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A study of endurance time method in the analysis of elastic moment frames under three-directional seismic loading
, Article Asian Journal of Civil Engineering ; Volume 11, Issue 5 , 2010 , Pages 543-562 ; 15630854 (ISSN) ; Estekanchi, H ; Sharif University of Technology
2010
Abstract
Endurance Time (ET) method is a time history based analysis procedure that applies special intensifying acceleration functions for estimating the seismic performance of structures at different excitation levels in each single analysis. One of the extensions of the ET method is in the seismic assessment of buildings considering multi-component excitation. In this paper, a procedure for three-directional seismic analysis of buildings is proposed and application of this method to several steel moment frames is investigated. Several Steel Moment Frames were designed according to INBC Code. These Frames were analyzed under ET acceleration functions in horizontal and vertical directions...
Three Dimensional Non-Linear Seismic Analyses of Buildings, Using Endurance Time Method
, Ph.D. Dissertation Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
Endurance Time Method (ET) is a type of dynamic pushover procedure in which the structure is analyzed under special series of accelerograms, called ET acceleration Functions (ETAF) and the response of structure is sketched versus time until the collapse state. With evaluating response curve and the time which damage in structure reach the expected value, the final assessment of structure can be made. In this dissertation, the application of ET method for Non-linear 3 dimensional seismic analysis of steel moment frames under earthquake multicomponent excitation is investigated. For this purpose, various patterns of ET loading are investigated and the most appropriate algorithm in...
Multi-Directional Seismic Analysis and using ET Method in Estimation of the Results
,
M.Sc. Thesis
Sharif University of Technology
;
Esmaeil Pourestekanchi, Homayun
(Supervisor)
Abstract
Exact and safe structural analysis and design under various loadings is an important issue, which have engaged engineers for a long time. Till now, building design codes have suggested three main methods for seismic analysis of structures, which consist of: Static analysis, Pseudo-dynamic response spectrum analysis and Time history analysis. The first two methods are too approximate, especially in irregular structures which demand exact 3d analyses. The most reliable method is Time history method. With advance of computational tools, engineers tend toward using more reliable analysis methods and using old fashioned rough methods is becoming less popular. One of the issues, which is important...
Modeling of dislocation density and strength on rheoforged A356 alloy during multi-directional forging
, Article Computational Materials Science ; Vol. 81 , 2014 , pp. 284-289 ; Saei, M ; Kazeminezhad, M ; Dodangeh, A ; Sharif University of Technology
Abstract
In this study, a hybrid model is presented to predict the dislocation density and strength evolution of the rheoforged non-dendritic A356 alloy during multi-directional forging. Regarding the characteristics of non-dendritic A356 alloy, combination of Shear Lag and Nes models is used for the eutectic structure, and Nes model is used for the α-Al globular phase. The aspect ratio variations of Si particles in eutectic structure during 3 passes of multi-directional forging do not change the model predictions, significantly. Model predictions on shear stress are in good agreement with experimental results of shear punch test
Multi-directional spatial error concealment using adaptive edge thresholding
, Article IEEE Transactions on Consumer Electronics ; Volume 58, Issue 3 , 2012 , Pages 880-885 ; 00983063 (ISSN) ; Rabiee, H ; Pourdamghani, N ; Ghanbari, M ; Sharif University of Technology
2012
Abstract
In this paper, a new method for spatial concealment of missing areas in image and video signals transmitted over error prone infrastructures, is presented. The concealment process is performed in three steps. First, a novel technique is used to estimate the significant edges of missing areas after performing a directional edge analysis on the correctly received neighboring blocks of the missing areas. This technique uses the moments of the neighboring edge magnitudes to obtain an adaptive threshold for rejecting non-significant directions. Second, based on the predicted significant directions, an approximation is obtained for each missing pixel. Finally, for each pixel, we compute a weighted...
