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    Analytical and Experimental Study of Isolation of Sensitive Equipments from Ambient Vibrations

    , M.Sc. Thesis Sharif University of Technology Mahvash Mohammadi, Akbar (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    In some activities, an almost free of any vibration environment is needed. Semi conductor production process and microelectronic microscopes are two examples in which a quiet environment is essential. The goal of this thesis is to attenuate ambient vibrations effectively and to prepare a suitable environment for two microelectronic microscopes. The designed system must be practical, economical and capable of being made in a short time interval. Considering mentioned properties a steel table with bolt connections supported on 4 air springs was built. To investigate dynamic properties, modal analysis was performed with the aid of finite element packages and experiments. To extract oscillations... 

    Random Vibration Analysis for Multi-Story Base Isolated Structures

    , M.Sc. Thesis Sharif University of Technology Mehdizadeh Nasrabadi, Mohammad (Author) ; Bakhshi, Ali (Supervisor)
    Abstract

    Earthquake motions are among random excitation loads. For that we used random vibration approach to estimate response of multi-degree of freedom base isolated structures under ground excitation. Some models including linear model ,nonlinear Bouc-Wen and BBW models are studied for modeling the superstructure .Several base isolation models including the laminated rubber bearing, high damping laminated rubber bearing ,resilient-friction base isolator with or without sliding upper plate and the Electricity de France system, are studied . El Centro 1940 and Mexico City 1985 earthquake which preserve the nonstationary evolutions of amplitude and frequency content of ground accelerations... 

    Loading Pattern and Spatial Distribution of Wind Load and Comparison of Wind and Earthquake Effects along the Height of Tall Buildings

    , M.Sc. Thesis Sharif University of Technology Nikbakht, Hamed (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    In the ongoing research project on tall buildings, the study of wind-induced demands is categorized as: along-wind and crosswind responses. These demands are caused by different mechanisms. Moving along the wind-induced is due to the effects of turbulence impact while the perpendicular component is related to the effects of windstorm. Along-wind response may be of special importance with respect to the comfort criteria. The loading condition on skyscrapers may differ from low-rise buildings due to the number of stories, on structures due to the high number of stories, and the importance of dynamic effects of current loading (wind). On the other hand the effect of wind load on tall structures... 

    Method of Estimating the Response Modification Factor for Stiffened Steel Shear Wall Systems

    , M.Sc. Thesis Sharif University of Technology Aslani, Jalal (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Steel shear wall systems have been introduced as a lateral load resisting system since 1970s. Based on the designer’s choice, this system can be used with or without stiffeners. Employing stiffeners prevents the elastic buckling of steel plates which can enhance the system to absorb more energy. The design code for using stiffners has not developed yet in Iran since this kind of systems is not common practice. In this study, the Response Modification Factor (R), as an important factor in the design procedures of structures, is investigated for 2 to 10-story building structures which have steel shear walls with 3 and 6 millimeters thickness with 3, 4 and 6 meters spans.To this end, the... 

    Study on Base Isolation Codes and New Regulation Proposal

    , M.Sc. Thesis Sharif University of Technology Nabavi, Vahid (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Seismic isolation is a method for seismic-resistant design of structures against earthquake and is one of the important control of structures technologies. Codification and publishing of codes for design of seismic isolation takes place widely since 1980s and this codification has undergone extensive evolutions during its developing process. In this project initially the developing process and fundamentals of codifying regulations of seismic design have been investigated and then the developing process of codifying regulations of seismic isolation in current important international codes like ASCE7-05, Eurocode 8, and Japanese code has also been considered. After considering these two... 

    Dynamic Effects of Wind and Earthquake Loads on Tall Buildings Using Probabilistic Approach

    , M.Sc. Thesis Sharif University of Technology Nakhostin, Elham (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Tall buildings with lightweight and low damping are vulnerable under wind load. The wind loads stimulate tall buildings in the alongwind and acrosswind direction so the wind loads should be considered in addition to the earthquake loads. Wind tunnel testing is one of the empirical testing that used to study the behavior of tall buildings under wind load besides the simulation of turbulence components of the wind field is one of the issues that have been studied by researchers. In this research we have simulated two models of tall building with different side ratio and we have surveyed wind and earthquake loads in the different loading conditions. The models have been analysis in both time... 

    , M.Sc. Thesis Sharif University of Technology Miredris, Sohrab (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    To verify most of the numerical and analytical developments in the structural and earthquake engineering techniques, experimental methods have been considered by many researchers. For instance, numerical simulations in structural health monitoring, structural control and energy dissipation systems need to be verified and compared with experimental results. Consequently, research organizations spend substantial budgets on assessing and updating these experimental methods. Many of these experimental tests are essentially conducted on the benchmark structures with specific technical characteristics; these properties should not be changed after each experiment. Therefore, the tests on these... 

