Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 6 — Proposal of New Type of Hysteresis Model for Ultimate Behavior

Abstract

This paper describes a new type of hysteresis model applied for seismic response analysis, which provides restoring force characteristics containing various types of hysteresis loops generated by calculating differential equations, based on static breaking tests regarding thick rubber bearings. In order to reduce residual risk, there is increasing necessity to accurately predict seismic response against both design-basis ground motion and ground motion exceeding design-basis. This process of seismic response prediction is called seismic Probabilistic Risk Assessment (PRA). In general, a restoring force of rubber bearing under large deformation due to a major earthquake has strong non-linear characteristics containing the hysteresis loops. To improve the accuracy of seismic response predictions up to the ultimate behavior in PRA, a new hysteresis model to be applicable up to the breaking point in horizontal and vertical directions is proposed by the authors. The features of the proposed hysteresis model are as follows: (1) The hysteresis characteristics obtained by the proposed model have smooth curves as substantive hysteresis loops measured in breaking tests. (2) The various types of hysteresis characteristics can be captured efficiently as initial value problems since the proposed model, consisting of differential equations, directly allows the skeleton function, and unaffected by hysteresis law such as Masing law. This paper indicates applicability of the proposed hysteresis model to seismic response analysis through comparison of results of the static breaking test with results of analytical, and also describes the breaking mode obtained by the seismic response analysis.