Seismic Analysis Of Reinforced Concrete Frame Structures Subjected To Near-fiedl Earthquake Ground Motions

Among the present research of Wenchuan earthquake, the reinforced concrete frames designed by《Code for seismic design of Industrial and Civil Buildings》TJ11-78(78 edition for short) had more serious damage than those designed by new seismic code. Under this background, the research of this paper involves the following works:1. Ten near-field ground motion records and five far-field ground motion records are selected in this paper. Three frames are designed separately according to 78 edition,《Code for seismic design of buildings》GBJ 11-89(89 edition for short) and《Code for seismic design of buildings》GB 50011-2001(01 edition for short). With the method of increment dynamic analysis, the behaviors of the three frames under the ground motions selected before are studied. And all near-field ground motions have the PGV/PGA>0.2. We found the response of the frames which are subjected to near-field ground motions is larger than those subjected to far-field ground motions. Under the“small earthquakes”, the interstory drift ratio of the three frames is larger than 1/550. The maximum interstory drift ratio is on the first floor. And the responses of the frame which is designed according to 78 edition are larger than the other two frames, but responses of the frame which is designed according to 01 edition are the smallest in these frames. The ten IDA curves can be summarized into the 16%, 50% and 84% fractiles. According to the fractiles, we also can find that the frame designed by 01 edition has the best seismic energy dissipation performance, and the frame designed by 78 edition has the worst seismic energy dissipation performance.2. The basic theory of fragility analysis and its analysis steps are discribed in this paper. The results of IDA are applied to the seismic fragility analysis and the estimation of the limit-states. And then we get fragility curves. The seismic behavior of the three frames can be shown clearly with the fragility curves. The fragility equations of different limit-states are gained through curve fitting by using Matlab Tools.3. Based on the results mentioned above, four codes for seismic design of buildings in China are compared. Conclusion can be made that both 89 edition and 01 edition are better than 78 edition. Because there are still some disadvantages in the 01 edition, it should be improved. A part of these disadvantages are modified in 《Code for seismic design of buildings》GB 50011-2010(10 edition for short), such as seismic design response spectrum.