B3 有効質量を用いた拘束のない構造物のモード選定

Abstract

The purpose of this paper is to show that the effective mass is a useful indication also in identifying dominant mode of unconstrained structures. Effective mass concept works well for structures with constraint, but it does not work for unconstrained structures with rigid-body modes. This is the reason all the effective masses for elastic modes are zero. A way to use the effective mass for dominant mode identification of unconstrained structures is to put zeros into elements in rigid-body modes. Although the effective mass takes different values by which element is replaced with zero and by zeroing rate, modes with large effective mass are dominant mode. However, we cannot necessarily judge that modes with small effective mass are not dominant for a zeroing rate. It is found that it is effective to select a zeroing node that modes are asymmetry with respect to the node in identifying dominant modes. A numerical example is given to show that the proposed method is effective for dominant mode identification of unconstrained structures.