Sharif Digital Repository

Theory says that prudential fiscal policies can mitigate the unintended consequences of business cycles. Does evidence support the effectiveness of fiscal policies is still a challenging question. In this thesis, I focus on the relationship between fiscal policies and aggregate movements in oil producing countries. I found significant pro-cyclicality in these countries in which questions the goal of their policy making. Furthermore, I show that in my sample of oil producers,data doesn’t support the poorer is the country, the higher is the pro-cyclicality of their fiscal policies  

The Reliability of substation structures with consideration of earthquake uncertainties is one of the most important subjects in structural analysis in recent years. In this project we first introduce IEEE-693-2005, which is the most effective and comprehensive seismic design code for electronic substations. Also in second chapter the rudimentary aspects of Reliability Theory and methods for evaluating the reliability of substation structures is introduced. Then with modeling the most common and most important electronic substation devices in Iran, with consideration of all seismic parameters and their uncertainties, the reliability of these structures evaluated. In this project for... 

In this thesis behavior of intermediate steel moment frames and intermediate steel moment frames equipped with knee element are investigated. The knee element attaches to the beam element by inverted-V type concentric braces. The knee element acts as a fuse to dissipate input energy during an earthquake by the formation of plastic hinges. On the other hand, brace elements remain in the elastic range without buckling and provide suitable lateral stiffness. Main object of this investigation is reducing deteriorations in the main frame in intermediate and sever earthquake by concentrating deteriorations in knee element. Whereas knee element is not a main element of the frame, retrofitting of the... 

A particular kind of concentric bracing system composed of three members arranged in y-shaped geometry is examined in this thesis. The non-straight diagonal strut of this off-centre bracing causes eccentricity to the system and is connected to the frame corner through a third member. Providing adequate openings in braced bays accompanied by improved energy dissipation are resulted in positive attitude toward using y-bracing frame as a lateral load resisting system. However, lacking of specific design codes could be problematic for engineers. To overcome this incompetency, seismic performance factors including the response modification coefficient, the system overstrength factor, and... 

Developing new micro and nano devices, help us instruction micro and nano devices in very small scales. Also nano technology improved in recent decades especially in century 21th. These devices contained many important members, such as micro and nano filters, micro channels, sensors, and electrical chipsets. Navier-Stockes equations with slip and no-slip conditions can not used in transition and free molecular regimes. Since most of the MEMS and NEMS devices working in slip and transition regimes, then we must using DSMC for simulation these devices. DSMC is a physically method and working on the physics bases. Also it was derived from Boltzmann equations by Bird. In this study, we want... 

Use of micro/nanoelectromechanical systems has become increasingly prevalent in recent years. Therefore, the development of technologies and understanding of fundamental physics associated with them is necessary.In micro-and nano-scale different behavior is often observed and it is due to Knudsen number that forms different types of flow regimes. When the flow is considered to be continuum; for it is in the slip-flow regime, for it is called the transition-flow regime. When , the flow is considered to be free molecular and is sufficiently rarefied to allow molecular collisions to be completely neglected in analysis. For continuum and slip flow regime the Navier-Stokes equations with... 

Steel plate shear walls are lateral load resisting systems, especially against earthquake excitation. They are constructed with or without stiffeners. Stiffened walls are more ductile than without stiffeners walls. In this research, nine thin steel plate shear walls models were considered in three groups of 5story, 01story and 05 story walls. In each group different yield point steel for the infill plate was used. The results showed that, using low yield point(LYP) steel will increase energy dissipation of models up to %36. LYP also improve shear capacity of models up to %96. The results showed that using LYP will cause lower lateral displacement in models  

This thesis presents the investigation and development of a Finite Element Model (FEM) for a new type of Beam-Column Semi-Rigid steel connection. One of the main parts of this connection is a steel T profile inserted on top of a beam connecting it to a column by bolts. It seems that changes in the geometry of the T profile and its bolt positions can have a great influence on the rigidity or flexibility of the connection. Therefore, meaningful categories of the T profile geometry with different bolt positions have been modeled and analyzed by means of a Finite Element Modeling software ABAQUS, and their moment-rotation curves were driven. Also the Initial and Nonlinear Stiffness and the... 

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 stiffeners 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 1,3,5,7 and 10-story regular and irregular building structures which have un-stiffened steel shear walls with 3, 4.5 and 6 millimeters thickness with... 

Today steel tubular systems are used more than before, especially in recent years. A difficulty with this type of systems is making beam to column connections using bolts due to no access to holes of bolts from the inside of tube or hollow circular column. Reverse channel connection is devised and introduced to prevail this problem. Access to holes in this connection is from the inside of channel. In this connection, the web of the channel is connected to steel beam using bolts and the two legs of channel is welded to face of tube column.
This type of connection does include some innovations; not too many researchers work on different versions of this connection. This thesis provides an... 

In this study dynamic response of Timoshenko beam and rectangular Kirchhoff plate under moving mass are investigated. Applying Hamilton’s principle, governing differential equations of beam and plate are derived considering the effect of moving mass. Afterward, a numerical-analytical solution based on eigen function expansion method for analyzing nonuniform beams and plates by means of beams’ and plates’ free vibration modes is presented and convergence of the solution is proved by proving that the governing differential equations of Timoshenko beam and Kirchhoff plates are self adjoint. Modal orthogonality circumstances are discussed due to their important role in eigen function expansion... 

