and deflection shape of Prestressed Concrete I (PCI) beams was studied in this paper. Currently, due to the conflicts among existing theories, the analytical solution for properly considering the structural behavior of these prestressed members is not clear. A series of experiments were conducted on a large-scale PCI beam of high strength concrete with an eccentric straight unbonded tendon. Specifically, the simply supported PCI beam was subjected to free vibration and three-point bending tests with different prestress forces. Subsequently, the experimental data were compared with analytical results based on the Euler-Bernoulli beam theory. It was proved that the fundamental frequency of PCI beams is unaffected by the increasing applied prestress force, if the variation of the initial elastic modulus of concrete with time is considered. Vice versa, the relationship between the deflection shape and prestress force is well described by the magnification factor formula of the compression-softening theory assuming the secant elastic modulus.

Key Words
compression-softening theory; deflection shape; fundamental frequency; PCI beam; prestress force

Address
Marco Bonopera:
1) Bridge Engineering Division, National Center for Research on Earthquake Engineering, Taipei, Taiwan
2) Department of Engineering, University of Ferrara, Ferrara, Italy
Kuo-Chun Chang: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
Chun-Chung Chen: Bridge Engineering Division, National Center for Research on Earthquake Engineering, Taipei, Taiwan
Yu-Chi Sung:
1) Bridge Engineering Division, National Center for Research on Earthquake Engineering, Taipei, Taiwan
2) Department of Civil Engineering, National Taipei University of Technology, Taipei, Taiwan
Nerio Tullini: Department of Engineering, University of Ferrara, Ferrara, Italy

Abstract
A numerical study of soil-foundation system under monotonic and cyclic pushover loading is conducted, taking into account both material and geometric nonlinearities. A complete and refined 3D finite element (FE) model, using contact condition and allowing separation between soil and foundation, is implemented and used in order to evaluate the nonlinear relationship between applied vertical forces and induced settlements. Based on the obtained curve, a simplified model is proposed, in which the soil inelasticity is satisfactorily represented by two vertical springs with trilinear behavior law, and the foundation uplifting is insured by gap elements. Results from modeling soil-foundation system supporting a bridge pier have shown that the simplified model is able to capture irreversible settlements induced by cyclic rocking, due to soil inelasticity and vertical loading, as well as large rotations due to foundation uplifting.

Key Words
soil-foundation interaction; foundation uplifting; soil inelasticity; pushover analysis

Address
Ouassila Kada:
1) Civil Engineering Department, Faculty of Technology, University of Bejaia, Targua Ouzemour, 06000, Algeria
2) Normandie University, UNIHAVRE, CNRS, LOMC, 53 rue Prony, CS 80540, 76058 Le Havre Cedex, France
Ahmed Benamar: Normandie University, UNIHAVRE, CNRS, LOMC, 53 rue Prony, CS 80540, 76058 Le Havre Cedex, France
Abdelkader Tahakourt: Laboratoire de Génie de Construction et Architecture (LGCA), Faculty of Technology, University of Bejaia, Targua Ouzemour, 06000, Algeria

Abstract
The analytical solution of two functionally graded layers with Volterra type screw dislocation is investigated under anti-plane shear impact loading. The energy dissipation of FGM layers is modeled by viscous damping and the properties of the materials are assumed to change exponentially along the thickness of the layers. In this study, the rate of gradual change of shear moduli, mass density and damping constant are assumed to be same. At first, the stress fields in the interface of the FGM layers are derived by using a single dislocation. Then, by determining a distributed dislocation density on the crack surface and by using the Fourier and Laplace integral transforms, the problem are reduce to a system of singular integral equations with simple Cauchy kernel. The dynamic stress intensity factors are determined by numerical Laplace inversion and the distributed dislocation technique. Finally, various examples are provided to investigate the effects of the geometrical parameters, material properties, viscous damping and cracks configuration on the dynamic fracture behavior of the interacting cracks.

Key Words
two FGM layers; viscous damping; transient anti-plane loading; several interface cracks

Address
Mehrdad Fallahnejad, Rasul Bagheri and Masoud Noroozi: Department of Mechanical Engineering, Mechatronics Faculty, Karaj Branch, Islamic Azad University, Alborz, Iran

Abstract
This paper presents the results of a study that investigated the influence of using recycled coarse aggregate (RCA) and recycled asphalt pavement (RAP) on the properties of pervious concrete (PC). The natural aggregate (NA) was replaced by RCA and RAP in the PC with replacement levels of 0%, 20%, 40%, 60% and 80% by the total weight of NA, respectively. In addition to incorporating RAP and RCA in the same mixes with replacement levels of: (1) 20% RAP and 80% RCA; (2) 60% RAP and 40% RCA; and (3) 80% RAP and 20% RCA. Water permeability, thermal conductivity, density, porosity, void content, and compressive, splitting tensile and flexural strengths were studied in this paper. The results showed that using RCA, RAP, and (RAP-RCA) enhanced the properties of PC in general and improved the mechanical properties significantly in particular. The optimum mix was reported to be the 60% RAP and 40% RCA. Accordingly, the RAP has the potential to be used in PC in order to reduce the negative impact of RAP on the human health and environment.

