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Three-dimensional geometrically nonlinear analysis of slack cable structures
, Article Computers and Structures ; Volume 128 , November , 2013 , Pages 160-169 ; 00457949 (ISSN) ; Sharif University of Technology
2013
Abstract
An effective iterative method is proposed for three-dimensional large-displacement analysis of structures consisting of slack cables as the primary load-bearing system. This approach takes advantage of substructuring technique that is specially tailored to address the analysis and form-finding problem of slack cables subjected to arbitrary loads, and to reduce the overall analysis costs. At the overall structural level, a robust procedure is employed for detecting the instabilities and limiting the corresponding incremental displacements. The effectiveness of the proposed method for the analysis of highly unstable or variable-form structures is demonstrated by a number of analysis examples...
Progressive Collapse Due to Sudden Column Removal in Steel Moment and Eccentric Braced Frames
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor) ; Kazemi, Mohammad Taghi (Co-Supervisor)
Abstract
With increasing population and lack of habitable spaces, the building heights increased in cities around the world. Placing components of a structure in tandem may cause a permanent failure of the members due to strength reduction. During recent years, this kind of failure occurred in different places of the world, and is called progressive collapse. There are some various samples of the progressive collapse which all are good samples of failures such as building failure in Ronan Point in the UK, Twin Towers or the world trade center in NY, and Pentagon building. According to these issues, different institutions codified guidelines and codes in this field such as Department of Defense as DoD...
Influence of Soil-Structure Interaction on Collapse Margin Ratio
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
This thesis reveals the influence of soil-structure interaction (SSI) on the collapse potential of structures and also investigates the change in collapse margin ratio (CMR) of structures for which the design base shear has been reduced based on the soil-structure interaction provisions. According to the properties of structures and seismic excitations, SSI can increase, decrease or make no change in the response of structures. Based on seismic design codes for fixed-base structures, SSI causes reduction in design base shear of buildings. These provisions are based on linear behavior of structures. But under strong ground motions, specially at collapse level, structures can experience strong...
Collapse Capacity Assessment of Irregular Tall Buildings Considering the Effect of Pulse-Like Forward Directivity Ground Motions
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
Structural response to near fault ground motions has received significant attention in recent years. Such ground motions are different from ordinary ones and are characterized by a large, long period, velocity pulse caused by the forward directivity. These velocity pulses could potentially impose sever demands on structures and increase their risk of seismic collapse. The situation could even be worse for tall buildings with fundamental periods close to the period of the velocity pulses, and requires special consideration in design process. Prediction of seismic-induced collapse potential of structures has been among the main concerns in Performance Based Earthquake Engineering (PBEE). The...
Collapse Analysis of Infilled Steel Frames by Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
In many urban and rural areas, steel frames are infilled by masonry materials such as bricks. The resulting structural system is commonly known as an infilled frame. Nonlinear analysis of infilled frames using conventional analysis methods, such as incremental dynamic analysis (IDA), requires high levels of modeling complexity and computational effort, therefore in most practical cases; the infill panel is often neglected. Such an approximation results in a high level of inconsistency in evaluation of the actual behavior (e.g. lateral strength and stiffness) of these frames. Introducing more simple and straightforward methods of analysis and design for these frames, can be a solution to this...
Investigation of Progressive Collapse Resistance of RC Structures Retrofitted at Joints by FRP Sheets
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
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...
Progressive Collapse Analysis of Structures with Concrete Filled Steel Tubular Columns
, M.Sc. Thesis Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
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...
Assessing and Fragility Analysis of Collapse of R.C Buildings
, Ph.D. Dissertation Sharif University of Technology ; Ghaemian, Mohsen (Supervisor)
Abstract
Global collapse in earthquake engineering refers to the inability of a structural system to sustain gravity loads when subjected to seismic excitation. Dynamic instability phenomena in exist buildings have a key position and for this reason strict criteria in structural seismic assessing codes presented for avoiding this phenomena. At this study, dynamic instability of five designed concrete buildings with moment frame system, mixed up 3, 6, 9, 12 and 15 story building, are investigated. P-delta effects, deterioration in strength and stiffness and cyclic deterioration in structural components considered in this investigation. For modeling nonlinear behavior of elements, experimental results...
Modeling of Mixed Hinges and Their Use in the Inelastic Analysis of Frames
, Ph.D. Dissertation Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
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...
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...
Plastic Analysis of Two Dimensional Frames using Ant Colony Algorithms
, M.Sc. Thesis Sharif University of Technology ; Jahanshahi, Mohsen (Supervisor)
Abstract
In previous decades, easy access to material and low cost human power allow the product process to be performed in a preferred way. The limit in amount of material, economy, and the efficiency of the model has not been influential like these days. Today, the effective use of material and consideration of an economic model have great importance. It is obvious that a process of designing implies optimizing which the range of its using is also continuing in many engineering sciences. Many optimization issues contain discrete nature. Many of searching spaces that we encounter in the real world applications are not necessarily continuous as a condition which has crucial importance for classic...
