Fire Resistance Performance of the Bond-Type Anchorage System for CFRP Cables

This study conducted fire resistance tests on bond-type anchorage systems using ultrahigh-performance concrete (UHPC) as a bonding medium for two types of carbon fiber–reinforced polymer (CFRP) cables. The study assessed the impact of the initial pullout load, effective bond length, and temperature–load path on the fire resistance of the CFRP cable–UHPC interface. Based on maximum slippage and the rate of slippage, the criteria for failure were established along with a practical model to predict the fire resistance duration for this interface under fire conditions. Subsequently, the fire resistance of the CFRP cable–UHPC interface was compared with that of the CFRP cable alone to evaluate the performance of the bond-type anchorage system. The results indicated that slip failure at the CFRP cable–UHPC interface was the predominant mode of failure across all tested anchorages. The fire resistance duration and the failure temperature of the CFRP cable–UHPC interface ranged from 8.1 to 40.7 min and 136°C to 251°C, respectively, as the initial pullout load ratio decreased from 0.6 to 0.2. The fire resistance performance of the CFRP strand cable–UHPC interface was superior to that of the ribbed CFRP cable–UHPC interface when the initial pullout load ratio varied between 0.4 and 0.6. However, the opposite result was observed when the initial pullout load ratio was 0.2. Introducing an initial pullout load before heating exacerbated the reduction in the load-bearing capacity of the CFRP cable–UHPC interface under fire conditions. The performance of the bond-type anchorage system under fire depended more on the CFRP cable than on the CFRP cable–UHPC interface when the pre-tension load ratio of the cable exceeded 0.15.