On the solution treatment of severely deformed AA2024-O and subsequent natural aging
, Article Journal of Materials Research and Technology ; Volume 20 , 2022 , Pages 1558-1569 ; 22387854 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Elsevier Editora Ltda
2022
Abstract
In this research, the effect of applying severe strain before solid solution treatment (SST) for AA2024-O was studied. Providing concurrent insights into solutionizing behavior and microstructural evolution corresponding to hardness is important. Multi-directional forging (MDF) was used as a severe plastic deformation (SPD) method. After applying SST on MDFed (4 passes) and as-annealed samples, natural aging (NA) was used as the following treatment to examine the role of severe strain on the solutionizing behavior. In most previous attempts, SPD has been used after SST, but one of the innovations of the present work is the study of SPD before SST. Experimental results show that adding a...
Investigating the Behavior of 3D Irregular Steel Structures with Seismic Base Isolation under Multi-Directional Excitations and Predicting Results by Using the Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmail Pourestekanchi, Homayoon (Supervisor)
Abstract
This research has been performed with the aim of gaining familiarity with various types of seismic isolation systems, their unique features and numerous advantages, factors affecting their performance and finally their modelling and design. Despite the advantages of seismic isolation systems as control instruments, but where there is not enough information on the involved parameters in the performance of these systems, there is possibility of unpredictable behavior of the structures. Hence, considering the extent and influence of each parameter involved in the performance of the isolators, a parametric study is performed utilizing the 3D models under multi-directional excitations, using the...
Effect of concurrent precipitation on the texture evolution during continuous heating of multi directionally forged solution treated Al-Cu-Mg alloy
, Article Materials Characterization ; Volume 131 , 2017 , Pages 399-405 ; 10445803 (ISSN) ; Kazeminezhad, M ; Logé, R ; Sharif University of Technology
Abstract
Concurrent precipitation in an age hardenable aluminum alloy determines recrystallization behavior especially grains structure and recrystallization texture during continuous heating. In this study, to investigate the effect of concurrent precipitation on the recrystallization texture and grains structure, a solution treated Al-Cu-Mg alloy has been multi-directionally forged at room temperature and continuously heated with different heating rates (800, 1600 and 2500 K·min− 1) up to 450 °C using Gleeble 3800 thermo-mechanical simulator. At lower heating rates (800 K·min− 1), Goss texture component {110} 〈001〉 (Φ1 = 90°/0°, Φ = 90°/45°, Φ2 = 45°/90°) is developed during continuous heating and...
The effect of strain rate on multi-directional forged aluminum: examining the experimental data and modeling results
, Article Materials Chemistry and Physics ; Volume 239 , 1 January , 2020 ; Kazeminezhad, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, multi-directional forging (MDF) as a severe plastic deformation method, annealing, and compression test at different strain rates are applied on pure aluminum. One of the main observations is when the number of MDF passes is increased, the hardness is risen. The most noticeable reduction in hardness occurs when the MDFed samples are annealed at 350 and 450 °C. Moreover, increasing the number of MDF passes and the strain rate of the compression test cause the increase in the yield stress of the samples. If the MDFed samples are non-annealed or if they are annealed at a maximum temperature of 250 °C, the effect of an increase in the number of passes on the yield stress is more...
Compatibility of the endurance time method with codified seismic analysis approaches on three-dimensional analysis of steel frames
, Article Structural Design of Tall and Special Buildings ; Volume 22, Issue 2 , 2013 , Pages 144-164 ; 15417794 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
2013
Abstract
The endurance time (ET) method is a time history-based dynamic pushover analysis procedure that utilizes special intensifying acceleration functions for estimating the seismic performance of structures at different excitation levels. One of the potential applications of the ET method is in the three-dimensional analysis of buildings considering multidirectional excitation. In this paper, a procedure for multi-component analysis by the ET method has been developed. Several steel moment frames with heights from 9.6 to 48 m were designed according to the Iranian National Building Code. By applying the proposed algorithm for three-dimensional analysis of structures by the ET method, these frames...
