A Rational Approach Towards Modeling of Post-peak Shear Deformation Behavior of Reinforced Concrete Frame Elements Within Finite Element Context PDF Download
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Author: Fawad Muzaffar Shaikh
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Inelastic response of reinforced concrete frame members to combined gravity and lateral loads involves the complex interaction of axial, moment and shear forces and deformations. Whereas there is a considerable body of experimental data and knowledge on the behavior of members that respond predominately in either inelastic shear or moment effects, the behavior of frame elements that are sensitive to combined shear-flexure interaction is less understood. At present, there is little agreement as to how to analyze the behavior of concrete frame elements that experience strength degradation under the combined nonlinear interaction of shear and moment. This study takes a closer look at existing analytical models that have been proposed for simulation of shear effects in frame elements. Experimental behavior of beam-columns as reported by other researchers is catalogued in order to develop an understanding of the actual physical behavior of concrete frame elements. Available experimental data of ductile and non-ductile columns is analyzed to identify key parameters which affect shear deformation behavior of beam-column elements. Bond slip penetration within the plastic hinge regions of the concrete frame elements is found to play a key role in causing shear failure and subsequent post-peak force deformation response of beam-columns. Existing concrete and steel material models are studied and an improved steel material model capable of simulating cyclic hardening, cyclic softening and mean stress relaxation is proposed. The proposed steel model is verified by comparing its simulated response with reported behavior of reinforcing bars. The suitability of the proposed steel material model to simulate random loading history is demonstrated. A numerical framework (i.e. kinematic description, solver routine and control algorithms), capable of simulating large rotation, large deformation, post-peak shear deformation behavior of frame elements is developed. A new analytical model for simulating shear deformation behavior of concrete frame elements subjected to axial, flexural and shear loading is proposed. While the modeling concepts are general, the implementation and verification of the proposed model is limited to two-dimensional response. The proposed element model is based on behavioral effects and parameters that are identified through careful analysis and interpretation of previously published tests of ductile and non-ductile beam-columns. This analytical model is then used along with the proposed numerical framework to simulate local and element level behavior of four non-ductile columns (tested by Sezen and Moehle at U.C. Berkeley), two ductile column stubs (tested by Ichinose, Imai, Okano and Ohashi at Nagoya Institute of Technology) and two beam specimens (tested by Popov, Bertero and Krawinkler at U.C. Berkeley). The proposed element formulation, along with the supporting computational framework (e.g., solution control algorithms), are shown to be capable and robust to simulate the post-peak response of beam-columns due to large flexural and shear deformations. The proposed formulation is shown to be capable of simulating the effect of cumulative flexural deformations, axial load and strength of longitudinal bars on shear strength of beam-columns. Complicated behavioral features, such as the opening of stirrups in non-ductile columns and degradation of aggregate interlock behavior with cycling, are captured in the analysis. The element model was shown to be capable of simulating the correct mode of failure observed in four tests of non-ductile columns. In addition, shear strain, stirrup strain and axial strain of beam-columns were simulated and compared with corresponding available experimental values. The values of the input parameters of the proposed element model were justified and the resulting response was compared with experimental behavior. Generally good agreement was observed between experimental and simulated values.
