Sharif Digital Repository

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... 

This thesis contains experimental studies on mechanical properties of adobe and mud material and investigating seismic performance of a conventional adobe house using shake table tests. Mechanical properties of adobe and mud material were studied experimentally based on ASTM and BS standard tests. These experiments were designed to evaluate compressive strength of adobe sun-dried blocks and mud mortar cubes. Besides, shear behavior and tensile bond strength of adobe assemblages were under consideration and shear tests were done on adobe panels. As next part of the research, several shaking table tests were conducted on a dome-roof adobe house as a conventional representative of arch-roof... 

For the sake of decrease in energy and force of earthquake, seismic isolators are used. Regular seismic isolators are too heavy and damaged by chemical materials, therefore in this research a new approach is used that steel shim plates replaced by carbon and polyamide fibers. The aim of this research is to obtain the dynamic and mechanical properties of carbon and polyamide fiber reinforced isolators in comparison with steel reinforced isolators. In this approach, firstly some specimens have been designed and manufactured, then compresional and cyclic shear tests were carried out on them. All three type isolators are cylindrical and have identical diameter and height. The steel, carbon fiber... 

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... 

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... 

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... 

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... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a considerable percentage of houses are in the form of traditional buildings, and major losses due to recent earthquakes are because of masonry building collapse. In the early twentieth century in Iran every ten years a destructive earthquake has been occurred which has resulted in huge human casualties and economic losses. After the Bam 2003 earthquake, a team project was defined to investigate the behavior of rural houses with the aim of providing solutions to lessen seismic hazards, and the current study is the fifth phase of the following line of investigations. Among the existing kinds of rural... 

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... 

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... 

After the heart-rending earthquake in Bam and its severe losses, the engineering community forced to pay special attention to the seismic vulnerability of traditional structures. Therefore, with the aim of reducing of such devastations to minimum, a multi-phase research project was defined at Sharif University of Technology to study the vulnerability and retrofitting of these structures which the current study is the eighth phase of that series research. In the third and fourth phases of this project, a typical adobe building with dome roof was chosen for study making use of shaking table facilities. The tests included both un-retrofitted and retrofitted states and considerable seismic... 

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... 

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... 

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... 

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.... 

Adobe structures are considered as masonry structures which are out of scope of 2800 Iranian code. Due to this code, since these structures are made of weak materials, they do not have a considerable resistance to earthquakes. Since these structures can be found all around Iran; therefore, seismic study of walls as an important component of these structures, is, indeed, necessary. During this study, cyclic tests on three types of adobe walls, without opening, with window-opening, and with door-and-window-opening with a scale of 2:3 were done to study their in-plane behavior and also their failure modes. Based on our observations, in these walls, because of small ratio of height to length,... 

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... 

Adobe structures are considered as masonry structures which are out of scope of 2800 Iranian code. Due to this code, since these structures are made of weak materials, they do not have a considerable resistance to earthquakes. Since these structures can be found all around Iran; therefore, seismic study of walls as an important component of these structures, is, indeed, necessary. During this study, cyclic tests on three types of adobe walls, without opening, with window-opening, and with door-and-window-opening with a scale of 2:3 were done to study their in-plane behavior and also their failure modes. Based on our observations, in these walls, because of small ratio of height to length,... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

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...