BEHAVIOR OF PLAIN AND STEEL FIBER HIGH STRENGTH REINFORCED CONCRETE COLUMNS CONFINED WITH CFRP

High strength reinforced concrete columns have been increasingly used in structural applications. It is known that high strength reinforced concrete columns exhibit brittle behavior under applied loads. Therefore, steel fibers can be added into the core concrete to improve the ductility and deformability of high strength reinforced concrete columns. In addition, reinforced concrete columns can be wrapped with carbon fiber reinforced polymer (CFRP) materials for strengthening the columns. In this work, experimental and analytical studies on plain and steel fiber reinforced concrete columns and CFRP confined columns have been presented. The experimental strength capacities, load-deflection relations and failure modes of the column specimens have been observed. The effects of the parameters of concrete compressive strength, load eccentricity, steel fibers, and carbon fiber polymer material on the structural behavior of high strength reinforced concrete columns have been examined. It is concluded that the inclusion of steel fibers has considerable effect on column ductility and deformability, but has insignificant effect on column strength capacity. The experimental study exposed that wrapping CFRP material on plain and steel fiber high strength reinforced concrete columns has provided significant improvement on the column strength capacity and confinement. The tested columns have been analyzed with a theoretical method considering the experimental stress-strain relations of CFRP confined concrete; and the analysis shows good agreement with the experimental results.