Analyze About The Response Of Multi-storey Reinforced Concrete Structure Under Near-fault Earthquake

This paper collects 63 near-fault earthquake pulse-typed records, which are divided into hard soil and soft soil by site-type, and three groups as M <6.5, 6.5≤M <7, M≥7 by earthquake magnitude. The acceleration response spectrums of the records are calculated, the results show that the greater the magnitude is and the softer the site is, the response spectrum has longer acceleration sensitive range and velocity sensitive range; the acceleration value of the response spectrum is greater at middle and long period. Then compared the design spectrums with the near-fault acceleration response spectrums calculated, the results show that the design spectrums are less than near-fault acceleration spectrums in the acceleration sensitive range and velocity sensitive range, it is insecurity that design spectrums were used for design in near-fault locations.According to different site-type and magnitude, the paper calculates responses of 15-story and 5-story reinforced concrete frame structure respectively under near-fault earthquake motions. The softer the site-type is and the greater the earthquake magnitude is, the greater the responses of 15-story framework are, because the first vibration mode of 15- story framework has a relatively long first natural vibration period, and that if the magnitude is greater and the site is softer, acceleration value correspond to the response spectrum is greater at middle and long period, so the structure suffer greater earthquake force and the structural responses are greater. Influence of magnitude for the responses of 5-story framework is uncertainly, the responses of 5-story framework are greater on condition of soft soil than on condition of hard soil.The paper compares the seismic decrease effect of eight-story reinforced concrete base-isolated structure under the far field earthquake with under near-fault earthquake. The results show that the seismic decrease effect decreases under near-fault ground motion with long-period velocity pulse. Then the base-isolated structure is simplified to single degree of freedom ideally, and the paper analyzes the responses of superstructure when the natural period and bearing damping ratio changed.