Yoji Mizuta

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.

A study on improving the design of hybrid stress-ribbon bridges and their aerodynamic stability

Abstract Preliminary designs were made for the proposals for the ‘stress-ribbon cable-stayed suspension’ and the ‘stress-ribbon suspension’ bridges with an open-grating deck plate for pedestrian use. The findings of this study revealed the followings: That the horizontal component of tensile force in the cables can be reduced up to 1/23 of the conventional concrete stress-ribbon bridges; the maximum deflection of the girder under asymmetrical live load can be well controlled by installing central clamps; the critical flutter speed is sufficiently high; and that vortex-induced oscillation does not occur. The application of the proposals for hybrid structures to vehicle bridges was also examined.

Prediction of vortex-induced oscillations of a bridge girder with span-wise varying geometry

Abstract There are cases where it is difficult to predict the amplitude of vortex-induced oscillation accurately by using a single wind tunnel 2D model. An example of them is proposed sine-curved hybrid cable-stayed bridge girder with span-wise varying geometry discussed in this study. First, the aerodynamic damping force was measured for five 2D models in a wind tunnel. Next, a linearized method for 3D numerical analysis was prepared and then applied to predict the amplitude of the oscillation for this bridge. Since one of the triangular fairings examined was found to be effective in suppressing the oscillation, it was decided that the bridge girder with this fairing should be included in its detailed design. Also, the precision of the solution obtained by the numerical analysis was found to be sufficiently high for the case where much smaller number of 2D models was used.

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.