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seismic-response
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Investigating the Feasibility of using Magnetic Field in Seismic Response Control of Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor) ; Kazemi, Mohammad Taghi (Supervisor) ; Ghorbani Vaghei, Bahman (Co-Advisor)
Abstract
Base isolation is a method for controlling the vibration of structure by modifying the transmission between the source of excitation and the vibration structure.In this thesis, the feasibility of using magnetic field in seismic response control of structures has been investigated. It is tried with the inspiration of magnetic trains. While the old trains ran on the rail lost a large amount of energy because of the friction between the wheels and the rails that decreased the train speed, in the maglev trains with separating them from the rail the friction is reduced to the least amount so that today these trains are able to run with the speed about 550 km/h. It has been tried in two concepts...
A state-of-knowledge review on the endurance time method
, Article Structures ; Volume 27 , 2020 , Pages 2288-2299 ; Mashayekhi, M ; Vafai, H ; Ahmadi, G ; Mirfarhadi, S. A ; Harati, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The endurance time method is a time history dynamic analysis in which structures are subjected to predesigned intensifying excitations. This method provides a tool for response prediction that correlates structural responses to the intensity of earthquakes with a considerably less computational demand as compared to conventional time history analysis. The endurance time method is being used in different areas of earthquake engineering, such as performance-based assessment and design, life-cycle cost-based design, value-based design, seismic safety, seismic assessment, and multi-component seismic analysis. Successful implementation of the endurance time method relies heavily on the quality of...
Impact of seismic excitation characteristics on the efficiency of tuned liquid column dampers
, Article Earthquake Engineering and Engineering Vibration ; Volume 5, Issue 2 , 2006 , Pages 235-243 ; 16713664 (ISSN) ; Zahrai, M ; Sharif University of Technology
2006
Abstract
Various types of passive control systems have been used to suppress the seismic response of structures in recent years. Among these systems, Tuned Liquid Column Dampers (TLCDs) dissipate the input earthquake energy by combining the effects of the movement of the liquid mass in the container, the restoring force on the liquid due to the gravity loads and the damping due to the liquid movement through orifices. In this study, the effects of seismic excitation characteristics such as frequency content and soil condition on the seismic performance of TLCDs are investigated using nonlinear time-history analyses. In this regard, among the past earthquake ground motion records of Iran, 16 records...
Quantifying seismic response uncertainty of electrical substation structures using endurance time method
, Article Structures ; Volume 30 , 2021 , Pages 838-849 ; 23520124 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
A new procedure is proposed to quantify uncertainties involved in the seismic response of structures including ground motion and modeling variability. The advent of performance-based earthquake engineering (PBEE) and probabilistic seismic risk analysis necessitates consideration of uncertainties in predicting seismic responses. However, the high computational cost of conventional methods restricts their application to only simple numerical models. The present study employs the endurance time (ET) method concept to predict the response distribution which requires much less computational efforts than conventional methods. The proposed procedure for the quantification of record-to-record...
Predicting probabilistic distribution functions of response parameters using the endurance time method
, Article Structural Design of Tall and Special Buildings ; Volume 28, Issue 1 , 2019 ; 15417794 (ISSN) ; Mirfarhadi, A ; Esmail Pour Estekanchi, H ; Vafai, H ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
The main objective of this study is the development of endurance time (ET) excitations in order to take structural response uncertainty into account for use in performance-based earthquake engineering. There are several uncertainties in earthquake engineering, including earthquake occurrence, structural response, damage, and loss. In the current research, structural response uncertainty is directly included in the ET method, which is an analysis method used for performing structural behavior assessment under seismic actions. Conventional practice of the ET method does not provide any information about seismic response distribution. Despite the simplicity of the ET method, it is an accurate...
Predicting probabilistic distribution functions of response parameters using the endurance time method
, Article Structural Design of Tall and Special Buildings ; Volume 28, Issue 1 , 2019 ; 15417794 (ISSN) ; Mirfarhadi, S. A ; E. Estekanchi, H ; Vafai, H ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
The main objective of this study is the development of endurance time (ET) excitations in order to take structural response uncertainty into account for use in performance-based earthquake engineering. There are several uncertainties in earthquake engineering, including earthquake occurrence, structural response, damage, and loss. In the current research, structural response uncertainty is directly included in the ET method, which is an analysis method used for performing structural behavior assessment under seismic actions. Conventional practice of the ET method does not provide any information about seismic response distribution. Despite the simplicity of the ET method, it is an accurate...
