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Estimating terminal velocity of rough cracks in the framework of discrete fractal fracture mechanics
, Article Engineering Fracture Mechanics ; Volume 77, Issue 10 , 2010 , Pages 1516-1526 ; 00137944 (ISSN) ; Khezrzadeh, H ; Sharif University of Technology
2010
Abstract
In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed
On the effect of large deflection on nonlinear behavior of an eccentric bracing system
, Article Structural Design of Tall and Special Buildings ; Volume 17, Issue 4 , 2008 , Pages 795-808 ; 15417794 (ISSN) ; Mofid, M ; Khezrzadeh, H ; Sharif University of Technology
2008
Abstract
In this article, a particular off-center bracing system is introduced. In this system, the tensile diagonal strut is not straight. When the load is applied, the original geometry changes and thus causes the system to harden. Based on this behavior, a step-by-step analytical method is developed. Using this method, a Geometrically Nonlinear Analysis Program (GNAP) is designed to analyze the elastic force-displacement relation. Extension of this program to dynamic analysis led to a Dynamic Nonlinear Analysis Program (DNAP). The object of this article is to show that such bracing systems will lead to less seismic force on such structures compared to classic concentric bracing systems. On the...
Experimental and numerical evaluation of piston metallic damper (PMD)
, Article Journal of Constructional Steel Research ; Volume 154 , 2019 , Pages 99-109 ; 0143974X (ISSN) ; Khezrzadeh, H ; Mofid, M ; Jafari, K ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this paper, a metallic yielding damper, called piston metallic damper (PMD) is introduced for the first time. The PMD is comprised of a set of parallel hollow circular plates that interconnect inner shaft of the PMD to its outer pipe. Experiments and numerical models are used to examine its applicability as a seismic energy dissipating device. In this novel damper seismic input energy will be dissipated through flexural yielding of circular steel plates when system experiences small to medium displacements. At large displacements, tensile behavior will dominate and causes significant increase in stiffness of the system. In experimental program, different specimens were tested and the...
Mechanical properties of pultruded GFRP profiles under seawater sea sand concrete environment coupled with UV radiation and moisture
, Article Construction and Building Materials ; Volume 258 , 2020 ; Zhao, X. L ; Jafari, A ; Ashrafi, H ; Bai, Y ; Singh Raman, R. K ; Khezrzadeh, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this research, the mechanical properties of various glass fibre reinforced polymer (GFRP) pultruded profiles exposed to seawater sea sand concrete (SWSSC) and its combination with UV radiation and water vapour condensation were studied. The effect of different conditions, duration of conditioning, and the profile cross-section configuration on the mechanical properties were investigated. Three-point bending, tension, and compression tests were carried out to obtain the mechanical properties, including flexural, tensile and compressive strengths and tensile elastic modulus. Furthermore, in order to scrutiny the mechanisms and extent of damage, scanning electron microscopy (SEM) was carried...
Durability of glass-fibre-reinforced polymer composites under seawater and sea-sand concrete coupled with harsh outdoor environments
, Article Advances in Structural Engineering ; 2020 ; Zhao, X. L ; Jafari, A ; Ashrafi, H ; Raman, R. K. S ; Bai, Y ; Khezrzadeh, H ; Sharif University of Technology
SAGE Publications Inc
2020
Abstract
This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were...
Durability of glass-fibre-reinforced polymer composites under seawater and sea-sand concrete coupled with harsh outdoor environments
, Article Advances in Structural Engineering ; Volume 24, Issue 6 , 2021 , Pages 1090-1109 ; 13694332 (ISSN) ; Zhao, X. L ; Jafari, A ; Ashrafi, H ; Raman, RK. S ; Bai, Y ; Khezrzadeh, H ; Sharif University of Technology
SAGE Publications Inc
2021
Abstract
This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were...