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local-buckling
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Effect of defects on the local shell buckling and post-buckling behavior of single and multi-walled carbon nanotubes
, Article Computational Materials Science ; Volume 79 , November , 2013 , Pages 736-744 ; 09270256 (ISSN) ; Mohammadi, S ; Khoei, A. R ; Sharif University of Technology
Abstract
The local buckling behavior of perfect/defective and single/multi-walled carbon nanotubes (CNTs) under axial compressive forces has been investigated by the molecular dynamics approach. Effects of different types of defects including vacancy and Stone-Wales (SW) defects and their configurations on CNTs with different chiralities at room temperature are studied. Results show that defects largely reduce the buckling stress and the ratio of immediate reduction in buckling compressive stress of the defective CNT to the perfect one, but have little influence on their compressive elastic modulus. SW defects usually reduce the mechanical properties more than vacancy defects, and zigzag CNTs are...
Structural integrity assessment of offshore jackets considering proper modeling of buckling in tubular members—a case study of resalat jacket
, Article Journal of Marine Science and Application ; Volume 21, Issue 4 , 2022 , Pages 145-167 ; 16719433 (ISSN) ; Sharif University of Technology
Editorial Board of Journal of Harbin Engineering
2022
Abstract
In the present research, results of buckling analysis of 384 finite element models, verified using three different test results obtained from three separate experimental investigations, were used to study the effects of five parameters such as D/t, L/D, imperfection, mesh size and mesh size ratio. Moreover, proposed equations by offshore structural standards concerning global and local buckling capacity of tubular members including former API RP 2A WSD and recent API RP 2A LRFD, ISO 19902, and NORSOK N-004 have been compared to FE and experimental results. One of the most crucial parts in the estimation of the capacity curve of offshore jacket structures is the correct modeling of...
Investigation of Local Buckling in Marine Pipelines under External Pressure
, M.Sc. Thesis Sharif University of Technology ; Fallah Rajabzadeh, Famida (Supervisor) ; Seef, Mohammad Saeed (Co-Advisor)
Abstract
To keep up with the growing demands for energy, the oil and gas industry ventures into deeper waters. This increases complexity of offshore projects. Part of this complexity is due to the resistance of a pipeline against local buckling collapse due to external pressure that is more significant in higher pipe laying depth and consequently higher external pressure. Pipeline response to external pressure is an important factor in design of marine pipeline.Local buckling of a pipeline is the buckling behaviour within the pipeline cross section. Other types of buckling behaviour such as upheaval and lateralbuckling are not in the scope of this thesis.In this thesis, the installing pipeline is...
Nonlinear Analysis of Structures with Concrete Filled Steel Tubular Columns
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
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...
Investigation of Strength and Rotation Capacity of Box Column
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In this study, the behavior of box column subjected to constant axial load with cyclic lateral force have been investigated by Finite Element method. The resulf of FE anslysis are in a good agreement with experimental result in predicting of behavior and performance of box column. In order to investigation of behavior uses of some performance indices such as axial shortening, over strength, plastic hinge length, out of plane deformation and rotation capacity. The effect of significant parameter such as axial force to yield strength ratio, flange whidth to thickness ratio of flange, web whith to thickness ratio of web, global slenderness ratio and loading protocol on performance indices have...
Elastic interactive buckling strength of corrugated steel shear wall under pure shear force
, Article Structural Design of Tall and Special Buildings ; Volume 26, Issue 8 , 2017 ; 15417794 (ISSN) ; Mofid, M ; Aziminejad, A ; Emami, F ; Sharif University of Technology
Abstract
Different ways have been presented to prevent elastic buckling of steel shear walls. One of these solutions is corrugated shear wall. In this type of wall, shear buckling strength increases without increasing the thickness of the panel. Numerical modeling results indicate that, always, shear buckling strength of corrugated panels is more than the flat panels and with the right choice of the geometric parameters of corrugated panels; without increasing the thickness of the panel, we can improve buckling strength significantly. In the trapezoidal corrugated panels, reducing the width of the subpanels do not always increase buckling strength of the panel, but it changes the panel buckling shape...
Challenges in calculation of critical buckling load of tubular members of jacket platforms in finite element modeling
, Article Journal of Marine Science and Technology (Japan) ; Volume 25, Issue 3 , 2020 , Pages 866-886 ; Erfani, M. H ; Sayyaadi, H ; Sharif University of Technology
Springer
2020
Abstract
Accurate estimation of the capacity curve of offshore jacket structures to achieve performance levels and ductility is of great importance. Proper modeling of compressive members to correctly investigate global and local buckling is crucial in estimation of the capacity curve. Buckling modes and deformations due to local buckling can be considered, if the compressive braces are modeled by shell or solid elements. The purpose of this paper is to achieve the correct compressive behavior of braces with solid type elements and investigate the effects of five different parameters such as D/t, L/D, mesh size, mesh size ratio, and imperfections. ABAQUS FE software is used for this purpose. The...
