Loading...
Search for: moazezi-mehretehran--a
0.161 seconds

    3D buckling assessment of cylindrical steel silos of uniform thickness under seismic action

    , Article Thin-Walled Structures ; Volume 131 , 2018 , Pages 654-667 ; 02638231 (ISSN) Moazezi Mehretehran, A ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    This paper investigates the dynamic buckling behavior of steel silos subjected to horizontal base excitations. The elastic-plastic buckling resistance of three silos with different aspect ratios is estimated using Incremental Dynamic Analyses (IDA). Accordingly, the critical base shear, base moment and the peak ground acceleration (PGA) at the buckling instant are calculated. Moreover, the additional normal pressures induced from bulk solids on silo walls are evaluated and compared with those of Eurocode 8. The results obtained suggest that slender silos are more vulnerable to buckling failure, while squatter silos represent a considerably higher resistance under same seismic conditions. ©... 

    Investigation into the Behavior of Cylindrical Steel Silos Composed of Flat or Corrugated Sheets

    , Ph.D. Dissertation Sharif University of Technology Moazezi Mehretehran, Alireza (Author) ; Maleki, Shervin (Supervisor)
    Abstract
    Steel cylindrical silos are one of the most practical structures in handling and storage of bulk solids in many industries and agricultural sectors. Steel silos may be composed of flat or corrugated sheets. Due to small wall thickness, shell structures are vulnerable to buckling failure. Unsymmetrical loading conditions rising from frequent filling and discharge cycles during the lifetime of these storages are almost the main reason for local or global instability of silos. However, they may experience additional lateral loads such as, wind load and seismic load that essentially impose unsymmetrical pressure on shell walls and can lead to buckling, as well. Under wind pressure, steel... 

    Investigating the Behavior of Vertical Stiffeners' Bolted Connections to the Wall of Steel Corrugated Silos

    , M.Sc. Thesis Sharif University of Technology Seyedsharifi, Sama (Author) ; Moazezi Mehretehran, Alireza (Supervisor)
    Abstract
    In this study, the bolted connection of two steel corrugated plates, commonly found in silo walls, was investigated. Following the validation of FEM models, the test design described in AISI S905 for cold-formed steel bolted connections was referenced. The geometry of the corrugated plates was selected in accordance with ASTM A796. The effects of various parameters, including plate thickness, bolt diameter, steel type, bolt placement, wave geometry, and restrained curling, were analyzed with respect to the bearing capacity of the connections. Based on the analysis, the most significant parameters were identified, and 54 additional models were developed to further investigate the interaction... 

    Behavior of High-Strength Bolted Connections in Corrosive Environmental Conditions

    , M.Sc. Thesis Sharif University of Technology Mehditabar, Mohammad Reza (Author) ; Moazezi Mehretehran, Alireza (Supervisor)
    Abstract
    Steel connections are constantly exposed to strength degradation due to corrosion. The extent of this reduction varies based on preventive measures and environmental corrosion severity. To more accurately evaluate the performance of bolted steel structures in corrosive conditions, it is necessary to define the behavior of corroded bolted connections and incorporate it into structural analyses. A literature review in this area reveals that most previous studies have focused on the behavior of structural members, with very few addressing the impact of pitting corrosion on connections. Therefore, this research aims to examine the performance of bearing connections under pitting corrosion and to... 

    Investigation into Circular Steel Tubes with Pitting Corrosion under Axial Compression and Bending Moment

    , M.Sc. Thesis Sharif University of Technology Salehi, Nazanin Fatemeh (Author) ; Moazezi Mehretehran, Alireza (Supervisor)
    Abstract
    In this research the behavior of Circular Steel Tubes (CSTs) with corrosion under axial force and bending have been studied. There are several factors leading to corrosion in steel structures, especially marine structures that results in strength reduction of whole structure. Steel tubes are widely used in construction of on-shore and off-shore structures such as, oil rigs and platforms, oil and gas transmission lines. Current study focus on strength reduction of steel tubes with “pitting corrosion”. To this end numerical analyses using finite element software, Abaqus, have been performed. Therefore, utilizing verified models, the simultaneous effect of bending, axial load and corrosion on... 

    3D wind buckling analysis of long steel corrugated silos with vertical stiffeners

    , Article Engineering Failure Analysis ; Volume 90 , 2018 , Pages 156-167 ; 13506307 (ISSN) Maleki, S ; Moazezi Mehretehran, A ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Thin-walled cylindrical steel silos are susceptible to instability under wind pressure when they are empty or only partially filled. This paper investigates numerically the wind buckling behavior of a real steel corrugated silo with 8.02 m diameter and 17.62 m height, strengthened by open-section vertical stiffeners. Accordingly, comprehensive 3D finite element models were used and detailed linear and non-linear buckling analyses were conducted. The effects of sinusoidal corrugated sheet profile dimensions on this issue were specially explored. Wind load vertical and circumferential distributions were adopted from Eurocode. Two proposed circumferential pressure distributions for an isolated... 

