Research And Application Of Direct Displacement-based Seismic Design Theory For Large Thermal Power Plant Frame Structure

As the development trend of modern seismic design, performance-based seismic design(PBSD), an emerging and advanced concept for seismic design of structure, has many characteristics, such as flexibility, suitability and Pertinence. Because of its such advantages that the performance level is more straight forward and the method is easy to use, direct displacement-based seismic design, one of the methods of the performance-based seismic design theory, gets lots of researchers'attention.This paper reviews the analysis of the domestic and foreign literature, and the development process of structure seismic design theory, and comprehensively expounds the direct displacement-based seismic design basic theories. By using a kind method of the direct displacement-based seismic design theory, a four floor frame structure is designed according with different performance levels. In this design process, the RC frames'seismic performance is divided into three levels:serviceability, life-safety, and collapse protection, and this paper quantifies the three levels by storey drift ratios. Applying the inverted triangular distribution of lateral force to the cantilever column of identical section, and the displaced shape of the column is regarded as the initial mode of lateral displacement. The multi-degree-of-freedom system is transformed into an effective single-degree-of-freedom system, and the corresponding equivalent parameters are derived. The target displacement is determined according to the corresponding performance level, and the lateral displacement curve is modified by the assumed lateral displacement mode. The equivalent period is determined by using the elastic displacement response spectra, and then the structural members are designed. And the results calculated are verified by non-linear static analysis method. The influence of displacement model on direct displacement-based seismic design was also studied.From the design example we found that the structure designed with direct displacement-based seismic can control the displacement well because displacement can reflect the performance of the structure better than that of strength. So index of the different performance levels expressed by the inner-story drift ratio can availably control the seismic behavior of reinforced concrete frame structure under different earthquake levels, which is helpful to the structure designer. Index of the different performance levels expressed by the inter-story drift ratio can availably control the seismic behavior of reinforced concrete frame structure under different earthquake level, which is helpful to the structure designer. However, when the earthquake magnitude increased, sometimes the sections of beam and column should be increased. From the analysis through different displacement model we found that different displacement model directly influenced the outcome of calculated results based on direct displacement-based seismic design and we should do more research on the displacement model of the structure.