Loading...
Search for:
mehretehran--a--m
0.195 seconds
Total 26730 records
3D wind buckling analysis of long steel corrugated silos with vertical stiffeners
, Article Engineering Failure Analysis ; Volume 90 , 2018 , Pages 156-167 ; 13506307 (ISSN) ; 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) ; 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) ; 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...
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) ; 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 ; 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 ; 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 ; 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 ; 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...
Theoretical study of high repetition rate short pulse generation with fiber optical parametric amplification [electronic resource]
, Article Journal of Lightwave Technology ; May 2012, Volume 30, Issue 9, PP. 1263-1268 ; Ariaei, A. M ; Jadidi, M. M ; Salehi, J. A ; Sharif Unversity of Technology
Abstract
In this paper, we study theoretically the generation of high repetition rate short pulses using fiber optical parametric amplification. We show that the pulse shape and duration depend on the signal location relatively to the pump frequency. We demonstrate that in order to get the shortest pulse width, the signal must be located at one of the extremities of the gain spectrum associated with the pump peak power. We derive the analytical expression of the pulse shape in this case and compare it to the exponential gain regime case. Using numerical simulations, we also analyze the impact of walk-off and pump phase modulation that is required to suppress Stimulated Brillouin Scattering and derive...
A novel omega shaped microwave absorber with wideband negative refractive index for C-band applications
, Article Optik ; Volume 242 , 2021 ; 00304026 (ISSN) ; Baqir, M. A ; Iftikhar, A ; Ali, M. M ; Rahim, A. A ; Niaz Akhtar, M ; Mughal, M. J ; Naqvi, S. A ; Sharif University of Technology
Elsevier GmbH
2021
Abstract
This paper reports a polarization controllable and angle-insensitive perfect metamaterial absorber (PMA). The proposed PMA consists of periodically arranged asymmetric omega-shaped resonators made of metallic copper. The absorptivity was analyzed considering the microwave C-band from 4 GHz to 8 GHz. The proposed PMA shows an absorption peak with almost 100% absorptivity at 6.2 GHz. Also, wideband negative index of refraction is observed. Further, the absorber is inspected for the different rotation angles of the top metasurface (omega-shaped ring) along the optical axis, and obliquity of incidence angle for both TE and TM polarized waves. Moreover, surface electric field and surface current...
Formal process algebraic modeling, verification, and analysis of an abstract Fuzzy Inference Cloud Service
, Article Journal of Supercomputing ; Vol. 67, issue. 2 , February , 2014 , pp. 345-383 ; Online ISSN: 1573-0484 ; Rahmani, A. M ; Movaghar, A ; Teshnehlab, M
2014
Abstract
In cloud computing, services play key roles. Services are well defined and autonomous components. Nowadays, the demand of using Fuzzy inference as a service is increasing in the domain of complex and critical systems. In such systems, along with the development of the software, the cost of detecting and fixing software defects increases. Therefore, using formal methods, which provide clear, concise, and mathematical interpretation of the system, is crucial for the design of these Fuzzy systems. To obtain this goal, we introduce the Fuzzy Inference Cloud Service (FICS) and propose a novel discipline for formal modeling of the FICS. The FICS provides the service of Fuzzy inference to the...
Impact of holmium on structural, dielectric and magnetic properties of Cu–Zn spinel ferrites synthesized via sol–gel route
, Article Journal of Materials Science: Materials in Electronics ; Volume 32, Issue 2 , 2021 , Pages 2205-2218 ; 09574522 (ISSN) ; Khan, M. A ; Hussain, A ; Akhtar, M. N ; Ahmad, M ; Javid, M. A ; Sharif University of Technology
Springer
2021
Abstract
The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to...
Impact of holmium on structural, dielectric and magnetic properties of Cu–Zn spinel ferrites synthesized via sol–gel route
, Article Journal of Materials Science: Materials in Electronics ; Volume 32, Issue 2 , 2021 , Pages 2205-2218 ; 09574522 (ISSN) ; Khan, M. A ; Hussain, A ; Akhtar, M. N ; Ahmad, M ; Javid, M. A ; Sharif University of Technology
Springer
2021
Abstract
The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to...
An experimental study on mechanical behavior of a calcite cemented gravelly sand
, Article Geotechnical Testing Journal ; Volume 41, Issue 3 , May , 2018 , Pages 494-507 ; 01496115 (ISSN) ; Haeri, S. M ; Shahrabi, M. M ; Khosravi, A ; Sajadi, A. A ; Sharif University of Technology
ASTM International
2018
Abstract
In the study presented herein, a simple method for laboratory calcite cementation of a reconstituted gravelly sand was presented. This method was used to prepare cemented gravelly sand specimens, which have similar natural characteristics to alluvial deposit of the city of Tehran. The formation and distribution of calcite bonds, as well as the effectiveness of the presented calcite cementation method in increasing interparticle cohesion, as observed in weakly to moderately cemented soil in Tehran, were evaluated by means of chemical analysis, X-ray diffraction technique, and unconfined compressive strength tests. The cementation technique was used to prepare triaxial specimens with calcite...