Key Words
recycled coarse aggregate; recycled asphalt pavement; pervious concrete; mechanical properties; thermal conductivity

Address
Nasim K. Shatarat: Civil Engineering Department, The University of Jordan, 11942, Amman, Jordan
Hasan N. Katkhuda and Khaled H. Hyari: Civil Engineering Department, The Hashemite University, P. O. Box 330127, 13115, Zarqa, Jordan
Ibrahim Asi: Arab Center for Engineering Studies, Amman, Jordan

Abstract
In this work, a new trigonometry theory of shear deformation is developed for the static analysis of thick isotropic beams. The number of variables used in this theory is identical to that required in the theory of Euler-Bernoulli, sine function is used in the displacement field in terms of the coordinates of the thickness to represent the effects of shear deformation. The advantage of this theory is that shear stresses can be obtained directly from the relationships constitute, while respecting the boundary conditions at the free surface level of the beam. Therefore, this theory avoids the use of shear correction coefficients. The differential equilibrium equations are obtained using the principle of virtual works. A thick isotropic beam is considered, whose numerical study to show the effectiveness of this theory.

Key Words
thick beam; high order theory; virtual working principle; bending

Address
Salima Abdelbari:
1) Departement de Genie Civil, Institut des Sciences et de la Technologie, Centre Universitaire de Ain Temouchent, Algeria
2) Civil Engineering Department, Faculty of Technology, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria
Lemya Hanifi Hachemi Amar:
1) Departement de Genie Civil et Hydraulique, Faculte de Technologie, Universite Dr Tahar Moulay, BP 138 Cite En-Nasr 20000 Saida, Algerie
2) Laboratoire des Ressources Hydriques et Environnement, Universite Dr Tahar Moulay, BP 138 Cite En-Nasr 20000 Saida, Algerie
Abdelhakim Kaci:
1) Civil Engineering Department, Faculty of Technology, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria
2) Departement de Genie Civil et Hydraulique, Faculte de Technologie, Universite Dr Tahar Moulay, BP 138 Cite En-Nasr 20000 Saida, Algerie
Abdelouahed Tounsi:
1) Civil Engineering Department, Faculty of Technology, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria
2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran,
Eastern Province, Saudi Arabia

Abstract
In this paper, a multi-objective multiparameter optimization procedure is developed by combining rigorously developed metamodels with an evolutionary search algorithm—Genetic Algorithm (GA). Response surface methodology (RSM) is used for developing the metamodels to replace the tedious finite element analyses. A nine-node isoparametric plate bending element is used for conducting the finite element simulations. Highly accurate numerical data from an author compiled FORTRAN finite element program is first used by the RSM to develop second-order mathematical relations. Four material parameters- E_1/E_2 , G_12/E_2 , G_23/E_2 and v_12 are considered as the independent variables while simultaneously maximizing fundamental frequency, lambda_1 and frequency separation between the 1st two natural modes, lambda_21. The optimal material combination for maximizing lambda_1 and lambda_21 is predicted by using a multi-objective GA. A general sensitivity analysis is conducted to understand the effect of each parameter on the desired response parameters.

Key Words
FE-surrogate; finite element; multi-objective; optimization; robust model

Address
Kanak Kalita, Pratik Nasre and Salil Haldar: Department of Aerospace Engineering and Applied Mechanics, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711 103, India
Partha Dey: Department of Mechanical Engineering, Academy of Technology, Adisaptagram, Hooghly 712 121, India

Abstract
Vibration of concrete beams reinforced by agglomerated silicon dioxide (SiO2) nanoparticles is studied based on numerical methods. The structure is simulated by Euler-Bernoulli beam model and the Mori-Tanaka model is used for obtaining the effective material properties of the structure. The concrete beam is located in soil medium which is modeled by spring elements. The motion equations are derived based on energy method and Hamilton\'s principle. Based on exact solution, the frequency of the structure is calculated. The effects of different parameters such as volume percent of SiO2 nanoparticles and agglomeration, soil medium and geometrical parameters of beam are shown on the frequency of system. The results show that with increasing the volume percent of SiO2 nanoparticles, the frequency increases.

Key Words
vibration; SiO2 nanoparticles; soil medium; concrete beam; exact solution

Address
Ali Heidari, Reza Keikha, Mohammad Salkhordeh Haghighi and Hamidreza Hosseinabadi: Department of Civil Engineering, Faculty of Engineering, University of Zabol, P.B. 9861335-856, Zabol, Iran


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