Assessment of Performance Based Behavior of Steel Moment Resisting Frames
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In order to reduce structural and nonstructural damages and associated financial losses during intense seismic events such as Bam earthquake, seismic retrofitting of existing structures should be considered as a special issue. In this regard, for quantifying the seismic performance of structures a guideline termed “instruction for seismic rehabilitation of existing building No.360” is issued which is mainly borrowed from performance-based assessment procedures FEMA 356. In contrast to conventional seismic design methods which are based on controlling stress ratio for different load combinations, in performance-based earthquake engineering methodology, the displacement control of structural...
Effect of Local Buckling on Deformation Capacity of Steel Pipe Braces
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In this thesis, finite element (FE) models were developed to study hysteresis behavior of pipe braces subjected to cyclic loading. Thus steel braces previously tested by other investigators are used. The results of the analysis are in good agreement with the experiments. Besides, the FE analysis could also simulate both the overall and local buckling. As a result, a sharp growth in plastic strains is followed by geometric changes at the mid-span due to local buckling. The sharp growth of plastic strains is entitled as strain rises. In fact, the local buckling triggers rupture of braces at the mid-span. The local buckling initiation is identified by the sharp growth in plastic strains....
Investigation of Strain Jumping and Its Effect on Evaluating Capacity of Steel Bracing Deformations
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In this study, HSS and double angle braces subjected to cyclic loading in order to study the buckling and post buckling behavior have been investigated by Finite Element method. The results of FE analysis are fairly in good agreement with experiments. Analysis demonstrate that when local buckling occurs in middle span, subsequently, strain rises severely. Accordingly, this strain jumping causes early fracture in braces. Therefore, local buckling can be one of the primary reasons of fracture in braces. As a result, local buckling must be considered one of the primary limit state of Performance-Based design of steel braces. In addition, finding a way to predict local buckling can help us to...
Investigating Starin Growth in Concentric Braces and Specify the Start Time of Failure in Section
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In this Thesis, the behaviour of stell brace was studied in finite element models. In this section, a comparison between the results of these models and the results of experimental models which were done in past years, was carried out. It shows that these result is in good agreement with each other, Moreover it has been found that the primary cause of failure in the sample is local bucking and then change in the geometry of sample which will be followed by strain jumping in next cycles which shows the importance of local buckling due to the proximity of this event to strain jumps and can be accepted as braces limit state design.Finally, we try to predict the time of failure of samples with...
Effect of Post Buckling Rupture on the Deformation Capacity of Concentrate Braces
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
In this study the behavior of steel bracings under cyclic loading, is modeled with finite element method. Analysis have shown that after local buckling in plastic mid-span position, due to the severe geometry change, the strain grows rapidly, The sharp growth of plastic strains is entitled as strain rises. Geometry change created will cause the collapse brace speeding up. In fact, the main local buckling can be used as a determinative factor in performance base design for steel braces. So the thesis has been investigated, using the parameters fracture life to quantify local buckling and fracture. Also with using the CVGM model, the fracture of the brace could be predicted. The analytical...
The Effects of Local Buckling on Behavior of Steel Braces
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Steel Concentrically Braced Frames are common lateral load resisting frames. Poor design of this system can lead it to premature failure of braces. This failure may be due to non-elastic buckling of brace members or their connections. Design Codes divide Concentrically Braced frames into two groups: Ordinary Concentrically Braced Frames and Special Concentrically Braced Frames and for each, specific limitations have been determined for width to thickness ration and slenderness. Many of these limitation have been obtained on the basis of experimental tests. In this thesis steel braces behavior under cyclic loading is studied. For parametric investigation, Finite Element Method is used. Abaqus...
Numerical Study of Stiffener Effects on Composite Shear Wall Performance
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
Concrete filled double-steel-plate (CFDSP) composite wall is a new lateral resisting system that recently used in design and strengthening of high-rise buildings. This CFDSP composite wall is composed of concrete filled steel tubular columns at the two boundaries and concrete filled double-steel-plate wall body. The main advantage of this system is the interaction between steel and concrete which delays local buckling of steel plates. Also, steel jacket increases the strength of concrete in result of confinement effects. Furthermore, these systems have lower thickness compared to ordinary concrete shear walls. Hence, they have less structural weight which reduces the earthquake force....
