Anchored CFRP ropes for flexural capacity recovering of thermally damaged RC one-way slabs

Abstract

The effectiveness of utilizing near surface mounted (NSM) ropes of carbon fiber reinforced polymers (CFRP) in restoring the mechanical performance of heat-damaged RC slabs were studied using anchored and un-anchored techniques. The CFRP anchorage is supposed to increase the flexural behavior of the RC one-way slabs under investigation. To achieve this purpose, a total of (24) RC 1100 mm (long) × 500 mm (wide) slabs were devised. The experimental slabs were made in three heights; 60 mm, 80 mm, and 100 mm. Using an electric furnace for two hours each time, six of the slab were exposed to 200 °C, another six slabs were exposed to 400 °C, and the third group of six slabs was exposed to 600 °C, while the remaining six slabs were at room temperature. Twelve slabs were reinforced, in tension, with NSM-anchored ropes of CFRP. A test setup for 4-point loading was used to examine the slabs’ mechanical performance, while NSM CFRP ropes’ strain was measured. Also, the cracking patterns and failure modes were observed and documented. The slabs, with/without strengthening and damaged-by-heat/retrofitted, improved their toughness and load capacity up to 189% and 225%, respectively. In contrast, the slabs encountered a degradation in their displacement ductility with respect to the control slabs up to 2%, with the toughness ductility being increased up to 186% based on the slab’s rigidity and the exposed temperature. The present research demonstrated that the anchored NSM CFRP ropes to rehabilitate damaged-by-heat slabs was efficient in regaining the flexural behavior; the monitored behaviors indicated that. Lastly, it was observed that the improvement in the slabs was controlled by the transverse end-anchoring’s effectiveness, which permitted the prime ropes of CFRP to contribute more to the flexural performance without the possibility of the occurrence of un-expected de-bonding caused by cracking, even when the slabs reached their capacity. Based on the research findings, anchoring the utilized CFRP ropes and predicting its capacity using the proposed guidelines is recommended.