Author: Fawad Muzaffar Shaikh
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Inelastic response of reinforced concrete frame members to combined gravity and lateral loads involves the complex interaction of axial, moment and shear forces and deformations. Whereas there is a considerable body of experimental data and knowledge on the behavior of members that respond predominately in either inelastic shear or moment effects, the behavior of frame elements that are sensitive to combined shear-flexure interaction is less understood. At present, there is little agreement as to how to analyze the behavior of concrete frame elements that experience strength degradation under the combined nonlinear interaction of shear and moment. This study takes a closer look at existing analytical models that have been proposed for simulation of shear effects in frame elements. Experimental behavior of beam-columns as reported by other researchers is catalogued in order to develop an understanding of the actual physical behavior of concrete frame elements. Available experimental data of ductile and non-ductile columns is analyzed to identify key parameters which affect shear deformation behavior of beam-column elements. Bond slip penetration within the plastic hinge regions of the concrete frame elements is found to play a key role in causing shear failure and subsequent post-peak force deformation response of beam-columns. Existing concrete and steel material models are studied and an improved steel material model capable of simulating cyclic hardening, cyclic softening and mean stress relaxation is proposed. The proposed steel model is verified by comparing its simulated response with reported behavior of reinforcing bars. The suitability of the proposed steel material model to simulate random loading history is demonstrated. A numerical framework (i.e. kinematic description, solver routine and control algorithms), capable of simulating large rotation, large deformation, post-peak shear deformation behavior of frame elements is developed. A new analytical model for simulating shear deformation behavior of concrete frame elements subjected to axial, flexural and shear loading is proposed. While the modeling concepts are general, the implementation and verification of the proposed model is limited to two-dimensional response. The proposed element model is based on behavioral effects and parameters that are identified through careful analysis and interpretation of previously published tests of ductile and non-ductile beam-columns. This analytical model is then used along with the proposed numerical framework to simulate local and element level behavior of four non-ductile columns (tested by Sezen and Moehle at U.C. Berkeley), two ductile column stubs (tested by Ichinose, Imai, Okano and Ohashi at Nagoya Institute of Technology) and two beam specimens (tested by Popov, Bertero and Krawinkler at U.C. Berkeley). The proposed element formulation, along with the supporting computational framework (e.g., solution control algorithms), are shown to be capable and robust to simulate the post-peak response of beam-columns due to large flexural and shear deformations. The proposed formulation is shown to be capable of simulating the effect of cumulative flexural deformations, axial load and strength of longitudinal bars on shear strength of beam-columns. Complicated behavioral features, such as the opening of stirrups in non-ductile columns and degradation of aggregate interlock behavior with cycling, are captured in the analysis. The element model was shown to be capable of simulating the correct mode of failure observed in four tests of non-ductile columns. In addition, shear strain, stirrup strain and axial strain of beam-columns were simulated and compared with corresponding available experimental values. The values of the input parameters of the proposed element model were justified and the resulting response was compared with experimental behavior. Generally good agreement was observed between experimental and simulated values.
Author: Yu Huang
Publisher: Cambridge Scholars Publishing
ISBN: 152755354X
Category : Technology & Engineering
Languages : en
Pages : 305
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Book Description
This book details the theory and applications of finite element (FE) modeling of post-tensioned (PT) concrete structures, and provides the updated MATLAB code (as of 2019). The challenge of modeling PT prestressed concrete structures lies in the treatment of the interface between the concrete and prestressing tendons. Using MATLAB, this study develops an innovative nonlinear FE formulation which incorporates contact techniques and engineering elements to considerably reduce the need of computational power. This FE formulation has the ability to simulate different PT frame systems with fully bonded, fully unbonded or partially bonded tendons, as well as actual sliding behavior and frictional effects in the tendons. It also allows for the accurate simulation of anchor seating loss.
Author: Pui-Lam Ng
Publisher: Open Dissertation Press
ISBN: 9781361429587
Category :
Languages : en
Pages :
