CFRP ropes for retrofitting heat-damaged concrete beams

Abstract

The contribution of fiber reinforced polymer (CFRP) ropes for recovering mechanical performance of post-heated reinforced concrete beams is experimentally investigated. The ropes are implemented at variable profiles (parabolic, trapezoidal, and straight) within the side cover (NSM) or through the core of concrete beams (post-heated for 3 h to 400 and 500 °C). The mechanical response was evaluated under the effect of four-point loading with deflection and elongation measurements (in CFRP ropes) acquired versus loading up till failure. Meanwhile, load cracking formation and propagation until failure were observed and documented. Post-heating performance was also evaluated in terms of cracking severity and degradation in mechanical properties of concrete and reinforcing steel. The repaired beams recovered partially to fully their original load capacity while lost modest portion of their rotational ductility (at 17–37%). The best mechanical performance is attained when using the parabolic followed by the trapezoidal profiles. Higher damage extent had a more negative impact upon repair efficiency, evaluated by the different performance indicators of the study. Except that repaired with a straight profile, all beams showed sudden shear failure upon the rupture of the CFRP ropes near their anchorage ends. • It is advisable to strengthen concrete beams with SNSM CFRP ropes at variable profiles. • The best repair benefit was attained using a parabolic profile of SNSM CFRP ropes. • Anchorage of the CFRP ropes at their ends led to a significant improvement in repair efficiency. • Use of CFRP ropes at variable profiles altered the failure modes for the heat-damaged beams.