    Determination of Occupant Comfortability in Ttall Buildings with Outrigger and Aerodynamic Characteristics

    , M.Sc. Thesis Sharif University of Technology Hajiloo, Amin (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    In recent years, in Iran, like other countries tall buildings have been constructed as a solution to space limitation problem and modern architectural matters. By increase in building height,the flexibility against wind force increase, therefore necessitating the study of buildings behavior against wind force. Traditionally most of the research done, have dealt with performance of the buildings, probability of the failure, and the serviceability level all of which relates to the amount of force in elements, the stress existing in the structure, and the amount of displacement. A substantial factor in structures, especially in tall buildings, is the comfortability of their occupants which... 

    Seismic Vulnerability Assessment of Masonry Walls by Signal Processing

    , M.Sc. Thesis Sharif University of Technology Shahravesh, Masoud (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    In this study, damage detection of brick masonry walls using a unique signal processing technique has been addressed. Firstly, the pushover analysis and the calibration of the model is performed. Then, the dynamic analysis of the wall under earthquake excitation in three cases with different aspect ratios is conducted. Finally the dynamic properties of the system, namely natural frequency and modal damping ratio, are identified using continuous wavelet transform. The advantage of wavelet transform is its fine time-frequency resolution. The Morlet mother wavelet is used since it can provide the best time-frequency resolution based on Heisenberg uncertainty principle. Afterwards, the... 

    Passive and Semi-active Control of Adjacent Buildings Using Friction dampers

    , M.Sc. Thesis Sharif University of Technology Ashoori, Morteza (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    In this thesis will investigate control performance of coupled buildings. Control of this structures will done using friction dampers based on passive and semi-active strategies.
    A numerical study is employed to simulate a coupled building equipped with passive friction damper by using OpenSees software framework.
    Semi-active friction damper is used on three groups of adjacent buildings. At first, a mathematical model of coupled buildings is established for each group. The variable friction dampers consist of an actuator, which is based on a piezoelectric stack that alters the normal force at the contact area. A clipping control algorithm considered in the numerical study for the... 

    Seismic Performance Evaluation of Electric Power Equipment and Application of Base-Isolation for Electric Power Transformers to Improve Their Behavior and Reduce the Vibration Caused by the Earthquake

    , M.Sc. Thesis Sharif University of Technology Mojarad Dorbadam, Mohammad (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    This thesis is concerned with the performance of heavy equipments like electric substation transformers and bushings under earthquake loading. It begins with the description of the transformers, attached bushings, and some typical examples of substation failures in earthquake loading. This is followed by the field test and development of numerical models of transformer and two different types of seismic isolations, Natural rubber bearings (NRB) and high damping rubber bearings (HDRB) and in order to find the appropriate isolator, responses of fixed base and isolated transformers are compared. Important observations were made on the seismic responses of the transformer and its bushing.... 

    Seismic Evaluation and Rehabilitation of Historic Buildings: A Case Study about Soltaniyeh Dome

    , M.Sc. Thesis Sharif University of Technology Ghaemi, Mohammad Kazem (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Health monitoring of historic structures because of their cultural and economic importance is of great interest; also modeling and investigating the behavior of these structures is needed in rehabilitation procedures. Soltaniye Dome is one of the important masterpieces of Persian-Islamic historic architecture which is constructed during 14th century (1302-1312 AD). The Soltaniye building has an octagonal framework and a great dome. The dome has a diameter of 25 meters and total height of structure is about 54 meters.In this study, the macro modeling of Soltaniye building is performed using finite element software. In order to verify the modeled structure, ambient vibration tests are... 

    Evaluation of Seismic Criteria and Random Parameters on Fragility Curves of RC Frames

    , Ph.D. Dissertation Sharif University of Technology Asadi, Payam (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    There are many parameters which are utilized to obtain a more reasonable performance for structures under earthquake excitations in seismic provisions. It is well recognized that the main character to design of structures under seismic excitation is probabilistic rather than deterministic; therefore, it should be determined if the probability of structural damages is decreased when such parameters change in design of structures. In this thesis, fragility curves are developed in order to evaluate these parameters. Fragility curves are employed for various probability parameters. These diagrams are utilized to demonstrate when a coefficient or a number of parameters are used to improve... 

    Developing Seismic Fragility Curves for Seismically Isolated Bridges

    , M.Sc. Thesis Sharif University of Technology Bagheri, Hamed (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Purpose of this research is to investigate the effects of different seismic isolation techniques and effect of their location on seismic behavior of assymetric bridges and on mitigating their seismic demand. According to different types of isolators and their possible locations, a research is necessary to help to choose the optimum choice among different possible choices for isolators and their location. In this strudy, Lead-Rubber Beraing (LRB), Friction Pendulum Systme (FPS) and High Damping Rubber (HDR) isolators have been investigated and 3D bridge models are 3-span concrete box girder with 50 meters long each span and each interior piers, 7 or 14 meters long. Isolators also can be... 