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This dissertation, "Constitutive Modelling and Finite Element Analysis of Reinforced Concrete Structures" by Pui-lam, Ng, 吳沛林, 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: Abstract of thesis entitled CONSTITUTIVE MODELLING AND FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE STRUCTURES Submitted by NG Pui Lam for the Degree of Doctor of Philosophy at The University of Hong Kong in September 2007 This thesis is divided into two parts. The first part is devoted to the development of new constitutive models of reinforced concrete. To properly simulate the stress path dependence of concrete, the author devises herein the nonlinear damage model. In this model, the microcracking induced by stressing of concrete is viewed as damage, which is described by two quantifiable damage parameters: the damaged modulus and the residual strain. On the shear behaviour of concrete, it is postulated that the shear stress envelope of concrete is governed by two criteria: the Mohr-Coulomb criterion of maximum shear stress and the non- orthogonal minor crack criterion of maximum shear stress. A stress path dependent shear stress-strain relation of concrete is established. Time dependent analysis of shrinkage and creep effects in concrete structures requires storage of stress histories of finite elements for evaluation of creep. This poses a hindrance to the analysis of large problems. To circumvent the memorisation of stress histories, a new multi-layer visco-elastic concrete creep model is developed. Besides, for structures constructed in stages, re-analysis of the partially completed structure in each stage is necessary in response to changes in structural configurations during construction. Herein, the locked-in strain is introduced to allow analysing altogether the completed and uncompleted portions, thus eliminating the efforts on re-meshing and location matching of element stresses and deformations. The interactions between concrete and reinforcement are simulated in conjunction with the discrete modelling of reinforcing bars. The Goodman interface element is adapted for modelling concrete-to-reinforcement bond with the implementation of nonlinear bond stress-slip relation. Besides, the dowel action for discrete reinforcing bars is modelled based on the beam on elastic foundation theory. The second part of this thesis is on the analysis of reinforced concrete structures. The tension stiffening phenomenon in cracked concrete beams is investigated. From finite element analysis, stress distributions at beam cross-sections are revealed and based on which a tensile stress block is derived. The tensile stress block enables assessment of beam deflections in structural design process without resorting to finite element analysis for each individual beam. Furthermore, the post- peak behaviour of beams and deep beams is analysed. The effects of concrete residual strain, bond slip, and dowel action on beam responses are studied. The finite element programme is applied to the analysis of shear transfer across joints between concrete units, with particular reference to precast segmental post-tensioned bridges. To model the epoxy adhesive between joint surfaces, the epoxy element is developed from the nonlinear linkage element. It is found that with the joint surfaces pressing against each other by prestressing, the shear transfer capacity of flat joints is already sufficient (comparable to intact concrete), and the provision of shear keys at joint surfaces is superfluous from the shear stren
Author: Christian Meyer
Publisher: Springer
ISBN: 3709125243
Category : Technology & Engineering
Languages : en
Pages : 257
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Book Description
A comprehensive review of the material behavior of concrete under dynamic loads, especially impact and impuls, opens the volume. It is followed by a summary of the various analytical tools available to engineers interested in analyzing the nonlinear behavior of reinforced concrete members for dynamic load. These range from relatively simple and practice-oriented push-over analysis to sophisticated layered finite element models. Important design-related topics are discussed, with special emphasis on performance of concrete frames subjected to seismic loads. The significance of modern software systems is recognized by including extensive examples. For readers not current in dynamic analysis methods, an appendix contains a review of the mathematical methods most commonly used for such analysis.
Author: Michael D. Kotsovos
Publisher: CRC Press
ISBN: 1498712312
Category : Technology & Engineering
Languages : en
Pages : 376
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Book Description
A Powerful Tool for the Analysis and Design of Complex Structural ElementsFinite-Element Modelling of Structural Concrete: Short-Term Static and Dynamic Loading Conditions presents a finite-element model of structural concrete under short-term loading, covering the whole range of short-term loading conditions, from static (monotonic and cyclic) to
Author: Comité euro-international du béton
Publisher: Thomas Telford
ISBN: 9780727720863
Category : Technology & Engineering
Languages : en
Pages : 214
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Book Description
This text provides a review of relevant knowledge in the area of constitutive modelling of concrete steel bonds and their interaction. It discusses the problems encountered in assembling the various elements with the purpose of constructing the model of an element made of reinforced concrete. Whether physically or empirically based, very simple or sophisticated, long-established or brand new, the models presented in this book are produced in as rational a framework as possible, and are accompanied by comments on their advantages and limitations.
