Sharif Digital Repository

It is well known that the most rigorous method to assess the performance and to predict the seismic demands of a structure subjected to earthquake is nonlinear time history analysis. However, this technique is accompanied by complexities and difficulties in evaluating the seismic demands of structures and requires superior knowledge and skill. As a result, in recent years, nonlinear static analysis has been proposed in performance based design procedures. One of the primary assumptions of nonlinear static procedures is that the behavior of a structure with multiple degrees of freedom (MDOF) subjected to seismic ground motion can be estimated from the response of an oscillator with a single... 

The primary goal of seismic design requirements of building codes is to protect life safety of occupants during severe earthquakes. Thus it is required that collapse probability of designed buildings to be acceptably low. However current design codes are strength based and intrinsically experimental. Thus collapse safety of buildings designed by these codes is not known quantitatively. The history of formation and update of seismic building codes is marked by big earthquakes; often serving as landmarks for the evolution of seismic codes and detecting its deficiencies. As time passes, the design criteria become more and more articulate and ambitious, just as the design objectives evolve from... 

In this thesis, the semi-hinged connections such as double-angle connections, which are welded to the beam web and bolted to the column flange, are investigated. In this study it's tried to establish the effect of clearance setback between beam end and column flange and/or web. When the beam rotates, it is desirable to avoid the bottom flange of the beam bearing against the column as this can induce large forces in the connection. The usual way of achieving this is to ensure that the connection extends at least a few millimeters beyond the end of the beam. For this purpose, several connections are designed and considered, based on two different shear capacities for the beam. For each... 

Dynamic behavior of space structures are of great complexities. On the event of severe earthquake these structures exhibit high resistance and on the other hand, their high rigidity and small deformation makes it necessary to pay attention to their dynamic behavior, especially when combined with other types of structural systems. Also due to lack of sufficient codes and references, their dynamic behavior is still unknown to a great extend. Among these kinds of structures, reinforced concrete double curvature shells, and especially funicular shells, are much more important than others. In this thesis, dynamic response of these kind of structures, especially reinforced concrete domes, in... 

General tall buildings consist of different types of structural systems, such as moment resisting frames, with and without shear walls, braces and outriggers. These types of structure have been widely analyzed by many researchers. However, only a few publications are available on the comparison of these structural systems with different stories. In this investigation five types of common structural systems including special moment resisting frame(SMRF), pin structure plus brace, pin structure plus shear wall, SMRF plus brace and SMRF plus shear wall are studied and by doing linear dynamic analysis, a criterion for both lateral displacement and steel tonnage of structures was presented.... 

Steel bracing systems can be used effectively for seismic retrofitting of existing RC buildings as well as for seismic design of new building. Steel bracing system has been used to increase the lateral load resistance of steel structures. In recent years the concept of steel bracing has also been applied to the retrofitting of reinforced concrete frames, especially to improve seismic performance of non-ductile reinforced concrete buildings. The use of steel bracing systems for seismic rehabilitation of RC frames offers some advantages such as (a) minimal added weight to the structure; (b) ease and speed of construction;(c) increased architectural flexibility; in comparison with RC shear... 

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 research, a structural lateral bracing system called ‘Chevron Knee Bracing’ (CKB) on reinforced frames is investigated. This new form of framing system is constructed through the knee and the diagonal brace elements. The diagonal brace component provides the required level of lateral stiffness and stays in the elastic range without buckling at any time. However, the knee part is a fuse-like component that dissipates energy by the formation of plastic flexural and/or shear hinges at its ends and mid-span, when the building is subjected to severe lateral loads. For this purpose, first, by elastic studying of the system, three new and practical parameters are established. Then, the best... 

Base plate is one of the important and sensitive elements of a structure which roles as a connector of force and moment in column to foundation joint and prevents from stress concentration in the joint area. As until now there has been several numerical and experimental researches conducted about base plate connections, but in practice for design, base plate is considered as a cantilever beam which undertakes compressive force and bending moment. In this method of design many important factors such as separation and deflection of base plate, interaction of base plate with bolts and foundation aren’t taken into consideration. Therefore there is an urgent need to design base plates considering... 

The Overstrength, Ductility and the Response Modification Factor (R) for 70 steel X-braced , Inverted-V-Braced and Offcenter Bracing System frames were evaluated by performing pushover analysis of model structure with various stories (3,6,9,12&15 story) and span length (4,6&8 meter). Some result were compared with those from nonlinear dynamic analysis. According to the analysis result the R factors obtained from nonlinear dynamic analysis are 15% more than obtained from pushover analysis and R factors computed from pushover analysis were generally smaller than the values given in the design codes. R factors in Irregular structure in height are about 90% of R values in regular structure in... 

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... 

On the ground, it is necessary to have the values of Response Modification Factor R, Over-strength Factor Ω0, and Deflection Amplification Factor Cd to design seismic-force-resisting systems according to design and loading codes. This study is intended to evaluate these factors for a structural lateral bracing system called Chevron Knee Bracing (CKB). In this type of bracing, the knee elements help the system to dissipate energy through the formation of plastic flexural and/or shear hinges within the presented bracing system. The ap- proach used in this study is according to FEMA P695 based on low probabili- ty of structural collapse and involves nonlinear static and dynamic analyses.... 

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,...