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Author: Ahmed Mohsen Abd El Fattah
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The analysis of concrete columns using unconfined concrete models is a well established practice. On the other hand, prediction of the actual ultimate capacity of confined concrete columns requires specialized nonlinear analysis. Modern codes and standards are introducing the need to perform extreme event analysis. There has been a number of studies that focused on the analysis and testing of concentric columns or cylinders. This case has the highest confinement utilization since the entire section is under confined compression. On the other hand, the augmentation of compressive strength and ductility due to full axial confinement is not applicable to pure bending and combined bending and axial load cases simply because the area of effective confined concrete in compression is reduced. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength and ductility of concrete. Accordingly, the ultimate confined strength is gradually reduced from the fully confined value f[subscript]c[subscript]c (at zero eccentricity) to the unconfined value f[same as f1][subscript]c (at infinite eccentricity) as a function of the compression area to total area ratio. The higher the eccentricity the smaller the confined concrete compression zone. This paradigm is used to implement adaptive eccentric model utilizing the well known Mander Model and Lam and Teng Model. Generalization of the moment of area approach is utilized based on proportional loading, finite layer procedure and the secant stiffness approach, in an iterative incremental numerical model to achieve equilibrium points of P-[epsilon] and M-j response up to failure. This numerical analysis is adaptod to asses the confining effect in circular cross sectional columns confined with FRP and conventional lateral steel together; concrete filled steel tube (CFST) circular columns and rectangular columns confined with conventional lateral steel. This model is validated against experimental data found in literature. The comparison shows good correlation. Finally computer software is developed based on the non-linear numerical analysis. The software is equipped with an elegant graphics interface that assimilates input data, detail drawings, capacity diagrams and demand point mapping in a single sheet. Options for preliminary design, section and reinforcement selection are seamlessly integrated as well. The software generates 2D interaction diagrams for circular columns, 3D failure surface for rectangular columns and allows the user to determine the 2D interaction diagrams for any angle [alpha] between the x-axis and the resultant moment. Improvements to KDOT Bridge Design Manual using this software with reference to AASHTO LRFD are made. This study is limited to stub columns.
Author: Ahmed Mohsen Abd El Fattah
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The analysis of concrete columns using unconfined concrete models is a well established practice. On the other hand, prediction of the actual ultimate capacity of confined concrete columns requires specialized nonlinear analysis. Modern codes and standards are introducing the need to perform extreme event analysis. There has been a number of studies that focused on the analysis and testing of concentric columns or cylinders. This case has the highest confinement utilization since the entire section is under confined compression. On the other hand, the augmentation of compressive strength and ductility due to full axial confinement is not applicable to pure bending and combined bending and axial load cases simply because the area of effective confined concrete in compression is reduced. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength and ductility of concrete. Accordingly, the ultimate confined strength is gradually reduced from the fully confined value f[subscript]c[subscript]c (at zero eccentricity) to the unconfined value f[same as f1][subscript]c (at infinite eccentricity) as a function of the compression area to total area ratio. The higher the eccentricity the smaller the confined concrete compression zone. This paradigm is used to implement adaptive eccentric model utilizing the well known Mander Model and Lam and Teng Model. Generalization of the moment of area approach is utilized based on proportional loading, finite layer procedure and the secant stiffness approach, in an iterative incremental numerical model to achieve equilibrium points of P-[epsilon] and M-j response up to failure. This numerical analysis is adaptod to asses the confining effect in circular cross sectional columns confined with FRP and conventional lateral steel together; concrete filled steel tube (CFST) circular columns and rectangular columns confined with conventional lateral steel. This model is validated against experimental data found in literature. The comparison shows good correlation. Finally computer software is developed based on the non-linear numerical analysis. The software is equipped with an elegant graphics interface that assimilates input data, detail drawings, capacity diagrams and demand point mapping in a single sheet. Options for preliminary design, section and reinforcement selection are seamlessly integrated as well. The software generates 2D interaction diagrams for circular columns, 3D failure surface for rectangular columns and allows the user to determine the 2D interaction diagrams for any angle [alpha] between the x-axis and the resultant moment. Improvements to KDOT Bridge Design Manual using this software with reference to AASHTO LRFD are made. This study is limited to stub columns.