Author: Yi Wu
Publisher: Open Dissertation Press
ISBN: 9781361428948
Category :
Languages : en
Pages :
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Book Description
This dissertation, "Post-crack and Post-peak Behavior of Reinforced Concrete Members by Nonlinear Finite Element Analysis" by Yi, Wu, 吳奕, 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: Abstract of thesis entitled POST-CRACK AND POST-PEAK BEHAVIOR OF REINFORCED CONCRETE MEMBERS BY NONLINEAR FINITE ELEMENT ANALYSIS Submitted by Wu Yi for the degree of Doctor of Philosophy at the University of Hong Kong in September 2006 This thesis investigates the post-crack and post-peak behavior of reinforced concrete members by using finite element analysis. To achieve this, a finite element code with displacement controlled iterative scheme is developed. The finite element code is able to represent the complete load-deflection curve of reinforced concrete member from the initial loading stage till the post-peak stage. Bond-slip interaction between concrete and longitudinal reinforcement is included. To validate the finite element code, experiments of reinforced concrete members with different longitudinal reinforcement, web reinforcement, concrete strength and axial compression are studied. Case studies show that if the bond-slip is neglected in the finite element analysis, the predicted load-deflection curve and crack pattern will give less accuracy. A study of the mesh size-effect of concrete element shows that the mesh should be fine enough in order to give better prediction. By including the bond element and using proper element size, the results show that the proposed finite element code gives a good description of the behavior of reinforced concrete members, including crack patterns and the load-deflection responses. i By using this finite element code, reinforced concrete beams with different concrete grade, steel ratio are studied to investigate the post-crack behavior of reinforced concrete members. The analysis demonstrates that the predicted load will be under-estimated after the concrete has cracked if the tension-stiffening effect is neglected in the section analysis. Based on the results obtained from the finite element analysis, three new concrete stress distribution blocks are proposed. Compared with the current design codes in which the contribution of cracked concrete in tension is simply neglected or other far more complicated methods proposed for the finite element analysis, the tension-stiffening effect can be taken into account in a simple manner in the proposed models for the section analysis of reinforced concrete beams. Several classic reinforced beams are adopted to validate the proposed models. The results show that the proposed models give a good description of the load-deflection behavior of the reinforced concrete members for cracked concrete. In the investigation of the post-peak behavior of reinforced concrete beams, it is found that beyond the ultimate strength, the strain reversal history of longitudinal reinforcement has significant effects on the load-deflection behavior of the member. The predicted load may be over-estimated for an under-reinforced concrete beam when the strain reversal history of longitudinal reinforcement is neglected. It is therefore suggested that the strain history effect should be included for more accurate prediction of the post-peak load-deflection curves of reinforced concrete members. The variation of curvature along the beam length is also investigated. It is shown that the phenomenon of curvature reversal occurs at the post-peak stage for over- reinforced concrete sections in a simply supported beam that is subjected to concen
Author: Sebastien Bernard
Publisher:
ISBN:
Category : Concrete beams
Languages : en
Pages :
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Book Description
This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a zlocally smearedy approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 2883940851
Category : Technology & Engineering
Languages : en
Pages : 3
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Book Description
Non-linear computer analysis methods have seen remarkable advancement in the last half-century. The state-of-the-art in non-linear finite element analysis of reinforced concrete has progressed to the point where such procedures are close to being practical, every-day tools for design office engineers. Non-linear computer analysis procedures can be used to provide reliable assessments of the strength and integrity of damaged or deteriorated structures, or of structures built to previous codes, standards or practices deemed to be deficient today. They can serve as valuable tools in assessing the expected behaviour from retrofitted structures, or in investigating and rationally selecting amongst various repair alternatives. fib Bulletin 45 provides an overview of current concepts and techniques relating to computer-based finite element modelling of structural concrete. It summarises the basic knowledge required for use of nonlinear analysis methods as applied to practical design, construction and maintenance of concrete structures, and attempts to provide a diverse and balanced portrayal of the current technical knowledge, recognizing that there are often competing and conflicting viewpoints. This report does not give advice on picking one model over another but, rather, provides guidance to designers on how to use existing and future models as tools in design practice, in benchmarking of their models against established and reliable test data and in selecting an appropriate safety factor as well as recognising various pitfalls. fib Bulletin 45 is intended for practicing engineers, and therefore focuses more on practical application and less on the subtleties of constitutive modelling.
Author: L. Javier Malvar
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 60
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Book Description
A smeared crack approach to fracture of concrete in mode I was implemented in the finite element program ADINA. Nonlinear concrete elements with tensile cracking were modified to include tensile strain softening. When an element at an integration point cracks, the stiffness perpendicular to the crack is reduced to zero and the tensile stress across it is set as a function of the crack opening. Equilibrium iterations were implemented to redistribute stress. Two- and three-dimensional models of a single edge notched beam in three-point bending were analyzed and compared to experimental results with good agreement. The analytical representation of mixed mode fracture was also addressed. The mechanisms of shear transfer across a crack were detailed, and the rough crack model, relating shear stress to crack opening, is presented with discussions on orientation of successive crack planes, tensorial invariance, and snap-back phenomena. Problems are identified with modeling bond at the concrete/reinforcement interface and its effect on crack patterns. Keywords: Fracture mechanisms; Crack propagation; Mixed mode; Shear; Bond tension; Softening; Fracture energy; ADINA computer programs. (SDW).
