Sharif Digital Repository

In the past few decades, shaking tables are widely used to evaluate system response of structures under seismic excitations. These devices are used without any fundamental research performed on a shaking table system as an entity model. In most of these studies for simplicity, it is assumed that there exist no considerable vibration and displacement around the shaking tables, and no attention is paid to the peripheral substances such as soil settled under the foundation.
In this thesis, result of ambient vibration test on shaking table system (solid deck, concrete foundation and soil layer) has been presented. Precise sensors known as low frequency and high accuracy accelerometers have... 

Investigation of the dynamic characteristics of an existing structure system based on field tests is of practical significance, since it can be employed in the field of examining construction quality, validating or improving analytical finite element structural models, or conducting damage assessment. The main purpose of this study is to investigate the dynamic characteristics of dams using the seismic response data. Whereas, in the process of frequency domain identification of dam properties, frequency response function (FRF) plays the most important role, evaluating the corresponding parameters with better accuracy has always been desirable. Therefore, a comparison was made between some... 

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... 

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... 

Sensitive equipment, are vulnerable to strong earthquakes, and failure of these equipment may result in a heavy economic loss. Recent studies have revealed that a conventional passive seismic isolation system may induce an excessive displacement when it is subjected to a near-fault earthquake that possesses strong longperiod components.
Semi-active control devices are capable of offering the adaptability of active devices and stability and reliability of passive devices that have been considered by many researchers.
Magnetorheological (MR) damper is a reliable semi-active control device which works in a wide range of temperature besides its mechanical simplicity at a modest... 

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... 

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... 

Due to structural and nonstructural damage after the occurrence of Northridge 1994 and Kobe 1995 earthquakes, Seismic design basics was modified and philosophy of performance based design was suggested. In this novel solution, Predefined limitations are considered. Performance criteria were usually related to displacement or other correlated factors such as hinge plastic rotation. All the mentioned limitations are related to different damage states.Most of the codes and articles use following assumptions for assessing structural performance: 1) considering first vibrational mode for structural response to any seismic excitation regardless of seismic input acceleration records or structural... 

This study focuses on the risk assessment of reinforced concrete tall buildings subjected to ground motion excitation. In order to assess the vulnerability of tall buildings, twelve-, and twenty-four-story four-bay reinforced concrete moment resisting frames are studied. This evaluation is done through developing fragility curves. These fragility curves provide the probability of exceeding the multiple damage states for a given intensity (e.g. CAV) of ground motion excitation. To develop the fragility curves, a great number of nonlinear dynamic analyses were conducted in the open-source platform OpenSees. Since the PEER Guidelines for Performance-Based Seismic Design of tall buildings (PEER,... 

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... 

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... 

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... 

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... 

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... 

Bridges are one of the most important parts of the transportation network and play an important role in relief after earthquakes. Therefore, detecting where and how much damage take place is vital. Bridge structure is consist of two parts: substructure and superstructure. Usually, superstructure remains intact during earthquake because of rigidity and high strength of it. In the other hand, damage localizes to substructure. We also use high safety factor to piles and cap piles so they experience little or no damage. As a result, columns suffer damage more than other parts. In this study, the focus is on columns damage. This study also is limited to non-prestressed multi-cell box girder... 

Performance – based design is a new concept that has been developed in recent years. Given that roof displacement and story drifts determine the performance of the structure during an earthquake, displacement – based design has been considered to be an effective method for performance – based design. However, limiting the maximum displacement would not necessarily lead to a desirable performance; especially in long – duration earthquakes. Thus consecutive loading cycles and the effect of hysteretic energy should be taken into account. Combining displacement – based design with energy principles will lead to a suitable design method. This study presents performance – based plastic design... 

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...