Earthquake damage prediction of base-isolated structure includes many fuzzy factors, for example damage grade, intensity and so on, so by use of the fuzzy comprehensive evaluation method to predict the earthquake damage probability of the base-isolated structure should be feasible and effective. The isolated building usually consist of the isolated layer and the upper structure, so the damage grade of the base-isolated structure is divided by the performances of the isolated layer and the supper-structure. And then, the basic frame system of earthquake damage prediction based on fuzzy comprehensive evaluation method is established: the damage influence factors of the earthquake damage prediction for the isolated structure are analyzed, the corresponding hierarchy evaluations system is presented. Grade standard of damage influence factors and the determining method of membership degree for the base-isolated frame structure are given, and then the weight coefficients of the damage influence factors are studied by use of the judgment matrix analysis method, the fuzzy comprehensive evaluation model of earthquake damage prediction is given. Lastly, a numeral example is analyzed, the rationality of the method is proved.
At present, seismic strengthening design reference period of the existing building is usually equal to 50 years in China, sometime this is uneconomic and unreasonable. In this paper, determining principle of seismic strengthening design reference period for the existing building with different importance is presented. The seismic strengthening design level of the existing building is put forward. After the shape factor of intensity probability distribution function is used to represent the seismic hazard characteristic of different areas, the seismic hazard curve formula of design acceleration Amax and earthquake influence coefficient αmax are deduced according to the seismic hazard curve of intensity. The seismic strengthening design ground motion parameter for the existing building with different importance is researched in detail by use of hazard curve formula of seismic ground motion parameter based on seismic hazard characteristic zone. At last, the method and the calculation step are explained by a calculation example. The result shows that for the existing building with different design reference period, using same design parameter is unreasonable in different seismic hazard characteristic zone, and the method is more scientific than the code method.
For the displacement-constraint device with hysteric-friction isolation system, the judgment condition of soft-collision between the isolation layer and displacement-constraint device is put forward, the motion equation of the isolation system in consideration of friction and soft-collision is established, the nonlinear analysis program is worked out, and several kinds of inflection points in the program are given and the corresponding processing method of the inflection points is introduced. The nonlinear response analysis of the isolation system results indicate the displacement-restraint device can ensure the upper structure safety; also can decrease the displacement of the isolated layer.
The hysteric-friction isolation system with elastic-plastic displacement-constraint device is put forward. The action mechanism and restoring force model of the elastic-plastic displacement-constraint device are analyzed. The nonlinear seismic responses of structures supported on Hysteric-friction isolation system with elastic-plastic displacement-constraint device under main shock and aftershock are researched. The results indicate: the displacement-constraint device not only can ensure the upper structure safety, but also can effectively limit the displacement of the isolation layer, meanwhile can supply secondary protection under strong aftershock. The structure of the device is simply, which is convenient for production and installation. Meanwhile because the device is cheap, it can be widely used in isolation building.
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