Itio Hirai

An exact zooming method

Abstract This paper presents an efficient and exact formulation for finding stress concentration factors using a zooming analysis. A favorable characteristics of this method is its ability to perform a zooming analysis with computations taking place only in the zooming area under consideration with no need to treat the region outside the zooming area. At the final zooming step, the flexibility of a limited zooming area is determined for all nodes, including the new nodes created in the zooming processes as well as those of the original system before zooming.

Stable eigensolution of locally modified systems based on the Sturm sequence property

Abstract This paper proposes an analytical procedure for the eigensolution of locally modified systems on the basis of the Sturm sequence property. The fundamental equation is derived retaining the advantages of the Sturm sequence property and is represented in a compact matrix form of the order of the number of modifications. This approach is useful for a modified system with many degrees of freedom, for which relatively few degrees of freedom are involved in the modifications. The accuracy and stability of this method are confirmed using several numerical examples with comparisons to the Householder bisection method.

Sturm sequence recurrence formula for eigensolution of locally modified systems

Abstract This paper proposes a recurrence formula for the fundamental equation derived on the basis of the Sturm sequence property for the eigensolution of locally modified systems. The fundamental equation expressed using a condensed matrix, of order equal of the mrder of the modified part of the system, requires the multiple calculation of a determinant. The number of calculations is equal to the order of the original system. The recurrence formula set forth in this paper avoids multiple evaluations of the determinant. Instead, a particular determinant evaluation is implemented by multiplying the previous determinant by a scalar. The effectiveness of the recurrence formula is confirmed using several numerical examples.

Excitation of Arch and Suspension Bridges by Subwires

A force generation method using a subwire for arch and suspension bridges is proposed. The subwire is connected to the arch or the cable of the bridge through rollers. The uniform force produced by pulling and releasing the pretensioned subwires acts on the bridge as an externalforce. A new device called “the resonance force generator” is also developed to excite the bridges by applying a small force. To verify the proposed concept, a stress ribbon bridge was excited with the resonance force generator.