Sharif Digital Repository

Dynamic response of structures, against ground motion, is one of the most important issues in earthquake engineering. A variety of approaches and apparatus have been developed for this purpose. One of these equipments is metallic dampers. Such apparatuses provide damping, accompanied with reasonably strong lateral stiffness; hence, they are named as “Added Damping And Stiffness” (ADAS). The present study aims to evaluate the performance of a common metal damper consisted of triangular metal plates known as “Triangular Added Damping And Stiffness” (TADAS). In this investigation, the performance of TADAS, in an eight story irregular in plan steel structure, is extensively considered. A 3-D... 

In this thesis, the behavior of proposed moment resisting precast beam-column concrete connection under cyclic and monotonic loads is investigated. In this study, the finite element models of precast and monolithic middle and corner connections are created. The results of finite element analysis under cyclic loading is verified with existing experimental results based on failure mode, ductility, energy dissipation capacity and flexural strength. Based on the results of nonlinear finite element analysis, the analytical behavior of samples is in good agreement with experimental results and finite element analysis of proposed precast connection can be replaced with supplementary tests. Then the... 

With occurring severe earthquakes, damages of columns in RC buildings can lead to overall failure and collapse. So retrofitting of such columns that do not comply with the design requirements is necessary to prevent such phenomena. A variety of methods has been introduced so far for retrofitting. The key factors in determining the retrofitting methods are being economic and easily implemented in the design. Confining concrete columns with pre-stressed steel strips is a new technique that is simple and economic. Previous experimental experiments have shown that this method can enhance ductility and overall seismic behavior of such columns.
In the present study three and six story frames... 

Composite systems consisting of concrete columns and steel beams are introduces as structural systems in recent years. These structural systems enjoy merits of both steel and concrete frames by efficiently combining the advantages of them. This study is allocated to lateral force resistance system using armed concrete and structural steel. Advantages of composite structures rather to those of two other conventional ones are among performance characteristics under ultimate loads, economical conservation, and higher speed of construction.In this research the aim is to study these frame under earthquake induced loads. The seismic performances of these composite frames with through column beams,... 

Tunnel form structures have been proposed in building industry during 40 years for financial saving, suitable structural performance and seismic behavior, and the possibility of performance in an industrial form; and they have also been brought up as one of the innovative technologies of construction in Iran for a couple of years. So far, these structures have been subject to study by the researchers less than frame structures. In comparison to the common structures, evaluating the behavior of these structures is analyzable as two or three-dimensional elements. In this research, the nonlinear behavior of these structures has been simulated and evaluated by using three-dimensional elements;... 

Explosion as a physical phenomenon have various effects on the environment, including living organisms, surrounding buildings, equipment and infrastructure there. Due to such extreme loading conditions, efforts have been made during the past three decades to develop methods of structural analysis and design to resist blast loads. The analysis and design of structures subjected to blast loads require a detailed understanding of blast phenomena and the dynamic response of various structural elements. The most appropriate method for evaluating the behavior of structures under blast loading is performance approach which specifies the response of structures against explosion. It seems that... 

Today, with the replacement of the old method of force-based design by the new method of performance-based design in structural and earthquake engineering, many structural and earthquake researchers have focused in their studies on this area. The performance-based design aims at enabling engineers to design structures with predictable performance. Designing space structures has particular complexities. In space structures, the failure of a structural member does not necessarily mean the failure of the entire structure, because the redistribution of power will occur between the adjacent members after the failure of a member and the structure can thus have further support capacity. Similarly,... 

Considering connections as ideally rigid or pinned is a common assumption during design and analysis of steel moment frames. However, in real world, steel connections show a non-linear behavior between these two ideal states. The aim of this research is to investigate the effect of partially restrained connections on the design and performance of two-dimensional steel moment frames under vertical and horizontal loads that are applied statically. For this aim, nonlinear finite element modeling is used in probabilistic evaluation process to assess the performance of existing structures. To capture the real behavior of structure in models, geometric and material sources of nonlinearity are... 

Problems with composite materials can indicate the lack of mechanical properties of the layers, especially in high temperature, which led to the expansion of functionally graded materials. The most important application of these materials is in high temperature environments .therefore the study of their behavior under mechanical and thermal loads in the range of small and large deformations is very important.The purpose of this research is to provide an analytical solution for nonlinear behavior of functionally graded circular sector plates under thermomechanical load.The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction... 

