Flexural ductility of CFRP strengthened concrete beams-experimental investigation

The amount of tension reinforcing steel bars plays a major role in determining the flexural ductility of reinforced concrete beams. The addition of Carbon Fiber Reinforced Polymer (CFRP) composites, which is another form of tension reinforcement. affects the ductility of concrete beams strengthened with CFRP sheets. Several researches have investigated the use of CFRP for increasing the flexural strength of concrete beams. However, the flexural ductility of beams with respect to the amount and yield strength of existing ordinary steel bars has not been investigated in depth. In addition, delamination of CFRP sheets dominates the ultimate mode of failure of flexural members strengthened with CFRP sheets, which limits the ductility of strengthened members. There is a need to investigate the effect of CFRP anchorage system on the overall ductility of strengthened girders. This paper presents the results of an experimental investigation of nine large-scale reinforced concrete beams strengthened with CFRP composite sheets. The main variables are the amount of the existing reinforcing steel bars, yield strength of steel bars. and the type ofCFRP anchorage. The amount (size and type) of the longitudinal CFRP sheets was maintained constant. Test results showed that the lower the amount of existing ordinary steel bars the lower the flexural ductility of the CFRP strengthened beams. Test results have also shown that CFRP anchorage could significantly increase the flexural ductility of CFRP strengthened beams. Such important findings should be reflected on the design equations of CFRP sheets required for strengthening existing reinforced concrete beams to ensure an acceptable level of flexural ductility.