Dynamic Analysis and Liquefaction Evaluation of Earth Dams, Mahabad Dam case Study
,
M.Sc. Thesis
Sharif University of Technology
;
Jafarzadeh, Fardin
(Supervisor)
Abstract
Liquefaction due to the earthquake loading is one of the most important threats in the earth structure. Analysis of liquefaction of structures such as dam/foundation systems utilizing numerical methods such as finite difference and finite element, can considerably determine the real response of the structures during strong ground motions. Mahabad rockfill dam, located in upper vicinity of Mahabad city, in North-West of Iran, completed and impounded in 1970. This embankment dam was designed as a zoned dam with a slightly inclined impervious clay core and 47.5 m in height. Studying such structures, which have been designed with simple methods in olden times, can recognize the potential risks...
Predicting probabilistic distribution functions of response parameters using the endurance time method
, Article Structural Design of Tall and Special Buildings ; 2018 ; 15417794 (ISSN) ; Mirfarhadi, S. A ; Esmaeilpour Estekanchi, H ; Vafai, H ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
The main objective of this study is the development of endurance time (ET) excitations in order to take structural response uncertainty into account for use in performance-based earthquake engineering. There are several uncertainties in earthquake engineering, including earthquake occurrence, structural response, damage, and loss. In the current research, structural response uncertainty is directly included in the ET method, which is an analysis method used for performing structural behavior assessment under seismic actions. Conventional practice of the ET method does not provide any information about seismic response distribution. Despite the simplicity of the ET method, it is an accurate...
Evaluation of variable permeability model in simulation of seismic behavior of uniform level and gently sloping sand layers
, Article Earth Sciences Research Journal ; Volume 24, Issue 3 , 2020 , Pages 328-336 ; Seyfi, S ; Shahir, H ; Sharif University of Technology
Universidad Nacional de Colombia
2020
Abstract
In this study, a fully coupled dynamic finite element model was employed for numerical simulation of the response of level to gently sloping saturated sand layers subjected to cyclic loading. This model utilized a critical state two-surface-plasticity constitutive model to simulate the cyclic behavior of sandy soil. Moreover, a recently proposed variable permeability function was implemented in the numerical model to reflect the effects of soil permeability variations during the liquefaction phenomenon. The numerical model was validated by simulating a number of well-documented geotechnical centrifuge tests with different relative density of sand, base acceleration time history, and surface...
On the Base Shear Force Distribution Along the Height of Base-Isolated Structures With LRB Isolators Subjected to Near Field Earthquakes
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
In recent years there has been a huge amount of attention in the application of the base isolation system as a passive procedure to limit seismic response of structures. A number of international codes including UBC97, ASCE07-2005, and ASCE-2010 have devoted a special part for the Seismic analysis and design of base-isolated structures. The present work investigates the vertical distribution of the lateral seismic force, for base-isolated structures suggested by the ASCE07_05 code under near field earthquakes. Near field earthquakes have attracted so much interest among the researchers and engineers due to their disastrous effects on structures. According to the recorded data, it is...
Investigating the Performance of Friction Dampers with Variable Slip Loads Together with the SMA Materials to Control the Seismic Response of Steel Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
The parallel combination of friction damper with shape memory alloys has been proposed as a self-centering friction damper (SFDB) in the past. The aim of this study is to improve the performance of the SFDB as M-SFDB and investigate its effect on seismic responses of steel moment resisting structures. The basic idea used in the proposed M-SFDB damper is to create sloped surfaces and using SMA bolts to change the slip load of friction during the loading and unloading cycles. In order to evaluate the effect of the proposed mechanism, four types of 4, 8 and 12-story structures located on site classes B and D are designed using ASCE_7-10 and AISC_360-10 codes. These structural models include...
Investigating the Performance of Dual Slip Load Friction Dampers in Reducing the Seismic Response of Steel Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
In this research, the performance of a new friction damper with two different slip loads to improve the seismic response of steel structural models is investigated. Also, different slip loads are considered in different floors to reduce the response parameters such as story drifts, permanent story drifts, absolute floor accelerations, and base shear forces. In this regard and as the first step, three steel moment resisting frame models with 4, 8 and 12 number of stories are designed using the AISC-LRFD and ASCE 7-10 codes. Then, the effects of slip load changes of the two level friction dampers on the seismic response of the structural models were investigated and the domain of the slip...