Assessment of the Hydro-Mechanical and Shear Behavior of Collapsible Soils by Using Suction- Controlled Triaxial Apparatus- A Case Study: Loess of Gorgan
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
In geotechnical engineering, collapsible soils as a part of problematic soils has an extreme importance since as a mutual effects of applying load and increasing their water content, Soil’s inter-particle forces become weak, and therefore, the soil experiences sudden large volumetric change known as collapse. Foundations built on these soils might experience sudden, large settlement. Collapsible soils exist in almost all continents, and many damages are reported due to the collapse phenomenon of these soils.
Due to the importance of this issue, and lack of comprehensive studies related to the volumetric and shear behavior of these soils, in this study, triaxial wetting test are performed...
Due to the importance of this issue, and lack of comprehensive studies related to the volumetric and shear behavior of these soils, in this study, triaxial wetting test are performed...
Nonlinear Dynamic Analysis of Lightweight Slack Cable-net Structures
, Ph.D. Dissertation Sharif University of Technology ; Dolatshahi, Kiarash (Supervisor) ; Ahmadizadeh, Mehdi (Supervisor)
Abstract
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...
Numerical Simulation of Liquid Jet and Bubble Collapse Interaction near the Wall
,
M.Sc. Thesis
Sharif University of Technology
;
Javadi, Khodayar
(Supervisor)
Abstract
Bubble collapse near a rigid wall with rapid and non-spherical compression of the internal gas can lead to destructive and unfavorable effects such as erosion, noise, and a fall-off in the performance of devices. Despite the fact that several investigations on this phenomena have been carried out under various conditions, studies indicate that the collapse of a single cavitation bubble next to the liquid jet injected from the wall's side and their interaction have not been studied so far. To achieve this goal, the present study deals with the three-dimensional simulation of the two-phase flow field from the Eulerian point of view. OpenFOAM has been used to solve the equations of conservation...
Integrating constrained random waves in endurance time analysis of offshore structures subjected to sea waves
, Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 1 July 2012 through 6 July 2012 ; Volume 2 , July , 2012 , Pages 677-684 ; 9780791844892 (ISBN) ; Estekanchi, H ; Zeinoddini, M ; Golestani, M ; Sharif University of Technology
2012
Abstract
This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach, the offshore structure is simulated in time-domain under a set of calibrated intensifying wave functions. They are devised to represent a gradually increasing roughness of the sea state by time. A performance index such as base shear, drift or stress in a critical structural members are monitored until they reach to a predefined maximum value. A...
Collapse assessment of steel moment frames using endurance time method
, Article Earthquake Engineering and Engineering Vibration ; Volume 14, Issue 2 , 2015 , Pages 347-360 ; 16713664 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Institute of Engineering Mechanics (IEM)
2015
Abstract
In endurance time (ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specified spectrum, intensifies with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis (IDA) results. It is shown...
Quantification of Seismic Performance Factors and Ductility of Off-Center Bracing System Composed of Buckling-Restrained Brace Elements
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
This project aims to determine seismic performance coefficients of Off-Center Braced lateral load resisting system (OBS) equipped with Buckling-Restrained Braces (BRBs), along with comparing its seismic performance in extreme seismicity level with those of Special Moment Frame (SMF). For this intent, the structural design of 24 regular-in-height residential OBS-BRB models was first carried out following ASCE7-16. Then, Static (Pushover) and Incremental Dynamic Analysis (IDA) were performed on the models using the methodology of FEMA P-695 to obtain the target coefficients. Furthermore, the coefficients were used for Pushover and IDA analysis of 27 irregular-in-height OBS-BRB models with soft...
Predictive Equations for Shear Link Modeling Toward Collapse
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise...
Seismic Hazard Assessment in the Lifetime Duration of Steel MRF Structures Considering Aftershocks
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourstekanchi, Homayoon (Supervisor)
Abstract
Following a large earthquake, numerous aftershocks can be triggered due to the complex stress interaction between and within tectonic plates. The aftershocks have the potential to cause severe weakening of mainshock-damaged buildings, threaten life safety, hamper reoccupation and restoration of buildings, and increase financial loss. The probability of aftershocks has not been included in the description of seismic hazard in performance-based earthquake engineering. This study proposes methodologies and a framework to investigate the seismic performance in the lifetime of steel MRF structures subjected to mainshock-aftershock sequences. The case studies correspond to three SAC 2D steel MRF...
Risk-based Approach to Account for Soil-Structure Interaction in Seismic Design of Building Structures
,
Ph.D. Dissertation
Sharif University of Technology
;
Ghannad, Mohammad Ali
(Supervisor)
;
Mahsuli, Mojtaba
(Supervisor)
Abstract
This paper proposes a novel probabilistic approach to account for soil-structure interaction (SSI) in the seismic design of building structures. In this approach, an SSI response modification factor, RSSI, is introduced to capture SSI effects on the seismic performance of structures. The proposed procedure quantifies RSSI such that the probability distribution of the collapse capacity of the structure designed to account for SSI concurs with that of the structure designed using the default fixed-base provisions. The proposed approach is employed for special steel moment frame buildings with surface foundation. A surrogate single degree of freedom (SDOF) system is developed in this study and...