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CivilComp Proceedings
ISSN 17593433 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 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", CivilComp 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 stressstrain 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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