Collaspse Comparison Of RC Frames Designed In Different Periods During Strong Earthquake Motion

Investigations into the earthquakes'damages indicate that the casualties and losses are mainly resulted from structural collapse. In the present paper, the collapse of RC frame structures is investigated to provide suggestion for reinforcement of aged RC frames and revision of the current code (GB50011-2001). The main contributions are described in the following aspects:First, the national codes for seismic design (TJ 11-78, GBJ 11-89 and GB50011-2001) are compared. According to these codes, a typical RC frame is designed. The result shows that, the shear and compression capacity of the frame components designed following GBJ 11-89 is much higher than those of the frame components designed following TJ 11-78, and the capacity and stiffness of the frame components designed following GB50011-2001 are much higher than those of the frame components designed following GBJ 11-89.Second, a new revised hysteretic model is used in the program. Pre-processing and post-processing are also added to the program. The collapse of frames designed following different codes during the motion of ElCentro wave, Taft wave and Ninghe wave is simulated. It is concluded as follows: (1) Aseismic safety of frames designed following TJ 11-78 is obviously insufficient, they collapse easily under severe earthquakes, which starts from brittle failure. In strong earthquake areas, the frames built before 1990 should be reinforced. Their shear and compression capacity should be improved to prevent brittle failure. (2) Frames designed following GBJ 11-89 and GB50011-2001 have some capacity to resist strong earthquake motion. The stiffness of the frame designed following GBJ 11-89 is more reasonable than that of the frame designed following GB50011-2001. It is suggested that for some new designed frames, the limitation on the interstory drift should be released to some extent.Finally, to reduce the casualties caused by collapse, some measures for forming reasonable collapse mechanisms and increasing the time that structures keep stable during strong earthquakes are discussed.