Author: Fatemeh Shirmohammadi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Accurate and realistic assessment of the performance of columns in general, and those in critical locations that may cause progressive failure of the entire structure, in particular, is significantly important. This performance is affected by the load history, pattern, and intensity. Current design code does not consider the effect of load pattern on the load and displacement capacity of columns. A primary research sponsored by Kansas Department of Transportation (KDOT) was conducted as the initial step of the present study (No. K-TRAN: KSU-11-5). The main goals of the KDOT project were: (1) investigation of new KDOT requirements in terms of the column design procedure and detailing and their consistency with AASHTO provisions; (2) verification of the KDOT assumptions for the plastic hinge regions for columns and bridge piers, (3) provide assessment of the load capacity of the existing columns and bridge piers in the light of the new specifications and using the new load demand as in the new provisions; and finally recommendations for columns and bridge piers that do not meet the new requirements. A conclusion was drawn that there is a need for conducting more studies on the realistic performance of Reinforced Concrete (RC) sections and columns. The studies should have included performance of RC members under various loading scenarios, assessment of columns capacity considering confinement effect provided by lateral reinforcement, and investigation on performance of various monotonic and cyclic material models applied to simulate the realistic performance. In the study reported here, monotonic material models, cyclic rules, and plastic hinge models have been utilized in a fiber-based analytical procedure, and validated against experimental data to simulate behavior of RC section under various loading scenarios. Comparison of the analytical predictions and experimental data, through moment-curvature and force-deflection analyses, confirmed the accuracy and validity of the analytical algorithm and models. The performance of RC columns under various axial and lateral loading patterns was assessed in terms of flexural strength and energy dissipation. FRP application to enhance ductility, flexural strength, and shear capacity of existing deficient concrete structures has increased during the last two decades. Therefore, various aspects of FRP-confined concrete members, specifically monotonic and cyclic behavior of concrete members confined and reinforced by FRP, have been studied in many research programs, suggesting various monotonic models for concrete confined by only FRP. Exploration of existing model performances for predicting the behavior of several tested specimens shows a need for improvement of existing algorithms. The model proposed in the current study is a step in this direction. FRP wrapping is typically used to confine existing concrete members containing conventional lateral steel reinforcement (tie/spiral). The confining effect of lateral steel reinforcement in analytical studies has been uniquely considered in various models. Most models consider confinement due to FRP and ignore the effect of conventional lateral steel reinforcement. Exploration of existing model performances for predicting the behavior of several tested specimens confined by both FRP and lateral steel shows a need for improvement of existing algorithms. A model was proposed in this study which is a step in this direction. Performance of the proposed model and four other representative models from literature was compared to experimental data from four independent databases. In order to fulfill the need for a simple, yet accurate analytical tool for performance assessment of RC columns, a computer program was developed that uses relatively simple analytical methods and material models to accurately predict the performance of RC structures under various loading conditions, including cyclic lateral displacement under a non-proportionally variable axial load (Esmaeily and Xiao 2005, Esmaeily and Peterman 2007). However, it was limited to circular, rectangular, and hollow circular/rectangular sections and uniaxial lateral curvature or displacement. In this regards, a computer program was developed which is the next generation of the aforesaid program with additional functionality and options. Triangulation of the section allows opportunity for cross-sectional geometry. Biaxial lateral curvature/displacement/force combined with any sequence of axial load provides opportunity to analyze the performance of a reinforced concrete column under any load and displacement path. Use of unconventional reinforcement, such as FRP, in lateral as well as longitudinal direction is another feature of this application.
Author: J. G. Teng
Publisher: John Wiley & Sons
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 280
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Book Description
Fibre-reinforced polymer (FRP) composites are used to strengthen reinforced concrete (RC) structures. A large amount of research now exists on this. This book brings together all existing research into one volume.