A new dynamic optimal m2m rf interface setting in relay selection algorithm (dorsa) for iot applications
, Article IEEE Access ; Volume 10 , 2022 , Pages 5327-5342 ; 21693536 (ISSN) ; Hemmatyar, A. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Machine-to-Machine (M2M) communication is an important type of communication in the Internet-of-Things (IoT). How to send data in these high-density communications using relay selection can help improve the performance of this type of communication in various applications. In addition, the possibility of simultaneous use of different Radio Frequency (RF) interfaces helps to use the spectrum more efficiently. In this work, we try to further use machine communication RF equipment and improve the average data rate of networks in some applications such as the IoT, which have their own bandwidth requirements. Therefore, we provide an optimization algorithm for relay selection as well as the...
P-V-L Deep: A big data analytics solution for now-casting in monetary policy
, Article Journal of Information Technology Management ; Volume 12, Issue 4 , 2021 , Pages 22-62 ; 20085893 (ISSN) ; Kazemi, M. A ; Alborzi, M ; Azar, A ; Kermanshah, A ; Sharif University of Technology
University of Tehran
2021
Abstract
The development of new technologies has confronted the entire domain of science and industry with issues of big data's scalability as well as its integration with the purpose of forecasting analytics in its life cycle. In predictive analytics, the forecast of near-future and recent past - or in other words, the now-casting - is the continuous study of real-time events and constantly updated where it considers eventuality. So, it is necessary to consider the highly data-driven technologies and to use new methods of analysis, like machine learning and visualization tools, with the ability of interaction and connection to different data resources with varieties of data regarding the type of big...
Spray characteristics and atomization behavior of bio-diesel (Norouzak) and diesel fuel blends
, Article Particulate Science and Technology ; 2016 , Pages 1-12 ; 02726351 (ISSN) ; Jafari, M ; Ahari, M ; Saidi, M. H ; Hajinezhad, A ; Mozaffari, A. A ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
Norouzak oil seeds that are the source of bio-diesel (Norouzak) fuel grow mostly in Gonabad and Kashmar located in Khorasan, north east of Iran. Spray characteristics of Norouzak bio-diesel have been experimentally and theoretically studied in this work. Norouzak fuel is added to the conventional diesel fuel, and mixture formations of several blends have been investigated and compared with each other. Moreover, by varying ambient and injection conditions, behaviors of spray of different blends have been explored. Microscopic and macroscopic properties of spray such as Sauter Mean Diameter (SMD), Ohnesorge number, spray tip penetration, spray cone angle, spray projected area and volume have...
Spray characteristics and atomization behavior of bio-diesel (Norouzak) and diesel fuel blends
, Article Particulate Science and Technology ; Volume 36, Issue 3 , 2018 , Pages 270-281 ; 02726351 (ISSN) ; Jafari, M ; Ahari, M ; Saidi, M. H ; Hajinezhad, A ; Mozaffari, A. A ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Norouzak oil seeds that are the source of bio-diesel (Norouzak) fuel grow mostly in Gonabad and Kashmar located in Khorasan, north east of Iran. Spray characteristics of Norouzak bio-diesel have been experimentally and theoretically studied in this work. Norouzak fuel is added to the conventional diesel fuel, and mixture formations of several blends have been investigated and compared with each other. Moreover, by varying ambient and injection conditions, behaviors of spray of different blends have been explored. Microscopic and macroscopic properties of spray such as Sauter Mean Diameter (SMD), Ohnesorge number, spray tip penetration, spray cone angle, spray projected area and volume have...
Experimental and theoretical investigations on spray characteristics of bio-ethanol blends using a direct injection system
, Article Scientia Iranica ; Volume 24, Issue 1 , 2017 , Pages 237-248 ; 10263098 (ISSN) ; Jafari, M ; Ahari, M ; Saidi, M. H ; Hajinezhad, A ; Mozafari, A. A ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
In the present work, the spray characteristics of bio-ethanol and its blends have been experimentally and theoretically investigated. To have a comprehensive study, the effects of ambient condition and injection pressure on the spray of different blends have been considered. Macroscopic and microscopic characteristics of spray such as tip penetration length, cone angle, projected area, volume, Sauter Mean Diameter (SMD), and Ohnesorge number are investigated precisely. Besides, air entrainment and atomization analyses have been carried out to improve mixture formation process. Using curve fitting and least squares method, theoretical correlations have been suggested in such a way to predict...
Utilisation of knowledge management in decreasing waste of steel structure construction via increasing effectiveness of welding process
, Article Association of Researchers in Construction Management, ARCOM 2009 - Proceedings of the 25th Annual Conference, 7 September 2009 through 9 September 2009 ; 2009 , Pages 759-768 ; 095523901X (ISBN) ; 9780955239014 (ISBN) ; Hajikarimi, A. A ; Ghalambor, M. A ; Sharif University of Technology
2009
Abstract
As firms are facing with a new competitive environment which knowledge has a unique position, they should give more consideration to their employer's knowledge, and construction firms are not an exception. Employers are creating values for companies, and nowadays they are counted as strategic resources. In construction firms, due to their project based nature, workers are more important in creating values. One of the most essential elements of a construction firm is its ability to cope with social and environmental pressures to reduce waste and minimise the use of raw materials. To decrease wastes of Steel structure Construction, it is necessary to enhance the weld quality. Weld quality...