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Effects of viscoelastic supports on the behavior of bridges under moving vehicles
, Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1751-1769 ; 10263098 (ISSN) ; Vafai, H ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
One of the most important problems facing structural engineers is the analysis of dynamic behavior of bridges subjected to moving vehicles. In addition, viscoelastic supports under bridges change their dynamic behavior under passing traffic loads. This paper presents how to model a bridge with viscoelastic supports and how the maximum dynamic stress of bridges changes during the passing of moving vehicles. Furthermore, this paper presents an algorithm to solve the governing equation of the bridge with viscoelastic supports as well as the equation of motion of a real European truck with different speeds, simultaneously. Using viscoelastic supports with appropriate characteristics can make a...
Congestion effect on maximum dynamic stresses of bridges
, Article Structural Engineering and Mechanics ; Volume 55, Issue 1 , 2015 , Pages 111-135 ; 12254568 (ISSN) ; Vafaia, H ; Sharif University of Technology
Techno Press
2015
Abstract
Bridge behavior under passing traffic loads has been studied for the past 50 years. This paper presents how to model congestion on bridges and how the maximum dynamic stress of bridges change during the passing of moving vehicles. Most current research is based on mid-span dynamic effects due to traffic load and most bridge codes define a factor called the dynamic load allowance (DLA), which is applied to the maximum static moment under static loading. This paper presents an algorithm to solve the governing equation of the bridge as well as the equations of motions of two real European trucks with different speeds, simultaneously. It will be shown, considering congestion in eight case...
Scattering of SH-waves by an elliptic cavity/crack beneath the interface between functionally graded and homogeneous half-spaces via multipole expansion method
, Article Journal of Sound and Vibration ; Volume 435 , 2018 , Pages 372-389 ; 0022460X (ISSN) ; Shodja, H. M ; Sharif University of Technology
Academic Press
2018
Abstract
In this study, based on multipole expansion method an analytical treatment is presented for the anti-plane scattering of SH-waves by an arbitrarily oriented elliptic cavity/crack which is embedded near the interface between exponentially graded and homogeneous half-spaces. The cavity is embedded within the inhomogeneous half-space. The boundary value problem of interest is solved by constructing an appropriate set of multipole functions which satisfy (i) the governing equation in each half-space, (ii) the continuity conditions across the interface between the two half-spaces, and (iii) the far-field radiation and regularity conditions. The analytical expressions for the scattered...
Investigation of Dynamic Behavior of Beams with Different Supports under Moving Vehicles
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor) ; Esmaeil Pourestekanchi, Homayun (Co-Advisor)
Abstract
With the transportation progress and appearance of transit industry, necessity of modern vehicles redounded to appearance of heavier trucks with higher speeds, moving on the roads. In addition, with the progress in mechanical engineering and automobile industry, appearance of such trucks is growing increasingly. So, bridges as one of the structures that civil engineers design and construct, nowadays are subjected to higher moving dynamic loads in comparison with the past. As a result, lots of investigation and researches in the universities and institutions all over the world are being conducting on the effects of the vehicle speeds on the dynamic stresses of the bridges. Bridge codes...
Vibration Modeling of a Variable Section Beam under Moving Mass with Neural Networks Techniques
, M.Sc. Thesis Sharif University of Technology ; Ghaemi Osgouie, Kambiz (Supervisor) ; Khayyat, Amir Ali Akbar (Supervisor)
Abstract
The investigation of the behavior of structures subjected to various kinds of loadings is of considerable importance. In this research, an attempt was made to analyze behavior of beams that a load is moving on them.Most of the existing relevant works in this field are dealt with examination of elastic beams with constant section, while in most cases beams with variable sections are used in order to have the optimum structure and appropriate stress distribution and to maximize strength to weight or cost ratio. While construct analysis is very advantageous, it is very difficult due to the complexities arising from the variable sections. But this design is so advantageous that it dominates...
Atomistic simulations of mechanical properties and fracture of graphene: A review
, Article Computational Materials Science ; Volume 210 , 2022 ; 09270256 (ISSN) ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Material properties and fracture characteristics are among the most prominent parameters that should be considered for a wide range of graphene applications. This article reviews recent advances in theoretical studies on the mechanical properties and fracture behaviors of graphene, focusing on the effect of various simulation models. Most studies investigated single-layer graphene sheets (SLGSs) under uniaxial tensile tests using different common interatomic potentials, particularly AIREBO. Although researchers have examined a similar problem, specifically for pristine graphene, the differences in the reported values are considerable. These discrepancies are most evident in fracture...