In this research a new type of external post-tensioned concrete slab is proposed. In this system, the tension force of cables is used as upward force acting at the bottom face of slab. To achieve this behavior, two short concrete columns mounted at the bottom face of slab and act as the middle supports for the cables. Based on the cable force and its angle, an upward force is applied to the slab at the location of columns. In fact, a truss structure comprising of the concrete slab as compression cords, cables as tension cords, and columns as ties. By virtue of Kirchhoff’s plate theory, an analytical treatment of the slab under gravity loads is addressed. For analytical study, it is assumed... 

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 numerical modeling of engineering contact problems is one of the most difficult and demanding tasks in computational mechanics. Frictional contact can be observed in many problems; such as: crack propagation, metal forming operation, drilling pile etc. The thermodynamic coupling problems arise naturally in many industrial processes, such as thermal protection structures ,nuclear fuel elements, layerd structures , heat exchanger as well as metal forming. In these situations predicting temperature field as well as the stress field is of considerable applied importance. When two or more bodies are forced to contact whit each other as a result of thermal or/and mechanical load thermodynamic... 

By constraining the steel members against lateral buckling, buckling-restrained braces (BRB’s) show similar load-deformation behaviors and energy absorption capacities in both tension and compression. As a result, BRB’s demonstrate significant energy dissipation capacity compared to ordinary braces. On the other hand, the relatively small post-yield stiffness of BRB’s usually leads to significant residual drifts, which may render the structure unusable. In recent decades, significant research has been put into improving the performance of structures equipped with BRB’s. In this project, the current methods to enhance the performance of the BRB’s are explored, and novel approaches are... 

Study of dams' behavior and their safety against earthquakes has been interesting due to the high rate of failure. In the past, this study was just about linear analysis of dams. However, the weakness of concrete in tensile strength results in cracks in body of dams. Therefore, the nonlinear analysis of these huge structures seems to be so important. Many researches have been done in this field to model dam-reservoir-foundation with effects of concrete nonlinearity. In spite of the fact that gravity dams' safety depends on cracking status and consequently on nonlinear behavior of concrete, we cannot reach accurate and suitable results for dynamic behavior of concrete dams because these... 

In this study, linear and nonlinear mechanical behavior of moderately thick annular sector plates made of functionally graded materials is investigated. In linear analysis, based on first order shear deformation theory, governing equation with two different approaches are derived. In first approach, by application of extended Kantorovich method (EKM), displacements field variables are expressed as separable function of and together, and two sets of ordinary differential equations (ODEs) by using the principle of minimum total potential energy are derived. In the second approach, within FSDT and using the principle of minimum total potential energy, the governing partial differential... 

Despite all the developments of construction industry, there are some limitations in this important industry. For example, one of the common limitations of buildings is restrictions of architectural designs that often rise due to location of lateral load-resisting systems of buildings and usually rise disagreement between structure and architecture engineers. The lateral load-resisting systems and location of them are very important, therefore, in this study we attempt to investigate the changes of their location in structure’s stories. Due to architectural restrictions, the removal and movement of lateral load-resisting systems have been done only in some stories or from a story to the... 

The purpose of this research is to provide an analytical solution using first order shear deformation theory for nonlinear bending of rectangular FG plate under mechanical and thermal loads with different boundary conditions. To achieve this goal, extended Kantorovich method have been used. This method has a high convergence rate and is more accurate than other approximate methods, such as the Ritz and Galerkin methods, because the partially differential equations are converted to ordinary differential equations. In order to solving nonlinear odes the perturbation method is used. Material of the plate is a mixture of ceramic and metal and is modeled as an isotropic and non-homogeneous... 

Functional Magnetic Resonance Imaging (fMRI) is a recently developed neuroimaging technique with capacity to map neural activity with high spatial precision. To locate active brain areas, the method utilizes local blood oxygenation changes which are reflected as small intensity changes in a special type of MR images. The ability to non-invasively map brain functions provides new opportunities to unravel the mysteries and advance the understanding of the human brain, as well as to perform pre-surgical examinations in order to optimize surgical interventions. To obtain these goals the analysis of fMRI is the first condition which should be met. First methods were linear and assumed the...