WIT Press

Development Of Interaction Diagrams For RC Sections Confined With CFRP Composites


Free (open access)

Paper DOI






Page Range

385 - 396




424 kb


P. Christou, A. Michael & Z. Neofytou


The interaction diagram is a surface which defines the maximum capacity of compression members that are subjected to axial force and bending moments. As a result, these diagrams provide the engineers with an additional tool for the design of such members. When the compression members are confined with FRP their capacity increases, however in many cases the increase in capacity is normally neglected which sometimes can lead to very conservative designs. This work includes the development of interaction diagrams for circular compression members confined with CFRP using the fiber model. The longitudinal reinforcement is considered to be symmetric whereas the confinement can vary. The method presented herein defines the location of the neutral axis and based on that calculates the axial force and bending moment. A comparison of the unconfined to the confined section shows a considerable difference in the interaction diagram plot in the compression controlled region. Keywords: interaction diagrams, confinement, section equilibrium, RC section strength. 1 Introduction The analysis of concrete columns using an analytical solution is not trivial. As a result the analysis of columns is basically reduced to the development of the interaction diagram and the plot of the load condition in order to define failure or not for the section. Normally the confinement for compression reinforced concrete sections is provided either by ties or spirals. However, other methods and materials are used in the later years which can provide increased confinement and thus satisfy the requirement for increased ductility. The column wrapping with CFRP composites is a popular alternative for improving the


interaction diagrams, confinement, section equilibrium, RC section strength