STUDY ON SEISMIC PERFORMANCE OF MULTI-AGE RC FRAME STRUCTURES UNDER CHLORIDE ION ATTACK

Chloride ion ingressing into concrete will cause durability problems and eventually lead to the degradation of structural seismic performance within time. At material level, this paper simulates the influence of chloride ion erosion on the properties of RC frame structure materials by considering the weakening of area of reinforcement, the softening of the cover concrete, and the ultimate strain reduction of confined concrete, etc., which was verified by relevant experiment data. At structure level, based on the mechanical properties degradation model of above materials and fiber, the pushover analysis of RC frames of three, six and eight layers (0, 30, 50 and 70 years) and the dynamic time history analysis of the six-layer multi-age frame were carried out, and then the degradation of bearing and deformation capacity and the variation of interstory drift ratio are studied. The results show that: after structural corrosion, with the increasing of service age, the yield displacement, ultimate displacement, failure displacement, ductility and softening stiffness are gradually reduced, and the yield PGA and collapsed PGA of the structure are also decreasing, while the maximum interstory drift ratio of the structure is increasing. Moreover, the interstory drift ratio of the structure under strong earthquakes is more sensitive to the service age than moderate earthquake.