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CONTENTS
Volume 10, Number 5, October 2021
 


Abstract
The aim of the present study is to investigate a coupled arch dam-reservoir-massed foundation problem under two earthquake input mechanisms. The problem nonlinearity originates from opening/slipping of the vertical contraction joints of the dam body. The reservoir-structure interaction is taken into account assuming compressible reservoir. Also, the meshing approach (structured mesh vs. unstructured one) in the foundation medium is investigated. The Karoun-I double curvature arch dam is selected as a case study. Three components of the 1994 Northridge earthquake are selected as the free-field ground motion. A deconvolution analysis in 3D space is conducted to adjust the amplitude and frequency contents of the earthquake ground motion applied to the bottom of the massed foundation to determine the desired acceleration response at various points on the dam-foundation interface taking into account the coupling between the foundation and the structure. It is found that in the deconvolved earthquake input models, the maximum tensile and the compressive stresses increase by 19% and 12%, respectively in comparison with those of the free-field input models. In addition, modeling foundation using the unstructured mesh decreases the maximum compressive stresses within the dam body by about 20% in comparison with that obtained using the structured mesh model. In the same way, the maximum crest displacements in the horizontal direction decreases by about 30%.

Key Words
3D earthquake excitation; coupled dam-reservoir-massed foundation; deconvolution; unstructured meshing

Address
M. Varmazyari, S.R. Sabbagh-Yazdi and H. Mirzabozorg: Structural Engineering Department, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

Abstract
This paper presents a careful theoretical investigation into interfacial shear stresses in steel beam strengthened with prestressed carbon/glass hybrid laminated plate. A closed-form rigorous solution for interfacial shear stress in steel beams strengthened with bonded prestressed carbon/glass hybrid laminated plates and subjected to a uniformly distributed load, is developed using linear elastic theory and including the variation in fiber volume fraction of carbon/glass hybrid laminated. The results show that there exists a high concentration of shear stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the proportions and volume fraction of the fiber of carbon/glass hybrid laminated, the thickness of the laminate and the effect of prestressing where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This solution is intended for application to beams made of all kinds of materials bonded with a thin composite plate. This research is helpful for the understanding on mechanical behaviour of the interface and design of such structures.

Key Words
carbon/glass hybrid laminated; prestressed plate; shear stresses; steel beam; strengthening

Address
Hassaine Daouadji Tahar, Rabahi Abderezak and Benferhat Rabia: Civil Engineering Department, University of Tiaret, Algeria; Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Abstract
Connections play a significant role on the seismic performance of structures subjected to gravity and lateral loads. One of the most important strategies for plastic hinge transfer is the strengthening of connections. Composite and welded connections are commonly used in steel bridges. Each of these connections can affect the structural response to lateral loads such as cyclic loads. In this study, four steel bridge models with different types of connections, including composite and welded connections, are created in the finite element (FE) platform ABAQUS. After validation of a FE model using available experimental data, cyclic loading has been employed according to the load history proposed by Scientific Advisory Committee (SAC). The results indicate that using composite connections can increase shear capacity and improve ductility of the system. Also using composite connection can transfer stress concentrated from connection to other areas.

Key Words
composite connection; dissipated energy; hysteretic curve; steel bridges; weld connection

Address
Ali Naseri: Department of Structural Engineering, Babol Noshirvani University of Technology, Iran
Alireza Mirzagoltabar Roshan: Faculty of Civil Engineering, Babol Noshirvani University of Technology, Iran
Asghar Sabzevari: Department of Earthquake Engineering, University of Pardisan, Mazandaran, Iran

Abstract
This study aims to investigate the effect of cavity on electric energy harvesting from cantilever beam vibrations under electrostatic actuation. Electrostatic actuation is created by a layer of radioisotope materials that is placed on the opposite side of the beam emitting electrons. When the beam is charged, the electrostatic force is generated between the beam and the opposite plate and pulls the beam towards itself. After the beam strikes the radioisotope, it is electrically discharged and then released. The piezoelectric layer converts the released microbeam vibration into electricity. The equations of motion coupled with the electrical effects of the piezoelectric layer are extracted using Hamilton's principle and Gauss's law. The equations are discretized by Galerkin method. The exact mode shape of the cantilever beam with the piezoelectric layer is employed as the comparison function. By identifying the relations governing the system, the output voltage and consequently the amount of harvested electrical energy are obtained using various parameters such as thickness and position of the cavity and system electrical resistance. The results indicates that creating cavity has a significant effect on the energy harvesting.

Key Words
cavity; electrostatic; energy harvester; microcantilever; piezoelectric

Address
Kourosh Delalat, Mehdi Zamanian and Behnam Firouzi: Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, Mofatteh Avenue, P.O.
Box 15719-14911, Tehran, Iran

Abstract
Thermomechanical loading is considered to examine the non-local and phase-lags effects in a modified couple stress thermoelastic (MCT) half space. Governing equations are solved by using Laplace and Fourier transform techniques. Concentrated source in time and distributed sources with space variable are taken to demonstrate the application. Distributed sources are further classified as uniformly distributed source (UDS) and linearly distributed source (LDS) for mechanical, thermal and chemical potential sources. Numerical results are calculated for displacements, stresses, temperature distribution and chemical potential and are disucussed by displaying graphically. Some particular cases are deduced.

Key Words
dual-phase-lag; Laplace and Fourier transforms; LDS; modified couple stress thermoelasticity; non-local; UDS

Address
Rajneesh Kumar: Department of Mathematics, Kurukshetra University, Kurukshetra-136119 Haryana, India
Sachin Kaushal and Vikram Dahiya: Department of Mathematics, School of Chemical Engineering and Physical Sciences, Lovely Professional University-144411 Phagwara, India


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