Signal extrapolation for image and video error concealment using gaussian processes with adaptive nonstationary kernels
, Article IEEE Signal Processing Letters ; Volume 19, Issue 10 , 2012 , Pages 700-703 ; 10709908 (ISSN) ; Rabiee, H. R ; Rohban, M. H ; Sharif University of Technology
IEEE
2012
Abstract
In this letter, a new adaptive Gaussian process (GP) frame work for signal extrapolation is proposed. Signal extrapolation is an essential task in many applications such as concealment of corrupted data in image and video communications. While possessing many interesting properties, Gaussian process priors with inappropriate stationary kernels may create extremely blurred edges in concealed areas of the image. To address this problem, we propose adaptive non-stationary kernels in a Gaussian process framework. The proposed adaptive kernel functions are defined based on the hypothesized edges of the missing areas. Experimental results verify the effectiveness of the proposed method compared to...
Endurance time method for multi-component analysis of steel elastic moment frames
, Article Scientia Iranica ; Volume 18, Issue 2 A , 2011 , Pages 139-149 ; 10263098 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Abstract
The Endurance Time (ET) method is a time history-based dynamic analysis procedure which uses special intensifying acceleration functions for evaluation of the seismic response of structures. One of the potential applications of the ET method is in the three-dimensional analysis of buildings under multidirectional excitations. In this paper, considering horizontal components of excitation, an algorithm for the multi-component analysis of building structures by the ET method is proposed, and results of the ET method for various steel moment frames with 1 to 7 stories are compared with results from time history analysis with real earthquakes. Results show that based on recommendations of...
Multi-directional response of unreinforced masonry walls: experimental and computational investigations
, Article Earthquake Engineering and Structural Dynamics ; Volume 45, Issue 9 , 2016 , Pages 1427-1449 ; 00988847 (ISSN) ; Aref, A. J ; Sharif University of Technology
John Wiley and Sons Ltd
2016
Abstract
This paper describes the results of an experimental and numerical study that focused on multi-directional behavior of unreinforced masonry walls and established the requisite of the related proposed design equations. The tests were conducted following several sets of multi-directional loading combinations imposed on the top plane of the wall along with considering monotonic and cyclic quasi-static loading protocols. Various boundary conditions, representing possible wall–roof connections, were also considered for different walls to investigate the influence of rotation of the top plane of the wall on the failure modes. The results of the tests were recorded with a host of high precision data...
Heating rate effect on particle stimulated nucleation and grains structure during non-isothermal annealing of multi-directionally forged solution treated AA2024
, Article Materials Characterization ; Volume 127 , 2017 , Pages 317-324 ; 10445803 (ISSN) ; Kazeminezhad, M ; Logé, R ; Sharif University of Technology
Elsevier Inc
2017
Abstract
Particle stimulated nucleation (PSN) is one of the important mechanisms of recrystallization which is investigated in this research during non-isothermal annealing of multi-directionally forged solution treated aluminum alloy 2024. Non-isothermal annealing is performed up to temperatures of 380 °C and 450 °C at heating rates of 10, 100 and 200 K·min− 1 using a Gleeble 3800 thermo-mechanical simulator. In order to investigate the microstructure, field emission gun scanning electron microscope (FEG-SEM) equipped with electron backscatter diffractometer (EBSD) and differential scanning calorimetry (DSC) are utilized. The results show that the heating rate has a significant effect on the PSN and...
Mechanical behavior and texture development of over-aged and solution treated Al-Cu-Mg alloy during multi-directional forging
, Article Materials Characterization ; Volume 135 , 2018 , Pages 221-227 ; 10445803 (ISSN) ; Kazeminezhad, M ; Logé, R ; Sharif University of Technology
Elsevier Inc
2018
Abstract
The effects of initial heat treatments, i.e. solution treating and over ageing, on deformation behavior of an age hardenable Al-Cu-Mg alloy, including mechanical properties and texture evolution, during multi-directional forging (MDF) are investigated. Hardness measurements, electron back scatter diffraction (EBSD) maps, and differential scanning calorimetry (DSC) are carried out. Mechanical behaviors of the alloy in terms of compressive stress and hardness test after MDF are investigated. In both solution treated and over-aged alloys, the compressive stress during MDF shows an increase up to the second pass, and by further straining the flow stress is decreased. However, shear and...
