Sharif Digital Repository

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... 

The current design procedure known as Force-Based Design (FBD) method, generally, does not lead to uniform distribution of drift, hysteretic energy, and ductility demands (or structural damage) along the height of the moment frames under strong earthquakes and these performance parameters can be much higher and concentrate damage on one or more of the lower structural stories. This paper presents an iterative wave propagation (WP) based technique to calculate the seismic nonlinear response of multistory buildings as an extension of the layered soil media, founded on bedrock and subjected to vertically propagating shear waves, which leads to the introduction of a new Lateral Load Pattern... 

This study aims for investigating a novel type of Steel Plate Shear Wall (SPSW) system in which the plate to boundary column connections are eliminated and the plate is reinforced with side, horizontal or cross stiffeners. SPSWs are one of the best lateral load resisting systems specially in high-rise buildings which makes it to be widely used in modern construction projects. SPSW system was first used in Japan and United States and found its way to other countries through the next years. In contrary to United States, stiffened SPSWs are more popular in Japan as it is a high seismic area. Despite the numerous advantages of this system, the main drawback of SPSWs is the large column sections... 

Over the last years, terrorist attacks and accidental explosions have brought on a need for research in the field of structural engineering to study the response of a building subjected to blast loading conditions. An explosion within or surrounding a building, not only can have disastrous effects causing both structural damage or failure, but may also lead to the death of human beings.In order to prevent these catastrophes and gain a better understanding of responses of the buildings and lateral resisting systems with different characteristics, the study of the behavior of the lateral resisting systems under blast loading conditions is essential. This research will also aid in the... 

This research studies behavior and implementing of telescopic lead shear damper in structures. Telescopic lead shear damper (TLSD) is a type of metallic yielding dampers that can dissipated energy with usage of shear yielding of lead. TLSD is made from behind act of two lead shear damper (LSD) like a telescope. Lead shear damper composed of two coaxial steel pipes where their interfacial gap is filled with pure lead. The interface of lead and steel pipes are roughened in a threaded form to guarantee the no-slip condition across the interface. Due to stable and fat force displacement hysteresis loops of TLSD, this device can be used in structures subjected to wind, seismic, and other dynamic... 

Aiming to improve the extraction performance of wind energy has led to the noticeable increase of the structural dimensions in the modern wind turbines. The larger blade with more flexibility experiences large structural deformation even under nominal operational loading, so the nonlinear modeling and analysis of these structures have become as important subject of the recent wind turbine researches. In this dissertation, the geometrical exact model of the rotating wind turbine blade under the effects of the tower tip's motion, and also the operational loading comprising the aerodynamic and gravitational loadings is presented. In this way, the geometrical exact beam formulation is developed... 

Considering the interaction of flexural moment and shear force in the steel frames with haunch or intermediate beam length and eccentrically braced frames with intermediate link length is a major concern of the structural analysis and design. This paper contains two stages. In the first stage, to investigate the moment-shear interaction for the highly ductile steel I-sections, a study is carried out using finite element analysis and a simple and practical relationship is developed. In the second stage, a simple approach based on virtual work method for assemblage of interconnected rigid bodies, is employed to consider collapse mechanisms with mixed hinges. Using this approach, the... 

One of the most important problems that challenge the researchers in modeling physical phenomena is the Impact Problem. The complexity of impact problems is due to the fact that this problem consists of various sub-problems, each of which of high complexity and in order to have a clear understanding and correct modeling of the problem, one needs to address each and every one of these problems with great effort, severity and punctuality.Impact problems often involve one or more dynamic systems that can also be subjected to dynamic loading. This loading could be a result of external agents or dynamic interaction of the two bodies with each other. In cases where the problem involves interaction... 

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,... 

In this thesis, change of the behavior of frames due to adding damping devices to frames is taken into consideration and a non-linear static analysis computer program is developed . In numerical studies a few one and two story frames are used. The results of previous studies have shown that, adding energy damping devices to the structural systems, results in structure damping increase, story drift and base shear decrease. To reveal the behavior of the new bracing system, experimental and numerical studies are made. The main point in design of this bracing system, was the capability of easy replacement and maximum damping with minimum damage. It must be declared that design thought of this... 

Detection and classification of arrhythmia is important especially for patients in Emergency care units. Early diagnosis of cardiac arrhythmia makes it possible to choose appropriate anti arrhythmic drugs, and is thus very important for improving arrhythmia therapy. Computer-Assisted Diagnostic (CAD) Systems are used in recent decades in which extracted features and classifiers are the most important factor. In this project, we try to focus on both of these two major factors in heart arrhythmia classification using HRV signal. Therefore, in this project, we try to classify different groups of arrhythmia using HRV signal processing especially the nonlinear processing. Our main aim is to... 

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... 

In this M.Sc. thesis dynamics of a system of 3-D fluid (internal) and solid interaction hase been studied. Structure (shell) filled with dense fluid (liquid) and it is under large amplitude vibrations excitations. Shell is analized using geometrical nonlinear general shells formulations. The nonlinear analysis includes large displacements, large rotations and large strains without considering material nonlinearity. Based on the potential flow assumption the governing equations of fluid are derived. And using boundary elements formulations fluid hydrodynamic pressure in each step is drived. In order to simultaneous and mutual influence of fluid and structure, numerical model of combined... 

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... 

This research introduces two new passive control devices for protecting structures against earthquakes: Dual Pipe Damper (DPD) and In-filled Pipe Damper (IPD). The DPD device consists of two welded pipes. The IPD device is a DPD with two smaller pipes inside them and the spaces between the pipes are filled with metals such as, lead and zinc. The DPD device only utilizes plastic deformation of pipes; but the IPD device takes advantage of plastification of the outer and inner pipes, the in-filled metals, and the friction between metals as energy absorption mechanisms. Quasi-static cyclic tests are performed on four specimens of DPD and six specimens of IPD all showing stable hysteresis and... 

Ordinary structures absorb a large amount of input energy by structural elements whereas failure in these elements causes a huge loss in structure and it’s really difficult to repair or unrepairable. Nowadays a wide range of metallic dampers is used in structures as fuse elements. this research evaluates the response of structures that are equipped with a novel steel damper named Telescopic Lead Yield Damper (TLYD) which was introduced by Eskandari in 2018. As TLYD has a different yielding plateau it can tolerate large deformations. In this research firstly this novel damper was introduced and the performance of the damper under cyclic loading was demonstrated. Then a numerical model of 6,... 

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... 

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... 

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 recent years using concrete and steel together in buildings and bridges to mix their advantages and compensate disadvantages is very common especially in seismic zones. Using Concrete Filled Steel Tubular (CFST) columns is one of these methods. In these columns, steel tube has longitudinal and lateral reinforcement role for helping concrete core to resist against bending moment, shear and tension. Steel tube also creates confinement in concrete and increase compressive strength and prevents concrete from spalling. Concrete core increases stiffness of column and reduces capability of inward local buckling. Behaviors of CFST columns are influenced by loading, characteristics of materials...