Numerical Study of Pile Behavior under Seismic Loading
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mahdi (Supervisor)
Abstract
Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of...
The Study of Soild Slope Seismic Response using the Physical Model Test on the Shaking Table
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Evaluation of seismic slope stability is very important because it has a decisive role in estimating the earthquake damages. According to the past studies medium to large earthquakes, usually cause thousands landslides and many casualties and financial damages. Since nearly half a century ago, several methods have been developed for predicting the occurrence of landslides and permanent movements, but due to the influence of many parameters on the seismic stability of the slopes further researches is needed.In present study, to investigate the dynamic behavior of the slopes, three physical models of slopes had been made on shaking table in Sharif University of technology. These slopes have...
Evaluation of the Performance of Viscoelastic Dampers in Controlling the Seismic Induced Response of Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
In the present study, the performance of Viscoelastic Dampers in reducing the seismic response of the structures was investigated. For this purpose, first the effect of added damping to the system was studied. Number of 3-D steel structural models, with and without eccentricity which are designed with the 2800 code (first edition) and 519 code provisions that is not satisfied the provisions of the code-2800(third edition) is considered. It is assume that this system is located on a relatively stiff soil (soil type II based on Iranian Seismic Standard Code - 2800), a number of compatible earthquake records also considered to be used in the parametric studies. The results indicate that 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...
Numerical Modeling of Piles under Seismic Excitation
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
In safe and economic designing of deep foundations for any structure, there are several factors affecting the behavior and response of a pile under seismic loads. These factors can be divided into three main categories: geometrical factors (e.g. Dimensions of the pile, soil, and mesh scheme), material properties (e.g. shear modulus, bulk modulus, soil elasticity, soil density, and shear strength) and earthquake load characteristics (e.g. frequency range, PGA, duration of excitation(. Studying the effects and importance of these factors in the final response of the pile (i.e. ultimate forces and displacements ) can help the design engineers of these foundations to optimize their designs....
Investigation of Seismic Response of Circular-Plan Concrete Funicular Shells
, M.Sc. Thesis Sharif University of Technology ;
Abstract
The present study considers the performance of circular-plan concrete funicular shells due to seismic loads for simply boundary conditions. Vibration frequencies of these shells along with their seismic responses included displacement and stresses generated in them due to the acceleration components of Tabas and Manjil earthquakes are determined via the use Abaqus software. Frequencies of vibration determined with software are compared with the results of a semi-analytical model where good agreement is achieved.The results of the performed analyses for vibration frequencies show that both of the reduction of the base diameter and the incerese of the rise increase the frequencies of...
Seat width requirement for skewed bridges under seismic loads
, Article Scientia Iranica ; Vol. 21, issue. 5 , 2014 , pp. 1471-1479 ; ISSN: 10263098 ; Bagheri, S ; Sharif University of Technology
Abstract
In this paper, the dynamic characteristics of skewed bridges are explored analytically. Closed form solutions for translational and torsional periods of free vibration and mode shapes are given for slab-girder skewed bridges. Moreover, the seismic displacement of the deck of skewed bridges is calculated using the response spectrum method and its skew term is compared with the requirement of AASHTO. The effects of seismic force resisting elements, such as elastomeric bearings and end diaphragms are included. It is shown that the skew term in AASHTO's equation can underestimate the seat width requirement for some bridges. A new skew term for the bridge seat width requirement is suggested
Experimental investigation of steel frames with single bays of symmetrical y-shaped concentric bracings
, Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 195-210 ; 10263098 (ISSN) ; Vafai, A ; Aghakouchak, A. A ; Kazemi, M. T ; Sharif University of Technology
2012
Abstract
To obtain wider openings than those provided by Chevron bracing, the braces are cranked and connected to the frame corner by an additional brace to form double y-shaped bracings. However, y-bracings are prone to instability and out of plane buckling, accompanied by low hysteretic energy absorption. An experimental research program, focused on y-bracing, was conducted at the BHRC structural engineering laboratory. Specimens presented in this paper include three full-scale single bay frames, with symmetric y-bracing of different cross sections and connection types. In addition, one specimen with Chevron bracing was tested as a reference. A quasi-static cyclic loading was applied increasingly...