ANALYTICAL STUDY ON SEISMIC ENERGY BALANCE OF NPP BUILDINGS PART-1 FORMULATION OF ENERGY BALANCE ON SOIL- STRUCTURE INTERACTION SYSTEM

摘要

This paper discusses a method for evaluating the seismic energy balance for nuclear reactor buildings of NPP that have very strong soil-structural interaction. We first conducted intensive nonlinear earthquake response analyses using a simple two-mass sway-rocking model without embedment. Results of these analyses clarified that the total input energy to the soil-structure interaction system can be considered to be constant, and the percentage of effective input energy imposed on the building structure should be seen as an energy distribution problem that depends on the mechanical conditions of the structural stiffness and the soil springs. In order to develop an explicit evaluation method to estimate important structural responses such as ductility factor of walls based only the diagram, we focused on the energy balance between the structure's absorption energy and the effective energy input to the structure by the earthquake. Spectrum characteristics of the earthquake, such as period dependency, can be introduced to the diagram. The so-called energy balance diagram can not only estimate the structural responses but also evaluate the seismic margins based on the relation between the input energy spectrum and the energy absorption capacities due to the structural ductility.