Surface/Interface Effect on the Scattering of Love Waves by a Surface-Breaking Crack Within an Ultra-Thin Layer Bonded to an Elastic Half-Space
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossein (Supervisor)
Abstract
In this study, an analytical solution is presented for anti-plane scattering of Love waves by a surface-breaking crack normal to the free surface of an ultra-thin layer bonded to a semi-infinte medium within the surface/interface elasticity theory. The Fourier transform techniques are used to formulate the corresponding mixed-boundary value problem as a singular integral equation of the Cauchy type which is solved numerically. Mode III dynamic stress intensity factor at the crack tip, crack face and crack mouth opening displacements, the reflection coefficient at large distances from the crack face, and the stress field on the interface are computed and plotted for different valued of...
Scattering of SH-Waves by a Cylindrical Multi Inhomogeneity Embedded in a Piezo-Electromagnetic Medium Using an Analytical Innovative Micromechanical Approach
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
This work examines the problem of the fully coupled magneto-electro-elastic (MEE) scattering of SH-waves incident upon a heterogeneous MEE scatterer which is embedded in an unbounded medium. The scatterer consists of a circular core and a circular encapsulator with eccentricity. All three regions: the core, encapsulator, and the surrounding matrix have distinct MEE properties and fully coupled constitutive relations. The generated coupled MEE fields coexist simultaneously in all these regions without resort to any simplifying assumptions. The precise description of the multifunctionality involves the solution of three fully coupled partial differential equations in three different regions....
Effect of boundary conditions on dynamic behaviour of bridges
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 169, Issue 2 , 2016 , Pages 121-140 ; 09650911 (ISSN) ; Vafai, H ; Sharif University of Technology
Thomas Telford Services Ltd
Abstract
A moving vehicle, owing to its vibration and mass inertia, has significant effects on the dynamic response of structures. Most bridge codes define a factor called the dynamic load allowance, which is applied to the maximum static moment under static loading due to traffic load. This paper presents how to model an actual truck on bridges and how the maximum dynamic stresses of bridges change during the passage of moving vehicles. Furthermore, an algorithm to solve the governing equation of the bridge simultaneous with the equations of motion of an actual European truck is presented. Subsequently, 32 dynamic analyses of different bridges with different spans, road profiles and boundary...
Scattering of plane elastic waves by a multi-coated nanofiber with deformable interfaces
, Article International Journal of Solids and Structures ; Volume 141-142 , 2018 , Pages 195-218 ; 00207683 (ISSN) ; Taheri Jam, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The scattering of in-plane P- and SV-waves by a multi-coated circular nanofiber with deformable interfaces is of interest. To this end, in the present work, after introducing two kinds of interface momenta defined as the derivative of the interface excess kinetic energy with respect to the average and relative velocities at the interface, we extend the elastostatic theory of Gurtin et al. (1998) on deformable interfaces to the elastodynamic theory and derive the interface equations of motion using Hamilton principle. The effects of the generalized interface properties including the interface inertial parameters and interface stiffness towards stretch and slip on the dynamic stress...
An investigation on the validity of Cauchy-Born hypothesis using Sutton-Chen many-body potential
, Article Computational Materials Science ; Volume 44, Issue 3 , January , 2009 , Pages 999-1006 ; 09270256 (ISSN) ; Abdolhosseini Qomi, M. J ; Kazemi, M. T ; Aghaei, A ; Sharif University of Technology
2009
Abstract
The Cauchy-Born hypothesis has been used to concurrently bridge atomistic information to continuum model. It has been a prevalent assumption in computational nano-mechanics during the past decade. This kinematic assumption relates the deformation of the continuum to the deformation of its underlying crystalline structure. The main objective of this paper is to investigate the validity of this hypothesis by means of direct atomistic simulations and the continuum mechanic calculations. In fact, we intend to determine under which strain or stress state the crystalline structure undergoes inhomogeneous deformation due to a small perturbation of the homogeneously deformed system. Two failure...