Sharif Digital Repository

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... 

Reinforced concrete shells are widely used to cover the small to large area with more aesthetics at minimum cost. Shell structures carry load through their shape rather than material strength. Funicular shells are special type of shells that their shape is obtained so that stresses be compressive under a special load (for shell, this load is its dead weight). This study deals with geometrically nonlinear vibration of funicular shells on a rectangular ground plan under impulse loads using nonlinear shallow shells theory. The boundary conditions are considered as clamped edges. Displacement components are product of position and time functions. The analysis is based on the expansion of... 

In the recent years, neural networks have been used to solve many problems in different fields, specifically in engineering problems. Neural networks have different applications in material science and structures including modeling stress-strain relationship of composite materials and static and dynamic analysis of structures. Recently, a new method called neuro-finite element has been developed for nonlinear static analysis of structures manufactured by one-dimensional elements. In this method, by investigating the load-deflection diagram of each element, it is possible to analyze and produce a load-deflection diagram for the whole structure using neural networks. This experimental study... 

The considerable structural damage caused by near field earthquakes has revealed the need for further research on their characteristics and their corresponding effects on structures. The short-duration, high- energy pulses present in these types of earthquakes impose high demands on the structures compared to far field ground motions. Thus, more research is needed to improve the current design methods, especially from a performance based point of view for the structures close to faults. This study is about damage assessment of steel moment resisting frame structures under near-field ground motions from a performance based design point of view. A number of 3 and 9-story, 3-D structural model... 

Progressive collapse in the structures can be happened as a result of many events such as terrorist attack, planes or vehicle collision to the structures and etc. Researchers’ attention to this phenomenon after occurring progressive collapse in Ronan Point building attracted and by happening terroristic attacks in Alfred P. Murrah and WTC buildings, studies in this field has developed extensively, meanwhile some of the codes, including UFC 4-023-03 or GSA, have proposed general instructions and analytical methods for increasing the strength of the structure against progressive collapse. If the structure in this analysis, does not meet the acceptance criteria of the code, the structure must... 

Today, Progressive Collapse analysis of Structures has a great rule in predict and preventing of overall collapse of structures due to local damage to few elements. After World Trade Center collapse, Progressive collapse analysis became more important. According to better ductility of Concrete Filled Steel Tubular Columns, because of existence of core concrete confinement, it is prospected that using this type of columns will lead to better resistance against progressive collapse. In this study, structures with concrete filled steel tubular columns will be examined in progressive collapse. In addition, in this study, a numerical model was proposed to model concrete filled steel tubular... 

In conventional method of modeling and design of structures it is assumed that structures are fixedly supported, however, this assumption is generally far from reality; because, not only the majority of buildings’ bases are not stiff enough to suppose them rigid, but also if their foundations are shallow there exist no piles underneath them, they may separate from their bases – the event which is called foundation uplift. Although according to past studies permission of foundation uplift as well as incorporation of base flexibility may markedly affect any structure’s dynamic response, is spite of about half a century which has elapsed since the beginning of these studies, it seems that still... 

The AISC Seismic Design Provisions now include capacity design requirements for steel plate shear walls,which consist of thin web plates that infill frames of steel beams, denoted horizontal boundary elements)HBEs), and columns, denoted vertical boundary elements (VBEs). The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the... 

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... 

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... 

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... 

This study proposes a robust technique for large displacement analysis of slack cable structures subjected to dynamic loadings using a novel method, entitled Node Relaxation. Ordinary numerical methods are usually unable to analyze cable structures due to singularities arising from large displacements and rotations following any alteration of the applied loads. When dynamic loads are considered, handling these singularities in numerical analyses becomes even more challenging. In this thesis, an effective iterative method is proposed for three-dimensional large-displacement dynamic analysis of structures consisting slack cables as the primary load-bearing system. The cable structure is... 

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,... 

Conventional eccentric braced frames often sustain large residual deformations and significant damages after strong earthquakes which may lead to heavy damages or even destruction of the structure. Here, a self-centering, Y-inverted, eccentrically braced frame (SC-YEBF) is proposed which combines the lateral load resisting benefits of YEBF including strength, stiffness and energy dissipation capacity with the re-centering capacity of post-tensioned (PT) high strength steel strands used at beam-to-column connections. A design procedure is presented assuming that all the seismic input energy is dissipated through inherent damping and plastic deformations of the link-beams. Thus, in 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...