The
strengthening of RC beams with CFRP laminates has been extensively studied, and
design recommendations have been published in many countries (ACI 440,
CNR-DT200, CEB-FIP 01, etc.). Few data are available for Near Surface Mounted
(NSM) FRP strengthening techniques or for concrete beams that are repaired
first using cementitious mortars and then reinforced with FRP materials. A
specific experimental campaign, with more than 200 beams, has been carried out
to investigate many factors that can affect design in the common practice, such
as concrete compressive strength, concrete fracture energy, FRP reinforcement
ratio, FRP type, repair technique (plating, NSM, new concrete cover), fatigue,
and aggressive environment. Tests on 4-point bending showed the good
performance of FRP strengthening, as the minimum increment in peak bending load
was 110 percent, and the maximum was 430 percent. The influence of fatigue, if
the peak cyclic load is kept below 30 percent of ultimate quasi-static load, is
negligible in the overall performance. Saltwater contact and temperature
variation have a more significant effect in reducing ultimate capacity,
especially because the internal steel reinforcement corrodes, and the interface
adhesion strength degrades. The effect of concrete cover replacement was also
investigated—the influence of high strength shrinkage-compensated cementitious
mortar is negligible because the interface adhesion with the original concrete
is similar to the epoxyconcrete adhesion. Moreover, the internal steel
reinforcement is protected against aggressive environments.