Effect of size on the failure of FRP strengthened reinforced concrete beams

The bonding of fiber reinforced plastic (FRP) plates is an effective and efficient method to improve the bending capacity of concrete beams. In the literature, various design methodologies have been proposed and several of them have been found to compare well with test data or to provide reasonable lower bounds. However, almost all the experimental data are obtained from laboratory-size specimens that are several times smaller than members in real structures. On close examination, different design methodologies exhibit significantly different trends of load capacity vs member size. With no test results on larger specimens, it is not possible to determine which approach is more appropriate for designing real size members. In this investigation, geometrically similar reinforced concrete beams with steel ratio of 0.01, and depth ranging from 0.2 in to 0.8 in were prepared. Some RC beams were tested as control while others were retrofitted with 2 to 8 layers of Carbon fiber reinforced plastic (CFRP) sheets to achieve the same CFRP/concrete area ratio. All the beams were tested to failure to investigate the variation of failure load with member size. The results of the present investigation are expected to provide useful information for (i) the extrapolation of small specimen results to large members of practical size, and (ii) the checking of theoretical models for design.