Fuminobu Ozaki

Damage-Control Systems Using Replaceable Energy-Dissipating Steel Fuses for Cold-Formed Steel Structures: Seismic Behavior by Shake Table Tests

AbstractA system that controls the rocking behavior of multistory shear walls is proposed as an innovative damage-control system for cold-formed steel structures. In this system, we have developed a new hold-down equipped with a fuse function (HDF) that controls the rocking behavior and is placed on the foundation of multistory shear walls. The HDF contributes to reducing damage to both structural and nonstructural members in cold-formed steel framed buildings, dissipating seismic input energy in the event of a large earthquake. The present paper describes the shake table tests performed using one-story, one-span, real-size specimens to investigate the fundamental behavior of the developed system. By using shake table tests in which the type of hold-down and the magnitude of input ground motion were varied as parameters, it was clarified that the plasticization of HDFs could reduce the base shear of specimens and that the energy dissipation by the HDFs could subdue the uplift deformation of the specimens....

Probabilistic hazard model of inelastic oscillator based on semi-theoretical solutions of first passage problem

In this study, an approximate method of estimating the exceedance probability of the maximum ductility factor of an inelastic oscillator is proposed based on the equivalent linearization technique using the capacity spectrum (CS) method. The CS method seeks to determine the first point at which the demand spectrum crosses the CS. Because the auto-correlation function of the response spectrum is only a function of the difference between the logarithms of two natural periods, the CS method can be interpreted as the first passage problem of a stationary standard normal stochastic process. Because the auto-correlation function is not continuous when the difference is equal to zero, and because the crossing event cannot be modeled as a Poisson process when the CS is close to the horizontal axis, the mean crossing rate is semi-theoretically estimated based on Monte Carlo simulation. The results are further modified to create a general model. The accuracy of the proposed method is demonstrated by using numerical examples.