Seismic Analysis Of Reinforced Concrete Frame Structures Subjected To Near-field And Far-feild Earthquake Ground Motions

Several famous big earthquakes happened in recent years, there are common features, which is near- field earthquake and its damage is very serious. Near- field earthquakes have obvious pulse effect, comparing with far-field earthquakes. Different kinds of pulse will cause different structural response. Near- field earthquakes not only cause serious damage, but also have wide influence. For some large and medium-sized cities near fault, once an earthquake happen, the casualties and economic damage will be immeasurable. Studying responses of structure under different seismic characteristics is of great importance, for structure design, evaluation and maintenance of existing buildings.In this paper, first of all, main characteristics of near-field ground motions are introduced, then near- field ground motions with fling step effects are emphasized. Compare code of China, the United States and Japan about the near- field earthquake protection, then introduce the development of code of C hina and their deficiencies are summarized.Secondly, the paper has selected near-field ground motions with forward directivity effects, near-field ground motions with fling step effects and far- field ground motions as inputs, made dynamic elastic-plastic analysis on three RC frame structures with different stories. Some seismic performance indexes, such as inter-story drift, base shear, damage of concrete and plastic strain of steel were proposed to compare and contrast respective responses.Results illustrate that, when PGA of each records are equal, inter-story drift demand is mostly bigger in low story under near-field ground motions, while mostly bigger in medium or upper stories under far- field ground motions, and drift demand is biggest under near-field ground motions with fling step effects. For 6-story and 10-story frame structures, damage of column is more serious under near- field ground motions with forward directivity effects, while damage of beam is more serious under near- field ground motions with fling step effects. It shows that responses of RC frame structure under different ground motions are different with each other, and the impact of these features should be paid attention to during the design review.Finally, take 6-story frame structure as an example to calculate and analysis, based on the displacement or damage, and discuss the application of performance-based method in near- field seismic design.