In this thesis, in order to evaluate the vulnerability of concrete structures equipped with Yielding Element (YE) against earthquakes, two single story/ span concrete frames with different bay-to-height ratios (B/H<1 and B/H>1) are considered. Since the nature of earthquakes is to release energy due to tectonic movements in the earth and the nature of damages in structures depends on the rate of absorbed energy, investigating the behavior of structures are based on the energy concept which is considered as the most important way to design structures against earthquake load. In order to provide seismic resistance against earthquakes and reduce the damages in main elements, it is required to... 

This thesis illustrates the typical seismic retrofitting of bridges using a model governing transverse seismic response of retrofitted bridges by simplified analytical models of the end diaphragms based on the fundamental dynamic concept as well as previous research works. For three types of ductile diaphragm devices such as Eccentrically Braced Frames (EBF), Triangular-plate Added Damping and Stiffness Devices (TADAS) and Chevron Knee Bracing (CKB)and Shear Panel System(SPS), finite element nonlinear analytical models are developed in separate flexural and shear yielding modes, and the capability of the proposed finite element models is ascertained.The IDA (Incremental Dynamic Analyses) are... 

In the present study, a number of Steel Plate Shear wall (SPSW) models with various infill plates such as perforated and slit infill panels are analyzed and the results are utilized to discuss about behavior of Steel Plate Shear walls with various infill plates. The ABAQUS finite element package is utilized for all Eigen value and incremental nonlinear pushover analyses. Cyclic loading is in compliance with the ATC 24 loading protocol (ATC 1992). To validate modeling, boundary conditions and loading procedures, the experimental results provided by Darren Vian et al. [102, 103] and In-Rak et al. [48, 49] was modeled and analyzed. Investigation of steel plate shear walls made of different... 

PVDF (polyvinylidene fluoride) magnetic nanocomposite films were prepared by solution casting using two types of nanomagnetic particles: (i) magnetic nanoparticles synthesized by using an alkaline solution of mixed ferrous/ferric salts along with oleic acid as a coating agent at 70˚C; (ii) Fe3O4 nanoparticles prepared by hydrolysis of aqueous solution of ferrous/ferric salts with potassium hydroxide at room temprature. Scanning electron microscopy (SEM) showed that the PVDF magnetic nanocomposite had a porous structure with Fe3O4 nanoparticles dispersed inside the porous polymer matrix. The presence of crystalline magnetite within the polymer matrix was confirmed by X-Ray diffraction method... 

The main objective of this research is to provide an estimation of the amount of rent in Iran as an oil economy. First by reviewing recent studies, the concept of rent was extracted and the rent measuring indexes were assessed. Having considered the four categories of rent in Iran, budgetary rent, interest rent, import rent and energy rent, the amount of rent in Iran’s economy during (1369:1-1386:4) was estimated. Results show a considerable increase of rent during (1369:1-1372:4) & (1384:1-1386:4). In the next section of this study the long run and short run relationship between rent and some of the macro economic variables was estimated.In this section the co-movement of rent trend with... 

Concerning the variety of existing buildings and the diversity in the factors which affect the behaviors of structures, subjected to earthquakes, presenting a definite method for studying their seismic vulnerabilities has not been realized yet. Selecting a method which covers all mentioned necessities is extremely wide and complex. From one side, the capacity of structural system should be determined based on its strength and deformability. On the other hand, the nonlinear behavior of structure should be predicted by selecting the probable effects of earthquake on the region. Then, the force or acceleration which causes damage of structure's components, and the whole structural system,... 

In this thesis project the effect of joint rigidity on the behavior of steel braced frames has been investigated. In order to carry out this study on the efficiency of semi-rigid connections, a series of 3-bay braced frames ranging from 6- to 20-story with extended end-plate and flush end-plate connections have been selected and designed. This study has been extended by evaluating the role of the mentioned connections on seismic performance of selected semi-rigid frames under seven famous earthquake records. Having taken a particular performance level, in this case, “life safety” the target displacement and also the lateral load pattern for each frame have been calculated. Then using a... 

The flexibility of beam to column connections and its effect on behavior of steel structures is one of the most important problems, which is interesting to engineers and scientists for more than 80 years. Hence many studies conducted on this topic to clarify the behavior of this type of connection. In this work, it is tried to study the behavior of double plate connections, which are welded to the beam web by finite element modeling and mathematical method. A novelty of this thesis is some top trough plate which has been implemented to column under beam flange. Based on finding of this thesis few recommendation can be made related to usage of top trough plate. In brief reduction of... 

Macroeconomic stability, namely reduction in output fluctuations and inflation level and volatility, has been a major policy for policymakers. Therefore the way of choosing monetary policy to achieve the mentioned object has a great importance in macroeconomics literature. Currently, the best known monetary policy models are based on Taylor rule. These rules adjust interest rate with respect to inflation and output deviation from the target to minimize fluctuation in inflation and output. Formerly, McCallum rule was widely used, which adjust growth rate of the money base in response to nominal GDP deviation from the target to minimize nominal GDP fluctuation. To evaluate the performance of...