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Keywords: reinforced concrete column, transverse reinforcement, confinement, negative geometric stiffness, buckling of concrete struts, spacing of transverse reinforcement, mechanical ratio of transverse reinforcement, tensile yielding of transverse reinforcement, degradation of Young's modulus of concrete.

Summary

In a previous work by the authors investigating RC column confinement, a truss model was used, with bars obeying nonlinear uniaxial stress-strain laws of concrete or steel. For nonlinear static analysis of a RC column, within each loading increment, equilibrium conditions were written with respect to the deformed structure, so that to take into account geometric nonlinearities. Numerical experiments revealed two structural instability modes: a local one due to spalling and a global one due to buckling of internal longitudinal concrete struts. In the present paper, based on above global instability mode, the conditions, under which buckling of internal longitudinal concrete struts occurs, are investigated, and the required mechanical ratio of transverse reinforcement is determined, which prevents this buckling of concrete. This is achieved by writing two simple equations: first, an equilibrium condition, along direction of transverse reinforcement, which is in tensile yielding. Then, an inequality is written, that positive elastic stiffness minus negative geometric stiffness of an internal longitudinal concrete strut must be greater than zero. The mechanical ratio of transverse reinforcement must be quite large, so that to counterpart the Young's modulus degradation of concrete. The proposed method is applied to a typical RC column, in potential plastic hinge regions at ends of column, as well as in "elastic" middle part of column and is found in close approximation with relevant UBC recommendations, which are based on test data.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 108 PROCEEDINGS OF THE FIFTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: J. Kruis, Y. Tsompanakis and B.H.V. Topping Paper 20 Reinforced Concrete Column Confinement interpreted as a Structural Stability Effect of Concrete P.G. Papadopoulos and D. Plasatis Department of Civil Engineering, Aristotle University of Thessaloniki, Greece doi:10.4203/ccp.108.20 purchase the full-text of this paper Full Bibliographic Reference for this paper P.G. Papadopoulos, D. Plasatis, "Reinforced Concrete Column Confinement interpreted as a Structural Stability Effect of Concrete", in J. Kruis, Y. Tsompanakis, B.H.V. Topping, (Editors), "Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 20, 2015. doi:10.4203/ccp.108.20 Keywords: reinforced concrete column, transverse reinforcement, confinement, negative geometric stiffness, buckling of concrete struts, spacing of transverse reinforcement, mechanical ratio of transverse reinforcement, tensile yielding of transverse reinforcement, degradation of Young's modulus of concrete. Summary In a previous work by the authors investigating RC column confinement, a truss model was used, with bars obeying nonlinear uniaxial stress-strain laws of concrete or steel. For nonlinear static analysis of a RC column, within each loading increment, equilibrium conditions were written with respect to the deformed structure, so that to take into account geometric nonlinearities. Numerical experiments revealed two structural instability modes: a local one due to spalling and a global one due to buckling of internal longitudinal concrete struts. In the present paper, based on above global instability mode, the conditions, under which buckling of internal longitudinal concrete struts occurs, are investigated, and the required mechanical ratio of transverse reinforcement is determined, which prevents this buckling of concrete. This is achieved by writing two simple equations: first, an equilibrium condition, along direction of transverse reinforcement, which is in tensile yielding. Then, an inequality is written, that positive elastic stiffness minus negative geometric stiffness of an internal longitudinal concrete strut must be greater than zero. The mechanical ratio of transverse reinforcement must be quite large, so that to counterpart the Young's modulus degradation of concrete. The proposed method is applied to a typical RC column, in potential plastic hinge regions at ends of column, as well as in "elastic" middle part of column and is found in close approximation with relevant UBC recommendations, which are based on test data. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £75 +P&P)
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