ANALYSIS ON COLLAPSE RESISTANT CAPABILITY OF REINFORCED CONCRETE FRAME STRUCTURE UNDER WENCHAN EARTHQUAKE

By seismic hazard investigation and numerical simulation,the collapse resistant capability of a reinforced concrete frame structure designed according to active seismic design code is studied.The seismic damage statistics indicate that RC frame structures designed to comply with seismic fortification intensity of 7 commence to collapse(account for 1%~2%) when earthquake intensity reach to 9 or peak ground acceleration(PGA) exceeds 400 gal.Large numbers of RC frame structures(over 60%) will collapse when the earthquake intensity reach to 11 or PGA greater than 800 gal.The further incremental dynamic analysis under Wenchuan earthquake waves shows that frame structure designed according to seismic intensity 7 can overcome PGA from 300gal to 500gal(approach to seismic intensity 9) without collapse,and it can overcome PGA from 400gal to 600gal(nearly seismic intensity 10) while designed according to seismic intensity of 8.As a result,it is found that the overstrength coefficient of a RC frame structure strictly conform to the current seismic code is larger than 2 usually.