Author: Yi Ouyang
Publisher:
ISBN: 9781361031599
Category :
Languages : en
Pages :
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Book Description
This dissertation, "Nonlinear Analysis of Concrete Columns Under Non-uniform and Anisotropic Confinement" by Yi, Ouyang, 歐陽禕, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: For the past twenty years, more and more attention has been drawn to the "performance-based design" of structures due to the concerns of earthquakes, dynamic impact, wind loads and so on. As a result, the ductility of a building has become an important aspect on par with its strength. As far as construction material is concerned, concrete structures have been the most prevalent in these years. As a matter of fact, the ductility of concrete structures is inferior to that of steel structures. However, recent studies have proved that the confinement effect will improve the strength and the ductility of concrete. In traditional concrete construction, confinement is provided by transverse steel hoops placed inside the concrete members with certain spacings, i.e. discontinuously. New forms of concrete structures, such as concrete columns confined by fibre-reinforced polymer (FRP) and concrete-filled steel tubular (CFST) columns, are therefore proposed to enhance the efficiency of confinement, since the concrete in these structures is confined continuously. The mechanisms of uniform and isotropic confinement effect in FRP-confined concrete columns and CFST columns have been well studied, and the existing theoretical models can be applied to those typical load cases, such as FRP-confined circular concrete columns and circular CFST columns under axial compression. But the research on the mechanisms of non-uniform and anisotropic confinement effect is still evolving, in order to predict the behaviour of confined concrete columns with sections of various shapes under combined axial loads and bending moments. Usually finite element (FE) method is used to analyse such complicated problems. However, in a lot of current studies using FE method, the dilation angle of plastic flow of concrete is often treated as a constant, which does not reflect the observed behaviour of concrete regarding the variation of volumetric strain under triaxial compression. In reality, the volume of concrete will eventually expand due to the propagation of splitting cracks, and the true dilatancy of concrete should be non-linear. In this study, a new FE model is developed through Fortran 90 to account for the nonlinearity of the dilatancy of concrete, and verified against several load cases with non-uniform and anisotropic confinement effect, i.e. eccentrically loaded FRP-confined circular concrete columns, axially loaded FRP-confined rectangular concrete columns and eccentrically loaded CFST columns. Moreover, a simplified method is also proposed to provide quick estimations on the behaviour of circular CFST columns under eccentric compression. Subjects: Columns, Concrete - Testing
Author: ACI Committee 440
Publisher:
ISBN: 9781945487590
Category : Fiber-reinforced concrete
Languages : en
Pages : 110
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Author: Autar K. Kaw
Publisher: CRC Press
ISBN: 1420058290
Category : Science
Languages : en
Pages : 491
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Book Description
In 1997, Dr. Kaw introduced the first edition of Mechanics of Composite Materials, receiving high praise for its comprehensive scope and detailed examples. He also introduced the groundbreaking PROMAL software, a valuable tool for designing and analyzing structures made of composite materials. Updated and expanded to reflect recent advances in the
Author: M.P. Nielsen
Publisher: CRC Press
ISBN: 1439803978
Category : Science
Languages : en
Pages : 810
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Book Description
First published in 1984, Limit Analysis and Concrete Plasticity explains for advanced design engineers the principles of plasticity theory and its application to the design of reinforced and prestressed concrete structures, providing a thorough understanding of the subject, rather than simply applying current design formulas. Updated and revised th
Author: Wai-Fah Chen
Publisher: J. Ross Publishing
ISBN: 9781932159745
Category : Technology & Engineering
Languages : en
Pages : 500
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Book Description
J. Ross Publishing Classics are world-renowned texts and monographs written bt preeminent scholars. These books are available to students, researchers, professionals, and libararies.
Author: Steven D. Hart
Publisher:
ISBN:
Category : Columns, Concrete
Languages : en
Pages : 0
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Book Description
Over the past 30 years, FRP composites (carbon, glass, or aramid fibers) have arisen as a method of retrofitting existing reinforced concrete structures to bring them up to current code standards of confinement and ductility. The development of stress-strain models for FRP confined concrete began with the adaptation of steel confinement models then progressed to models specifically developed based on test results from FRP confined specimens. State of the art stress-strain models for FRP confined concrete models may now be validated against a wide variety of published experimental results. Recent publications show researchers branching out and looking at other aspects of FRP confined concrete behavior, including the impact of sustained service loads on long term and ultimate behavior. An experimental program which examines the effects of sustained service loading on the ultimate axial performance of FRP confined concrete is presented. The program's purpose is to determine whether or not a material model developed without the presence of a sustained load accurately predicts the ultimate stress-strain response of FRP confined concrete previously subjected to a sustained service load. Equipment and procedures were developed to model the critical events in a building life cycle: construction, sustained service loading, minor critical events, rehabilitation, and ultimate performance. Varying the order of these events produces a simulated life cycle allowing analysis of the impact of strain history on ultimate performance. The results of the experimental program indicate that the presence of a sustained service load changes the expected failure mode from FRP rupture to FRP de-lamination and the stress-strain response of a specimen is approximately 10% below published models when sustained service loads are included in the life cycle. A comprehensive modeling process is proposed for modeling significant events in a structure's life cycle. Impacts on earthquake engineering and reliability studies are addressed and future research suggested. This research shows that life cycle modeling can improve the design and rehabilitation of structures so that they meet safety requirements in future seismic events.
Author: Xiuli Du
Publisher: Springer Nature
ISBN: 9813349433
Category : Technology & Engineering
Languages : en
Pages : 609
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Book Description
The present book gathers a large amount of the recent research results on this topic to provide a better understanding of the size effect by giving a quantitative description of the relationship between the properties of engineering concrete-making material (e.g. the nominal strength) and the corresponding structure size. To be precise, this is about to explore the new static and dynamic unified size effect laws for concrete materials, as well as size effect laws for concrete components. Besides presenting clear and accurate descriptions that further deepen our fundamental knowledge, this book provides additionally useful tools for the scientific design of concrete structures in practical engineering applications.