Investigation of Local Buckling and Prediction of Fracture Onset in Hollow Section Steel Beams
, M.Sc. Thesis Sharif University of Technology ; Alijani Moghaddam, Hassan (Supervisor)
Abstract
In this study, the behavior of cantilevered HSS beams under cyclic bending loading are modeled in order to study the buckling and post buckling behavior have been investigated by Finite Element method.The analytical results are fairly in good agreement with the experimental results. The analysis demonstrates that when local buckling occurs in near of connection area, subsequently, the strain grows severely that is entitled as strain rise and then, is caused fracture. As a result, local buckling limits the ability of these members to form stable plastic hinges and the behavior is highly dependent on the width-thickness (b/t) and the depth-thickness ratio (h/t).Also, the thesis has been tried...
Performance of buried gas distribution pipelines subjected to reverse fault movement
, Article Journal of Earthquake Engineering ; 2017 , Pages 1-24 ; 13632469 (ISSN) ; Rahimzadeh Rofooei, F ; Khajeh Ahmad Attari, N ; Sharif University of Technology
Abstract
In the current work, the results of full-scale laboratory testing of 114.3 and 168.3 mm in diameter steel gas distribution pipes buried at different depths and in two different soil types under a reverse fault offset of 0.6 m are presented and discussed in terms of longitudinal strain distribution, pipe deformation, and cross-section distortion. Results show that the pipe deformation and accordingly its failure mode, and soil failure planes change with increasing burial depth. It was also found that severe cross-section distortion occurs at about 2.3 times the strain limit for onset of wrinkling suggested by various guidelines. © 2017 Taylor & Francis Group, LLC
Performance of buried gas distribution pipelines subjected to reverse fault movement
, Article Journal of Earthquake Engineering ; Volume 22, Issue 6 , 2018 , Pages 1068-1091 ; 13632469 (ISSN) ; Rahimzadeh Rofooei, F ; Khajeh Ahmad Attari, N ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
In the current work, the results of full-scale laboratory testing of 114.3 and 168.3 mm in diameter steel gas distribution pipes buried at different depths and in two different soil types under a reverse fault offset of 0.6 m are presented and discussed in terms of longitudinal strain distribution, pipe deformation, and cross-section distortion. Results show that the pipe deformation and accordingly its failure mode, and soil failure planes change with increasing burial depth. It was also found that severe cross-section distortion occurs at about 2.3 times the strain limit for onset of wrinkling suggested by various guidelines. © 2018, © 2018 Taylor & Francis Group, LLC
Challenges in calculation of critical buckling load of tubular members of jacket platforms in finite element modeling
, Article Journal of Marine Science and Technology (Japan) ; 2019 ; 09484280 (ISSN) ; Erfani, M. H ; Sayyaadi, H ; Sharif University of Technology
Springer Tokyo
2019
Abstract
Accurate estimation of the capacity curve of offshore jacket structures to achieve performance levels and ductility is of great importance. Proper modeling of compressive members to correctly investigate global and local buckling is crucial in estimation of the capacity curve. Buckling modes and deformations due to local buckling can be considered, if the compressive braces are modeled by shell or solid elements. The purpose of this paper is to achieve the correct compressive behavior of braces with solid type elements and investigate the effects of five different parameters such as D/t, L/D, mesh size, mesh size ratio, and imperfections. ABAQUS FE software is used for this purpose. The...
Challenges in calculation of critical buckling load of tubular members of jacket platforms in finite element modeling
, Article Journal of Marine Science and Technology (Japan) ; 2019 ; 09484280 (ISSN) ; Erfani, M. H ; Sayyaadi, H ; Sharif University of Technology
Springer Tokyo
2019
Abstract
Accurate estimation of the capacity curve of offshore jacket structures to achieve performance levels and ductility is of great importance. Proper modeling of compressive members to correctly investigate global and local buckling is crucial in estimation of the capacity curve. Buckling modes and deformations due to local buckling can be considered, if the compressive braces are modeled by shell or solid elements. The purpose of this paper is to achieve the correct compressive behavior of braces with solid type elements and investigate the effects of five different parameters such as D/t, L/D, mesh size, mesh size ratio, and imperfections. ABAQUS FE software is used for this purpose. The...
Formation and Development of Plastic Hinges in Structures With Concrete Filled Steel Tubular Columns Using Nonlinear Static Analysis
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
concrete-filled steel tube offers many practical advantagescompared withconventional structural systems. The concrete infill provides stiffness and strength in compression and restrains local and global buckling. The inelastic deformation capacity of the CFT system is increased by the confinement of the concrete fill by the thin, ductile steel tube, and this significantly contributes to the seismic performance.
In this research, Formation and development of plastic hinges in CFST frames using pushover analysis was investigated. Different frames with rectangular and circular column and I beam weredesigned and Using nonlinear finite element analysis, interaction between steel and concrete...
In this research, Formation and development of plastic hinges in CFST frames using pushover analysis was investigated. Different frames with rectangular and circular column and I beam weredesigned and Using nonlinear finite element analysis, interaction between steel and concrete...