RESEARCH ON THE BOND BEHAVIOR OF CORRODED REBAR AND CONCRETE UNDER HEATING AND CONSTANT LOADING CONDITION

High temperature and load level affect the durability and load-bearing capacity of reinforced concrete (RC) structures, but the bond performance tests are mostly steady-state pull-out tests, and the response of structures to fire plus loading excitation is mostly transient performance. The existing tests results overestimate the structural performance. This study conducted the bond behavior test under transient conditions to compare the differences in bond performance under different load conditions by designing 108 specimens. The test results show that the bond failure of the transient pullout specimen is more sudden than that of the steady one, and that the maximum crack width can reach 2.93 mm. For specimens with the same failure temperature and failure load, the energy dissipation of transient specimens is 1.2 times that of steady-state specimens. When the load ratio is 20%, the steel bar fracture occurs in the specimen, when the load ratio is 40%, the bond failure temperature is 320 ℃, and when the load ratio is 60%, the failure temperature is 180 ℃. Based on the test data, the modified coefficient of bond performance is obtained, and the failure slip-location model is established. Finally, the bending failure time and bonding failure time is compared, and the calculation formulae of bending failure time for corroded beams under fire are developed. The study gives the theoretical basis for the collapse time prediction of corroded structures under fire.