Effects of non-isothermal annealing on microstructure and mechanical properties of severely deformed aluminum samples: Modeling and experiment
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 29, Issue 6 , 2019 , Pages 1127-1137 ; 10036326 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Nonferrous Metals Society of China
2019
Abstract
In order to investigate the evolution of microstructure and flow stress during non-isothermal annealing, aluminum samples were subjected to strain magnitudes of 1, 2 and 3 by performing 2, 4 and 6 passes of multi-directional forging. Then, the samples were non-isothermally annealed up to 150, 200, 250, 300 and 350 °C. The evolution of dislocation density and flow stress was studied via modeling of deformation and annealing stages. It was found that 2, 4 and 6 passes multi-directionally forged samples show thermal stability up to temperatures of 250, 250 and 300 °C, respectively. Modeling results and experimental data were compared and a reasonable agreement was observed. It was noticed that...
Flow stress of 2024 aluminum alloy during multi-directional forging process and natural aging after plastic deformation
, Article Materials Chemistry and Physics ; Volume 254 , 2020 ; Kazeminezhad, M ; Shadkam, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The hardening behavior of heat treatable alloys during deformation is attributed to three mechanisms of forest dislocations, solid solution and precipitation hardening which hinder the motion of dislocations and increase the density of statistically stored dislocation. In this paper, a model for the flow stress of a 2024 heat treatable aluminum alloy during plastic deformation is developed combining the superposition of these three hardening mechanisms. This model was then implemented into the finite element model in order to evaluate the evolution of the flow stress of 2024 aluminum alloy during multi-directional forging (MDF). Subsequently, an equation is developed for evaluating the...
Improved corrosion resistance and mechanical properties of biodegradable Mg-4Zn-xSr alloys: effects of heat treatment, Sr additions, and multi-directional forging
, Article Journal of Materials Research and Technology ; Volume 20 , 2022 , Pages 3363-3380 ; 22387854 (ISSN) ; Alizadeh, R ; Mahmudi, R ; Sharif University of Technology
Elsevier Editora Ltda
2022
Abstract
The effects of Sr additions, heat treatment (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biodegradability of Mg-4Zn-xSr alloys were investigated. Corrosion behavior of the alloys was evaluated by the polarization and hydrogen evolution tests. Shear punch and hardness tests were employed to determine the mechanical properties. It was found that mechanical properties and corrosion resistance of the as-cast Mg-4Zn alloy increased by 0.3 wt% Sr addition. However, further increasing the Sr content not only did not improve the mechanical strength, but also had detrimental effects on the corrosion resistance, due to the increased size and...
Coanda surface geometry optimization for multi-directional co-flow fluidic thrust vectoring
, Article Proceedings of the ASME Turbo Expo: Power for Land, Sea, and Air ; Volume 5 , 2009 , Pages 183-189 ; 9780791848869 (ISBN) ; Banazadeh, A ; Sharif University of Technology
Abstract
The performance of Co-flow fluidic thrust vectoring is a function of secondary flow characteristics and the fluidic nozzle geometry. In terms of nozzle geometry, wall shape and the secondary slot aspect ratio are the main parameters that control the vector angle. The present study aims to find a high quality wall shape to achieve the best thrust vectoring performance, which is characterized by the maximum thrust deflection angle with respect to the injected secondary air. A 3D computational fluid dynamics (CFD) model is employed to investigate the flow characteristics in thrust vectoring system. This model is validated using experimental data collected from the deflection of exhaust gases of...