Hideto Kanno

Magnetic Rubber Having Magnetic Clusters Composed of Metal Particles

For the purpose of assembling metal particles on a nano- or microscale, in a previous investigation the authors had succeeded in extracting magnetic clusters from an intelligent fluid responsive to a magnetic field. The clusters are shaped like rods or needles and range from macroscopic to microscopic in size. In the present paper, a method for producing silicon rubber that contains the magnetic clusters is presented and its magnetic, mechanical, and physical properties are discussed. This new material shows superpara and anisotropic magnetization. In addition, the tensile strain of the material in relation to normal stress changes due to the existence of the magnetic clusters is studied. This material can be used in engineering applications.

Substructure Pseudo-Dynamic Tests on Seismic Response Control of Soft-First-Story Buildings

Soft-first-story structures, such as piloti buildings, are known as vulnerable structures against earthquakes. In this chapter, a simple scheme for reducing the structural damage of such buildings is proposed. Its effectiveness is experimentally examined through substructure pseudo-dynamic tests. In the proposed method, low yield strength steel devices are applied as elasto-plastic dampers at the first story of the buildings to reduce the seismic response and damage. A six-story single-span piloti model, with or without steel dampers, are the subject of the test. The behavior of the two exterior columns at the first story and the steel damper are tested. The substructure pseudo-dynamic tests are successfully performed to investigate the elasto-plastic behavior of the damper and the reinforced concrete columns at the soft-first-story, as well as the overall structural performance. The experimental results show that the seismic damage of piloti buildings can be reduced with steel dampers, which have been found to work as effectively as expected.

New magnetic viscous damper with intelligent or smart fluid for the next generation

We propose a new viscous damper using magnetically responsive fluids, whose viscous damping factor can be changed by application of a magnetic field. The used fluids are intelligent or smart fluids; MF (magnetic fluid), MR fluid (magneto-rheological fluid), and MCF (magnetic compound fluid). The damper was developed in order to avoid the sedimentation of the fluid particles and to allow the viscous damping factor to be changed by using a fluctuating magnetic field as a semi-active damper. This solves the most important problem of the previous MR fluid damper, that is, sedimentation of the particles of the fluids. We experimentally investigated the dynamic characteristics of the newly developed damper having magnetically responsive fluids. The damper is a spring and mass single-degree-of-freedom system. We dealt with the vibration in a low frequency range, less than 10Hz, for the purpose of damping in architectural applications. A comparison of the differences of the damping effects of the three kinds of the fluids, MF, MR fluid, and MCF, showed that MCF has the largest damping effect. MCF is a new intelligent fluid developed by us for the purpose of having more apparent viscosity than MF and more stable particle dispersion than MR fluid. The experimental results can be explained by the cluster of particles aggregating in the form of a chain or necklace, as observed by microscope.

EFFECT OF FLEXURAL FAILURE-TYPE HYSTERESIS MODEL CONSIDERING SLIP BEHAVIOR ON THE SEISMIC RESPONSE OF RC STRUCTURES

In this paper, to improve seismic response estimation for medium and low-rise RC buildings during aftershock, a hysteresis model which was modified from TAKEDA model was proposed. The modified model was added slip behaviors in loading and unloading processes to TAKEDA model. Time history response analysis using the modified model and TAKEDA model were done to examine the accuracy of the estimated seismic response by comparing with test results. As a result, the hysteresis and period characteristics and the residual displacement calculated by time history response analysis using the modified model were confirmed to give good agreement with experimental data.