    Seismic response and failure modes of steel silos with isotropic stepped walls: The effect of vertical component of ground motion and comparison of buckling resistances under seismic actions with those under wind or discharge loads

    , Article Engineering Failure Analysis ; Volume 120 , 2021 ; 13506307 (ISSN) Mehretehran, A. M ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Steel silos are one of the main structures for bulk solids handling and storage in many industries and agricultural sectors. A growing body of research suggests the importance of including the vertical component of earthquake ground motion in seismic analysis and design of certain structures. In the case of steel silos, this may induce additional meridional compression to exacerbate buckling failures in such thin shells. Accordingly, this paper investigates the buckling behavior of three cylindrical steel silos (i.e., a squat, an intermediate slender and a slender silo) with stepped walls subjected to horizontal only (H) and horizontal and vertical (HV) ground accelerations to address this... 

    Axial buckling of imperfect cylindrical steel silos with isotropic walls under stored solids loads: FE analyses versus Eurocode provisions

    , Article Engineering Failure Analysis ; Volume 137 , 2022 ; 13506307 (ISSN) Mehretehran, A. M ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Stored solids loads on silo vertical walls are composed of two orthogonal components: the horizontal component that internally pressurizes the silo and the vertical wall frictional component that causes axial compression. For an imperfect cylinder, the elastic axial buckling resistance may be considerably raised by a uniform internal pressure as it alleviates the detrimental effect of the geometrical imperfections. However, at high internal pressures, the combination of axial compression and circumferential tension may result into a plastic instability that is commonly termed elephant's foot buckling. Both stabilizing and destabilizing effects of internal pressure are taken into account by... 

    Buckling Strength of Cylindrical Shells with the Cutouts

    , M.Sc. Thesis Sharif University of Technology Rezaee, Kamyab (Author) ; moazezi mehr Tehran, Alireza (Supervisor)
    Abstract
    Cylindrical steel shells are common industrial structures. Due to their thin thickness, these structures are very susceptible to buckling under applied loads. For access and repair purposes, cutouts of various shapes and dimensions are used in these structures. The presence of such cutouts increases the sensitivity of these structures to buckling; therefore, it is necessary to use stiffeners with different dimensions and shapes around the opening to restore the lost capacity. Cylindrical shells are designed in different lengths for use in different structures. The most common shapes of these structures are silos, tanks, and turbines. Due to the effect of the slenderness of these structures... 

    Study of Corrugated Steel Plate Honeycomb Damper Performance

    , M.Sc. Thesis Sharif University of Technology Jafari, Mehrdad (Author) ; Moazezi Mehre Tehran, Alireza (Supervisor)
    Abstract
    In this study a new metallic damper, namely Corrugated steel plate Honeycomb Damper (CHD) is presented. The CHD proposed ease of manufacturing and implementation in various structures with a stable energy dissipation characteristic when subjected to lateral loading. The basic configuration of the CHD consists of two steel plates that are bent to form trapezoidal corrugations. The plates are then welded together along the bent lines to build the honeycomb geometry. In order to investigate the behavior of the CHD, first a closed-form expression for the elastic stiffness and yield strength was obtained by the matrix analysis method. Then, to study the non-linear behavior of the CHD, three... 

    Investigation of Shear Strength of Fillet Weld under In-Plane Eccentricity

    , M.Sc. Thesis Sharif University of Technology Rezaei, Alireza (Author) ; Maleki, Shervin (Supervisor) ; Moazezi Mehre Tehran, Alireza (Supervisor)
    Abstract
    The principal objective of this investigation is to furnish a straightforward and effective technique for computing the load-bearing capacity of fillet welds when subjected to in-plane eccentric loads. Some approaches have been put forth to ascertain the load-carrying capability of fillet welds under such conditions over time. The existing design methods, such as the conventional elastic method, are very conservative and do not match the test results well due to neglecting the weld group's ductility and strain compatibility. On the other hand, the instantaneous center of rotation method (IC) considers the above parameters but requires complex calculations. Therefore, in the present study, a... 

    Intelligent semi-active vibration control of eleven degrees of freedom suspension system using magnetorheological dampers

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , 2012 , Pages 323-334 ; 1738494X (ISSN) Zareh, S. H ; Sarrafan, A ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
    2012
    Abstract
    A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network... 