    Developing Fragility Curves for Seismic Isolated Reinforced Concrete Structures

    , M.Sc. Thesis Sharif University of Technology Mostafavi, Ahmad (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    Nowadays, base isolation technique is widely used in the old and new structures, so it is necessary to assess the seismic performance of base-isolated buildings probabilistically, it is also essential to assess their performance during near-source versus far-field earthquakes.
    Developing the fragility curves is useful probabilistic method for the seismic assessment of structures. These curves define the probability of exceedance of different damage states for a given level of seismic intensity parameter. Former investigations has been done to assess the seismic behavior of base isolation systems consider base isolated highway bridge piers.
    In this thesis fragility curves are derived... 

    Probabilistic Evaluation of Ridge Isolation as an Inventive Method for Mitigating the Displacement of Isolated Buildings under all Possible Hazards

    , M.Sc. Thesis Sharif University of Technology Tavassoli, Sina (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    The main purpose of this research is to evaluate the probabilistic benefit of the implementation of second isolation layer in isolated structures to both the structure and the constructor. The innovation of this research is in the utilization of a seemingly useless part of the structure, which is the ridge, for mitigating the structure’s displacement. For this purpose, a five-story residential structure and its ridge have been isolated and modeled as an MDOF system with two degree of freedom in MATLAB software and the benefits due to the reduction in displacement and acceleration has been calculated. The results indicate 40 percent reduction in the main structure’s displacement and a benefit... 

    Evaluation of Seismic Response of Nonstructural Elements Utilized to New Isolation Technique

    , M.Sc. Thesis Sharif University of Technology Fahimzad, Ali (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    The purpose of this research is to investigate the seismic isolation method as a new method in seismic retrofitting of moving shelves. The shelves are used as a type of non-structural elements that are widely used, such as the maintenance of hazardous materials, telecommunication and computer equipment, preserving of pharmaceutical materials and first aid, displaying exquisite historical-artistic works, Storing goods in warehouses, and so on. In the new proposed method, the seismic isolation technology at the level above the caster for each of the four casters is separately used for seismic rehabilitation. In this case, there will be no disturbance in the normal use of the shelf. By studying... 

    Evaluation of Seismic Performance of Composite Moment Frame with Steel-Concrete Composite Column and Steel Beam Utilizing Fragility Curves

    , M.Sc. Thesis Sharif University of Technology Salehi, Mohsen (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    The purpose of this research is to investigate the seismic behavior of plane moment resisting frame consisting of steel-concrete columns and steel I beams utilizing fragility curves. Due to the great influence of the column type in seismic performance of structure. To reach an optimal system, different types of steel-concrete composite columns has been used in the models and the fragility curve of each one is compared. Steel-Concrete composite columns can be divided into three types: (1) concrete filled steel tube (CFT), (2) steel reinforced concrete (SRC) and (3) new combinations of (1) and (2). Due to the abundance of the use of concrete filled steel tube (CFT) and steel reinforced... 

    Development of Fragility Curves for Middle-rise Steel Structures with Additional Viscous Dampers

    , Ph.D. Dissertation Sharif University of Technology Rahimiasl, Mehdi (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    The objective of this research is to introduce a new comparative performance measure based on seismic fragility curve of structures. This measure is used here to investigate the efficiency of viscous dampers on the behavior of a weak mid-rise steel structure. Viscous dampers are commonly utilized to reach purposes such as decreasing the risk of the structure failure and restoration costs, weight reduction, and seismic rehabilitation of existing structures. These systems cannot be satisfactorily investigated using static loading concepts, and in order to achieve optimum design, conducting a nonlinear dynamic analysis is usually the most reliable procedure. Therefore, 5-span 12,15 and 18 story... 

    Development of Fragility Curves for a Number of Existing Buildings in Qazvin

    , M.Sc. Thesis Sharif University of Technology Soltanieh, Hamideh (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    The objective of this study is to assess seismic vulnerability and more specifically to develop analytical fragility curves for a number of existing buildings in Qazvin. Fragility curves represent exceedance probability of the structural response from a specific limit state at a given seismic intensity level. In this study, Maximum Interstory Drift Ratio and Spectral Acceleration at fundamental period of the structure with 5% viscous damping are considered as Damage Index and Intensity Measure, respectively. Limit states are also applied as it is suggested in FEMA 356. In order to obtain comprehensive and extensible results as far as possible, the type of buildings under study must be...