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Seisimc Performance of Dutile End Diaphragms For Slab-on-girder Steel Bridges
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
This thesis illustrates the typical seismic retrofitting of bridges using a model governing transverse seismic response of retrofitted bridges by simplified analytical models of the end diaphragms based on the fundamental dynamic concept as well as previous research works. For three types of ductile diaphragm devices such as Eccentrically Braced Frames (EBF), Triangular-plate Added Damping and Stiffness Devices (TADAS) and Chevron Knee Bracing (CKB)and Shear Panel System(SPS), finite element nonlinear analytical models are developed in separate flexural and shear yielding modes, and the capability of the proposed finite element models is ascertained.The IDA (Incremental Dynamic Analyses) are...
Investigation and Modeling of a New type of Semi-Rigid, Steel Beam-Column Connection under Monotonic Loading
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
This thesis presents the investigation and development of a Finite Element Model (FEM) for a new type of Beam-Column Semi-Rigid steel connection. One of the main parts of this connection is a steel T profile inserted on top of a beam connecting it to a column by bolts. It seems that changes in the geometry of the T profile and its bolt positions can have a great influence on the rigidity or flexibility of the connection. Therefore, meaningful categories of the T profile geometry with different bolt positions have been modeled and analyzed by means of a Finite Element Modeling software ABAQUS, and their moment-rotation curves were driven. Also the Initial and Nonlinear Stiffness and the...
Response Modification Factor of Steel Plate Shear Wall in Steel Structures
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Steel shear wall systems have been introduced as a lateral load resisting system since 1970s. Based on the designer’s choice, this system can be used with or without stiffeners. Employing stiffeners prevents the elastic buckling of steel plates which can enhance the system to absorb more energy. The design code for using stiffeners has not developed yet in Iran since this kind of systems is not common practice. In this study, the Response Modification Factor (R), as an important factor in the design procedures of structures, is investigated for 1,3,5,7 and 10-story regular and irregular building structures which have un-stiffened steel shear walls with 3, 4.5 and 6 millimeters thickness with...
Response Modification Factor of Steel Plate Shear Walls in Concrete Structures
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
The Steel shear wall is one of resisting lateral load system which has been used since 1970.with respect to design we can apply this system with or without stiffeners .here our investigation is about steel shear wall without stiffeners. Also this system is called SSW. Since using this system is new fashion, there is no specific code for it in Iranian 2800 code .also there is no code for using this system in reinforced concrete frames in any code which makes this investigation much harder. Need to obtain R which is one of the most important seismic parameters, encouraged us to consider R for SSW in 3 to 7 storey structures .we obtained static pushover curves with nonlinear static analysis...
On the Characteristic and Behavior of Concrete Structure with Steel Knee Hat Brace
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Nowadays, the knee bracing system (KBF) takes civil engineer’s attention because of its benefits and properties. This new form of framing is constructed through the knee and the diagonal brace elements. The knee part is a fuse-like component that dissipates energy by the formation of plastic flexural and/or shear hinge, when the building is subjected to severe lateral loads. In this system, the diagonal brace provides most of the lateral stiffness. Also the flexural or shear yielding of the knee element provides the ductility under a severe earthquake. In this way, the damage is concentrated in a secondary member, which can be easily repaired at minimum cost. Floor distortions are reduced...
Parametric Studies of Seismic Behavior of Single Story Concrete Frame Equipped on Yielding Element
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In this thesis, in order to evaluate the vulnerability of concrete structures equipped with Yielding Element (YE) against earthquakes, two single story/ span concrete frames with different bay-to-height ratios (B/H<1 and B/H>1) are considered. Since the nature of earthquakes is to release energy due to tectonic movements in the earth and the nature of damages in structures depends on the rate of absorbed energy, investigating the behavior of structures are based on the energy concept which is considered as the most important way to design structures against earthquake load. In order to provide seismic resistance against earthquakes and reduce the damages in main elements, it is required to...