    Performance and exhaust emission characteristics of a spark ignition engine operated with gasoline and CNG blend

    , Article Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division ; 2012 , Pages 179-187 ; 15296598 (ISSN) ; 9780791844663 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
    2012
    Abstract
    Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the... 

    A comparative study of the performance of a SI engine fuelled by natural gas as alternative fuel by thermodynamic simulation

    , Article 2009 ASME Internal Combustion Engine Division Fall Technical Conference, ICEF 2009, Lucerne, 27 September 2009 through 30 September 2009 ; 2009 , Pages 49-57 ; 9780791843635 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2009
    Abstract
    With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost... 

    Analytical and experimental analyses of nonlinear vibrations in a rotary inverted pendulum

    , Article Nonlinear Dynamics ; Volume 107, Issue 3 , 2022 , Pages 1887-1902 ; 0924090X (ISSN) Dolatabad, M.R ; Pasharavesh, A ; Khayyat, A. A. A ; Sharif University of Technology
    Springer Science and Business Media B.V  2022
    Abstract
    Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing... 

    A suction-controlled ring device to measure the coefficient of lateral soil pressure in unsaturated soils

    , Article Geotechnical Testing Journal ; Volume 44, Issue 1 , 2020 Pirjalili, A ; Garakani, A. A ; Golshani, A ; Mirzaii, A ; Sharif University of Technology
    ASTM International  2020
    Abstract
    A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring... 

    Gum tragacanth gels as a new supporting matrix for immobilization of whole-cell

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 24, Issue 4 , 2005 , Pages 1-7 ; 10219986 (ISSN) Otady, M ; Vaziri, A ; Seifkordi, A. A ; Kheirolomoom, A ; Sharif University of Technology
    2005
    Abstract
    We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems. The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity. The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction. This signifies the potential of GT as a biocompatible matrix for... 

    True Class-E Design For Inductive Coupling Wireless Power Transfer Applications

    , Article 30th International Conference on Electrical Engineering, ICEE 2022, 17 May 2022 through 19 May 2022 ; 2022 , Pages 864-868 ; 9781665480871 (ISBN) Haeri, A. A. R ; Safarian, A ; Fotowat Ahmady, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    The Class-E power amplifier has been widely studied and formulated in the literature. Although the majority of reported inductive coupling wireless power transfer (WPT) systems use a class-E power amplifier for driving the primary coil, still there is a lack of a comprehensive study on class-E circuit dedicated to WPT, providing a set of closed form design equations for proper class-E operation. This paper presents the required design equations needed to design a 'true' class-E circuit for WPT applications. Equations for the series-tuned secondary coil WPT system are presented, as well as two different design procedures for the parallel-tuned secondary coil. The derived equations have been... 

    Crashworthiness determination of side doors and B pillar of a vehicle subjected to pole side impact

    , Article Applied Mechanics and Materials ; Vol. 663, issue , 2014 , p. 552-556 Lilehkoohi, A. H ; Faieza, A. A ; Sahari, B. B ; Nuraini, A. A ; Halali, M ; Sharif University of Technology
    2014
    Abstract
    Pole Side Impact Tes is one out of three crash tests described by Euro NCAP standard for star rating of a vehicle and is required for assessing the Adult Occupant Protection. In this paper the goal is to determine the crashworthiness of side doors and B pillar in a Pole Side Impact Test based on Euro New Car Assessment Program (Euro-NCAP) using computer and simulation method. In this matter, a vehicle model has been prepared and meshed using Hypermesh and CATIA. The velocity of 29 km/h has been assigned to the vehicle which was on top of a cart while the pole has been assigned as a rigid static object based on Euro NCAP requirements specifically. Results show that different amounts of energy... 

    Investigation of Thickness Influences On Energy Absorption For Side Doors And B Pillar In Euro NCAP Pole Side Impact Test

    , Article Applied Mechanics and Materials ; Vol. 663, issue , Oct , 2014 , p. 585-589 Lilehkoohi, A. H ; Faieza, A. A ; Sahari, B. B ; Nuraini, A. A ; Halali, M ; Sharif University of Technology
    2014
    Abstract
    To assess a car under the Euro New Car Assessment Program (Euro-NCAP), Adult Occupant Protection is one out of three parameters which need to be calculated with a weight factor of 50% while the other parameters, Child Occupant Protection and Pedestrian Occupant Protection, have a weight factor of 20%. The Pole Side Impact Test, beside two other tests, Side and Front Impact, is also required to calculate the Adult Occupant Protection. It shows how important the Pole Side Impact Test is and what an effective role it has in the car rating assessment. In this paper, the objective is to evaluate the effect of thickness on the energy absorbed by the side doors and the B pillar and its...