免震積層ゴムの横剛性と座屈強度

概要

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The lateral stiffness of a multilayer elastomeric bearing under the vertical load is defined by the ratio of the lateral force to the relative displacement between the both end plates in the lateral direction. The buckling load is determined by the limiting condition that the lateral stiffness happens to be lost.Several analytical studies have been presented up to date on the lateral stiffness by simplifying this laminated structure of steel plates and rubber layers, as a circular composite cylinder having homogeneous material properties.In this paper, we derived a finite difference equation for the lateral displacement of each steel plate by utilyzing the bending and the shearing stiffness coefficients of a thin rubber layer, and obtained an explicit formula for the lateral stiffness of the elastomeric bearing, from which the buckling strength was determined. Then, we gave further an exact formula for the bending stiffness coefficient of the rubber layer sandwiched by two rigid plates and verified it experimentally.It is shown that the buckling load calculated by this theory becomes considerably lower than that predicted by the previous theories. Additionally, the shearing stress distribution at the bonded surface between the rubber layer and the steel plate is discussed, providing an approximate formula for the maximum shearing stress.
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