A Parametric Study on Seismic Behavior of Multi-Story Steel Frames Equipped with Yielding Elements Using FEM
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In this Thesis Project the Behavior of Multi-story Steel Frames Equipped with Yielding elements has been investigated and analyzed. These elements act against severe earthquakes like fuse and cause dissipation in main part of input energy of structure. The position of these elements are at the cross point of braces. The most advantages of yielding elements in steel frames are ease to use and ability to replace after earthquake The main idea in this research is the effect of number of stories in buildings which are equipped with yielding elements.3,7 and 10-story steel frames with 3 bays and 15,20 and 25-story steel frames with 5 bays are the models for this investigation. At the first part...
Parametric Study of Simple Column-Base Connections under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Column-base connections are one of the most important elements in steel structures which connect the steel frame to the foundation. Therefore, in structures erected in seismic areas, these connections are critical to convey cyclic inertia forces to the frame. In this research the author performed a parametric study utilizing Finite Elements Method (FEM) to investigate the connection’s cyclic behavior. Primarily, the modeling method is verified and calibrated by the use of available experimental data. Afterwards, the parametric computer models are made. Though some researchers have investigated similar connection types, some components’ parameters like the column’s dimensions have not been...
Study and Design of a New Kind of Knee Bracing in Semi-Height Multi-Story Steel Building
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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...
Examining Steel Plate Shear Wall with Various Infill Plates Under Cyclic Loads
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In the present study, a number of Steel Plate Shear wall (SPSW) models with various infill plates such as perforated and slit infill panels are analyzed and the results are utilized to discuss about behavior of Steel Plate Shear walls with various infill plates. The ABAQUS finite element package is utilized for all Eigen value and incremental nonlinear pushover analyses. Cyclic loading is in compliance with the ATC 24 loading protocol (ATC 1992). To validate modeling, boundary conditions and loading procedures, the experimental results provided by Darren Vian et al. [102, 103] and In-Rak et al. [48, 49] was modeled and analyzed. Investigation of steel plate shear walls made of different...
Quantification of Seismic Performance Factors of Y-Bracing
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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...
The Assessment of Joint's Rigidity Effect on the Nonlinear Dynamic Behaviour of Steel Frames with Semi-Rigid Connections
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In this thesis project the effect of joint rigidity on the behavior of steel braced frames has been investigated. In order to carry out this study on the efficiency of semi-rigid connections, a series of 3-bay braced frames ranging from 6- to 20-story with extended end-plate and flush end-plate connections have been selected and designed. This study has been extended by evaluating the role of the mentioned connections on seismic performance of selected semi-rigid frames under seven famous earthquake records. Having taken a particular performance level, in this case, “life safety” the target displacement and also the lateral load pattern for each frame have been calculated. Then using a...
Modeling of Cohesive Crack Propagation in Saturated and Semi Saturated Porous Media
, Ph.D. Dissertation Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Mofid, Massoud (Supervisor)
Abstract
Modeling the water flow in cohesive fracture is a fundamental issue in the crack growth simulation of cracked concrete gravity dams and hydraulic fracture problems. Discontinuities in porous materials such as concrete, soil and rock have important role on the mechanical and hydraulic behavior of a multiphase system. The creation and propagation of discontinuities, such as cracks in a multi-physics system, lead to a complex non-linear coupled problem with continuous topological changes in the domain.In this study, a mathematical model is presented for for the analysis of dynamic fracture propagation in the saturated and semi-saturated porous media. The solid behavior incorporates a discrete...
Dynamic Analysis of Timoshenko Beam with Nonuniform Cross Section and Kirchhoff Plate with Nonuniform Thickness Under Moving Mass
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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...
Estimating the Seismic Reliability of the Structures Based on Modal Nonlinear Probabilistic Analysis
, Ph.D. Dissertation Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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,...
On the Parametric Study of Tall Buildings with Different Lateral Force Resisting Systems
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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....
Seismic Design of Substation Structures with Consideration of IEEE-693
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
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...
Seismic Performance Evaluation of Vertcial Irregular Structures through Nonlinear Time History Analysis
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Incremental Dynamic Analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Using IDA , the objective is to study the effect of the irregular distribution of stiffness and strength along the height of a 9 story 3D steel structure model. The reference and each modified structure are hence forced to show the complete spectrum of behavior from elasticity to final global instability, allowing the estimation of capacities for the full range of limit-states and enabling a straightforward comparison without needing to “tune” the structures to the same fundamental period and/or the...