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Introduction of Concentric Braced Frame Equipped with BRB & YE (yielding element) and Quantification of Seismic Perfomance Factors
Based on FEMA-P695
,
M.Sc. Thesis
Sharif University of Technology
;
Mofid, Massoud
(Supervisor)
Abstract
This investigation is intended to assess the behavior of SCBFs in the presence of typical brace members, which buckles in compression, and BRBs joining by yielding elements. While braces play a role in providing stiffness for structure, central yielding elements will act as energy-absorbing fuses. In this frame type, energy dissipation will mainly be undertaken by BRBs and yielding elements. The mentioned yielding elements do this by initiating plastic hinges in each corner of the central frame. As it is clear, designing a structure that includes the stated lateral-load-resisting system necessitates seismic performance parameters to be evaluated. Hence, by pursuing the FEMA P695 methodology,...
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...
Parametric Study on Seismic Performance of Spherical RC Domes
, M.Sc. Thesis Sharif University of Technology ; Vafaei, Abolhassan (Supervisor) ; Mofid, Massoud (Co-Advisor)
Abstract
The present parametric study discusses the effective factors on seismic performance of spherical RC domes. For this perpose, a series of domes with different spans, a variety of contact angles (the angle between the bottom of the sphere and the center of the sphere), openings with different areas and various support condition are studied. Then the value of response modification factor and it's components is determined to take into account the effect of each component. The results obtained indicated that the response modification factor increases as the contact angle enhances. However, the span of domes insignificantly affects the value of response modification factor.also analysis on domes...
A Parametric Study on Application and Analysis of Beam to Column "Reversed Channel" Connection in Tubular Systems
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Today steel tubular systems are used more than before, especially in recent years. A difficulty with this type of systems is making beam to column connections using bolts due to no access to holes of bolts from the inside of tube or hollow circular column. Reverse channel connection is devised and introduced to prevail this problem. Access to holes in this connection is from the inside of channel. In this connection, the web of the channel is connected to steel beam using bolts and the two legs of channel is welded to face of tube column.
This type of connection does include some innovations; not too many researchers work on different versions of this connection. This thesis provides an...
This type of connection does include some innovations; not too many researchers work on different versions of this connection. This thesis provides an...
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...
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....
Parametric Study of Concrete Connection Retrofitted by Steel Jacketing
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
This study investigates the cyclic experimental behavior of damaged exterior reinforced concrete beam–column joint specimens retrofitted with the proposed technique using steel elements called steel prop and curb. The technique is usable for local and global strengthening of reinforced concrete frames. Four half-scale RC joints were tested under the cyclic loading; two control specimens with the different beam heights were loaded up to their ultimate strength and this was followed by retrofitting of these damaged specimens as new specimens and tested again under the same loading system. This study indicate the importance of some parameters such as friction , jacket place , thickness of plate...
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...
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...
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...
Design, Modeling and Investigation of Seismic Behavior of Bracing Type Steel Shear Panels
, Ph.D. Dissertation Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
So far a number of solutions have been proposed to resolve some problems of steel plate shear walls including large induced loads on the surrounding members, late panel’s yielding along with lack of openings. One of the forms that can be considered for steel shear walls is braced shear panels.Regarding to the many advantages of this structural system, in this thesis steel shear panels with concentric or eccentric bracing have been introduced. For this purpose, first a procedure for plastic analysis and design, aiming to develop a predetermined collapse mechanism, is proposed. The results demonstrate that the closed-form analytical equations along with the extension of failure mode control...
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...
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...
Crack Localisation In Homogeneous Plates by Analyzing the Dynamic Responses of the Plate Excited by the Moving Load
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor) ; Nikkhoo, Ali (Co-Supervisor)
Abstract
The purpose of the study: The purpose of this study is to identify the crack position in homogeneous plates through health monitoring methods based on vibration. Identifying structural damage is one of the issues that attention can prevent the sudden collapse of structures and causing heavy loss of life and property. For this reason, extensive studies have been conducted in this field in recent decades. In this study, plates are examined as one of the most used structural members, and their damage is identified through a proposed method based on wavelet transform. Research method: In this study, through the wavelet transform method, the dynamic responses of a homogeneous plate excited by a...
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...
Nonlinear Behavior of Buckling Knee Bracing and a New Design Method for Multi Story Structures
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
New CKB system is implemented into the multistory frames and investigated how its ductility and energy absorption will be changed if its bracings are able to buckle.buckling braces can improve energy absorption of lateral systems with their post-buckling characteristics through cyclic motions of frames.in proceeding,Nonlinear behavior of multi-story CKB systems within a non-dimensional desigh graphs is presented.application of multi-linear behavior of these systems are controlled by checking their ductility demands and their capacity. Nonlinear dynamic response of multi-story CKB system is analyzed through FEM softwares and presente through curves with which designers can calculate...
Developing of MIDA Method in Irregular Structures in Plan with Concentrated Plasticity Model
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In this research, modal incremental dynamic analysis (MIDA) has been investigated on three-dimensional structures with irregular plans. The MIDA method is an incremental static analysis that considers higher modes of the structure. In fact, it is a combination of modal pushover (MPO) and incremental dynamic analysis (IDA) methods that incorporate the advantages of both and is much faster than the IDA method. Compared to constant analyses, incremental analysis is more extensive in terms of results and response to earthquakes. Due to the uncertainties in the nature of future earthquakes, engineers use the IDA method to achieve a broader view of the structure's response under potential...
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...
Effect of Efficient Management on Reconstruction of Apartment Buildingsi n Region 1 of Tehran City Using Hierarchical Analytical Model
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Nowadays population growth, people housing demand and urbanization tendency has increased the land and house prices. So the constructers tend to build apartments. Time consuming and heavy costs of building and renovation has made the owners to rebuild the damages of their houses in case of an accident. Time and cost are the main factors in construction which includes rebuilding. Buildings and especially apartments renovation is expensive and prolonged. So the rebuilding tendency has been noted more than ever. In this study it has been tried to control costs and time by efficient management to save the rebuilding time and money. Two kinds of questionnaire has been applied to study different...
Dynamic Response of Concrete Funicular Shells under Impulse Loads
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor) ; Mofid, Massoud (Co-Advisor)
Abstract
Reinforced concrete shells are widely used to cover the small to large area with more aesthetics at minimum cost. Shell structures carries 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 forced vibration of funicular shells on a rectangular ground plan under impulse loads using shallow shells theory. Two boundary conditions, simply supported and clamped, are considered. Displacement components are product of position and time functions. The analysis is based on the expansion of displacement...