Study On Performance Based Rigid-Plastic Seismic Design Method To Reinforced Concrete Structures Under Strong Earthquake

The practical experience of relieving earthquake disaster is accumulated during struggling against the earthquake which is one of disasters threat to human. With scientific and technological progressing, the seismic causes and its damage phenomenon is constantly specialized. Especially, with emergence of many seismic theories and methods, structures designed based on these theories void or relieve the earthquake disasters during the different phase of 20th century. At the end of the 20th century, the spectrum and the elstoplastic time history analysis are used widely and the performance (displacement)based seismic deign (PBSD) theory is proposed in international seismic field. The displacement and plastic energy dissipation are considered two important influence factors of seismic performance in the theory. The PBSD conception is embodied to some extent in the Chinese code for seismic design of buildings(GB50011-2001) which has three levels of fortification and two phases of designing estimates and adopts time-history analysis and push-over analysis, but this doesn't fully implement the structural performance levels and damage behaviors which are expected by PBSD at various seismic fortification levels in future earthquake. Now seismic design are adjusting to international developing trend and developing PBSD suitable to Chinese condition.Current Status of the Study is expatiated and the feature of PBSD is analyzed and the research trend is represented, and on the basis of character of ductility R.C. structural load-displacement curve, using rigid-plastic model, the performance rigid-plastic seismic design for R.C. structures under strong earthquake theory outline is presented and main findings listed as follow:1. Base on the docility structural mechanism of energy dissipation and displacement control principles of PBSD, a new method of rigid-plastic available to RC frame is developed and a new approach of the performance based design is provided. The design proceeds by two steps. First step is controlling suitable collapse mechanism and transforming it into single degree of system using virtual work principle. Second one is determining seismic demand by rigid–plastic spectrum. The method has advantages of clear notion, simple calculation and reliable accuracy.2. Rigid-plastic displacement spectrum in which the yield acceleration was considered as the parameter is produced, by means of nonlinear time history analysis using the program developed employing Matlab. Then the envelope of the rigid-plastic response spectrums, which are reproduced by sufficient number of accelerograms such as El Centro record, Taft record and Lan-zhou can be used to estimate the seismic demand after adjusting to specified peak ground acceleration.3. Based on the plastic deformation characters of shear wall, which is transformed into single degree of system respectively using virtual work principle. Effects of shearing deformation on the plastic deformation of shear wall are analyzed. RC shear wall can be designed following the same procedure as the plan frame using modified response spectrum through a suitable parameter. The comparison of result with ones by using non-linear time-history analysis shows good agreement, and the difference is less than 10%.4. Based on the response character and energye dissipational mechanism, the mechanical behavior of sliding seismic isolated structure is descried by a rigid-perfectly pastic model. Seismic demands of sliding seismic isolated bearing and upper structure are determined by RPSD method, and the sliding seismic isolated structure is designed. The results of example indcats that the adopted model is approate and the results is accrtate.5. A PBSD rigid-plastic scheme to estimate seismic demands for RC frame structures subjected to bi-directional ground motion is proposed. The inelastic interaction of the biaxial member end moments at the plastic hinges is considered. By using the yield condition in generalized stress space and associated flow rule, the Rigid-Plastic constitutive relation is deduced.