SHEAR STRENGTHS OF RC BEAMS RETROFITTED WITH CONTINUOUS FIBER SHEET

Abstract

The seismic retrofitting technique using continuous fiber sheets made of carbon, aramid or glass fibers has been applied to beams of existing reinforced concrete buildings as well as the columns. In order to improve shear capacity, the beams should be confined by wrapping in the fiber sheets. Beams, however, are generally cast with slabs, making wrapping impossible. One of the possible solutions is anchoring of the sheets using bolts and steel plates under the slab (semi-closed type strengthening). Behaviors of the semi-closed type beams, however, are not identical to those of the closed type, in which the beams are completely encased in the sheets. In this study, upper bound theorem is employed to estimate the shear strengths of the beams. Results of the analysis show a trend that strain ε_<Fc>, of the continuous fiber sheet at ultimate stage is reduced as the sheet stiffness p_<wF>E_F increases. Influences of lateral steel reinforcement ratio, geometry of the beam and concrete strength are also discussed.