Seismic Retrofit of R/C T-Beams with Steel Fiber Polymers under Cyclic Loading Conditions

This paper presents results of an experimental study on seismic response of reinforced concrete (RC) T-beams with shear deficiencies strengthened with externally bonded steel fiber reinforced polymer (SFRP) strips. Seven cantilever RC beams were strengthened with externally bonded uniaxial SFRP strips in a U-shape configuration and were tested under cyclic loading conditions. The two main variables examined were the strip spacing and the use of anchoring system. Among the investigated anchoring systems, one was patented, and it is studied in the present manuscript. The examination of the results leads to the conclusion that the anchoring system has a significantly more pronounced effect on the performance of the beams and the mode of failure than the type or spacing of the strips. Furthermore, SFRP strips seem to have a great potential to be used for shear strengthening, especially since the use of mechanical anchoring systems drastically improves their performance. On the contrary, the lack of mechanical anchoring results in premature delamination of the strengthening system, and thus an undesirable SFRP material performance.