The Load-Carrying Capacity of Reinforced Concrete Beams Strengthened with Carbon Fibre Composite in the Tension Zone Subjected to Temporary or Sustained Loading

Abstract

The article presents the results of the research carried out on the reinforced concrete beams under bending strengthened in the tensile zone with carbon fibre composite. The beams under bending were subjected to short-term and sustained static loading. The duration of sustained loading was 400 and 863 days. A total of four series of beams with different reinforcement ratio and loading duration were tested. Experimental research showed that sustained loading reduces the load-carrying capacity of the beams. Prior to long-term testing of the beams, the load-carrying capacity of control beams subjected to short-term static loading was measured. The decrease of the strength of the beams was caused by a long-term creep effect of concrete in the compression zone as well as plastic shear deformations in the bond of concrete and carbon fibre. To calculate the bending capacity, the built-up bar theory enabling estimation of short and long-term deformation capacity in the bond of concrete and carbon fibre was applied.