Flexural strengthening and repairing of heat damaged RC beams using continuous near-surface mounted CFRP ropes

Abstract

CFRP ropes are relatively new and cheap materials that can be used in strengthening and rehabilitating RC elements. This research was designed to investigate the experimental behaviour of heat-damaged and unheated RC beams strengthened and retrofitted using near-surface mounted (NSM) carbon fiber polymer (CFRP) ropes. Ten RC beams were tested under a four-point loading test. Five beams were subjected to 700°C for 3 h and were partially damaged by heat while the other remaining beams were unheated. Several strengthening configurations were adopted where CFRP ropes were continuously anchored along the beam length. The flexural strength of the test specimens was then predicted using the ACI-440 guidelines and compared to the experimental results. Test results showed that the continuous strengthening configuration is considerably efficient in increasing the flexural strength of the RC beams. Adopting two layers of continuous CFRP ropes along the beam length, anchored at the tensile reinforcement level, increased the load capacity and stiffness of the unheated beams by 60% and 78%, respectively. It also restored the load capacity of the heat-damaged beams with an additional 47% in its’ load carrying capacity, but it decreased their peak deflection. Test results showed that the current ACI-440 guidelines that are designed for predicting the flexural strength of RC beams strengthened with NSM bars could be applied to predict the flexural strength of RC beams strengthened with NSM CFRP ropes with a suggested modification factor for the effective strain.