Direct Displacement-based Seismic Design Method Of High-rise Buildings

The Performance/Displacement-based Seismic Design method is briefly introduced. The basic methods and corresponding design procedures of Displacement-based Seismic Design are emphasized. Against to Direct Displacement-based Seismic Design (DDBSD), this paper, based on previous research achievements, manages to solve two problems, and it will make this new design method more perfect.(1) How to consider higher mode effects. First, the natural periods and corresponding modes of structure are obtained by free vibration analysis. Based on the periods, the equivalent displacement of single-degree-of-freedom system for each mode is deduced by displacement response spectra, and the structural lateral elastic displacement of each mode could be determined by "Equivalence Principle". So the structural lateral elastic displacement can be obtained by SRSS rule. Then, based on the story drift ratio limits, the structural target lateral displacement of each mode could be determined, and the shear in each story is obtained by SRSS rule too.(2) How to make the anticipating displacement and the actual displacement more coincidental. Some problems in Pushover analysis is discussed, it illustrates that the structural scheme is very important in Direct Displacement-based Seismic Design. The roof's target displacement of RC frames is deduced by its lateral displacement mode, the relationship between roof's target displacement and equivalent displacement is determined. Based on displacement response spectra, the equivalent period for each performance level could be deduced by equivalent displacement. Then, the degradation of structural stiffness is presented by pushover curve, and the relationship among natural periods of each performance level is determined. According to the relationship between natural periods and corresponding equivalent period, the optimal structural scheme is chosen.The paper illustrates the application of the proposed procedures with examples and attempts to prove their feasibility by pushover analysis. It provides a valuable thought to DDBSD method of high-rise buildings.