A RESTORING FORCE MODEL OF CORRODED REINFORCED CONCRETE FRAME BEAMS IN OFFSHORE ATMOSPHERIC ENVIRONMENT

To study the seismic behavior of corroded Reinforced Concrete (RC) frame beams in offshore atmosphere, the hysteretic behavior of 8 RC frame beams were investigated experimentally, which have been damaged by the salt spray corrosion cycles under low cyclic reversed loading. Based on the test results, a trilinear skeleton curve model with negative stiffness of frame beams was established. According to the characteristic parameters of the intact member's restoring force model, the formula of the characteristic points of the skeleton curve of RC frame beams with corrosion was obtained, which considered the corrosion rate and stirrup ratio. The cyclic degradation indexes of RC frame beams based on hysteresis energy dissipation was obtained through regressive analysis. Subsequently, the restoring force model of corroded RC frame beams was established, which considered the pinch-in effect, strength degradation, unloading stiffness degradation, hardening stiffness degradation and reloading stiffness accelerates degradation. The results show that the seismic performance of RC frame beams deteriorates obviously with the increase of corrosion degree, and the hysteretic energy consumption decreases gradually. The influence of stirrup ratio on the restoring force of RC frame beams is similar to the un-corroded frame beams. The restoring force model can describe the hysteretic behavior of corroded RC frame beams well. The study results will shed light on the theoretical research about the elastic-plastic dynamic analysis of RC structures.