Sharif Digital Repository

The main need in material related design is the true knowledge about the material properties. Existence of the cracks in the structure of materials is one of the main sources of weakness in the materials. Experimental evidences confirm that the surfaces of the cracks are mainly irregular, but in the existing theories in fracture mechanics all of the results are derived through the assumption of mathematical crack with smooth surfaces or at best with simple geometrical shape. In recent years, after it is being confirmed by experimental results that the fracture surfaces are fractals, several researchers tried to investigate the effect of the roughness of the fracture surfaces in the relations... 

One of the passive control systems that are used widely in today’s buildings are metallic yielding dampers. Metallic yielding dampers by absorbing earthquake input energy, prevent inelastic defromations form in beams and columns. In this research, the behavior of an innovated metallic yielding damper, named pistonic damper is investigated. This damper consists of a number of circular parallel plates with constant or variable thickness that dissipate seismic input energy by flexure yielding in small displacements. at large displacements stress field in plates is changed and this caused the stiffness and strength of damper are increased and show shell behavior. this kind of behavior... 

The purpose of this study is to investigate the seismic performance factors of a structure with the composite shear wall system that, if properly implemented, a nonlinear seismic design process will lead to safety against earthquake collapse. In this research, a special type of composite shear wall is investigated, which consists of a steel plate in the middle of the reinforced concrete shear wall. The purpose of this combination is to improve the performance of the wall because steel plates can effectively improve the seismic behavior of the structure, and concrete can protect the steel plate from buckling and corrosion. In this study, numerical models are validated according to previous... 

The reinforced concrete deep beam is a structural member with mostly shear behavior that can be seen in various members such as beams of bridges and tall structures, girder beams, and equipment-carrying beams in industrial structures. Due to the non-linearity of the strain in these members, various parameters are important in their behavior and response, including the compressive strength of concrete, the type of loading, the type and amount of shear reinforcement, and the cross-sectional dimensions. Deep beams' ultimate damage and failure are generally shear, brittle, and sudden. Therefore, considering the importance and sensitivity of these crucial structural members, it is necessary to... 

Coupling beams have had a widespread application as performance enhancing devices within concrete structures and more recently, also in steel structures. However, the conventional coupling beams are not so efficient in coupling distant walls. In this paper, a novel form of coupling members, namely, Coupling Panels is proposed and then, the application for a nine-storey building is investigated. Coupling panels are steel plate shear walls which are exerted in the intermediate spans between adjacent shear walls, and act as a mega coupling beam. First, a verified finite element model is constructed to demonstrate coupling panel behavior along with its global structural mechanism. Subsequently,... 

This thesis aims to study the dynamic behavior of circular and annular plates. First, free vibration of the plate, resting on a Pasternak foundation with a variable subgrade modulus, by using the infinite power series method is presented. The proposed method applies to various boundary conditions with no restriction. A comprehensive study is carried out to investigate the effects of the different parameters on the behavior of the plate. The obtained results demonstrate that the Pasternak foundation has a significant influence on the natural frequencies and greatly increases them. Secondly, the dynamic response of thin and moderately thick plates subjected to a moving load is considered. In... 

The primary objective of this fundamental research is to examine the nonlinear spherically symmetric wave propagation and the dynamic response of a sphere with an inclusion region having symmetrically distributed eigenstrain. The sphere is assumed to be composed of a specific compressible nonlinear elastic material whose behavior is described by the practical Blatz-Ko model. To achieve this, the study is divided into two main parts. In the first part, the governing dynamic equilibrium equations are derived using established methods in nonlinear elasticity theory. This approach begins by transforming the initial configuration into a manifold with Riemannian geometry, referred to as the... 

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... 

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... 

This paper investigates the behavior of the Y-shaped bracing system. Because of the special type of eccentricity in this system, the behavior of the frame is strongly dependent on the geometrical changes of the braces. So that even in the elastic region, it shows the geometrically nonlinear behavior. The amount of eccentricity is very effective on the nonlinear behavior of the frame. Also the ratio of cross sections of the bracing members has a very important impact on the expected performance of the frame. The results show that this system tolerates large displacements, and can act like a base isolation system. Firstly, using a two-dimensional accurate modeling related to the geometrical... 

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... 

The Response modification factor R represents the behavior of the structure such as ductility, overstrength and the inherent redundancy. This factor shall be defined according to the type of lateral force resisting system. However, there are some complexities and/or uncertainties in codes related to the R factor according to the height, form of irregularities and structural systems. Therefore, from the scientific point of view as well as reliability, it is very clear that the R factor cannot be similar for all kinds of structures, categorized as a specific group. In this investigation, assuming a low-rise, vertically irregular structure with a heliport which has a dual structural system... 

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... 

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