Keywords: base-isolated structure, displacement-dependent damper, magneto-rheological damper, pseudo-complex-damping rule, shaking table test, numerical analysis.

The displacement-dependent damper which depends only on the damper displacement was suggested by Sagami et al. [1,2]. They showed that the displacement-dependent damper can reduce the maximum damper force compared with a conventional velocity-dependent damper in cases where the displacement of the isolation layer is the same. The complex damping is the ideal model for the displacement-dependent damper. The complex damping, however, is generally considered in the frequency domain and it is impossible to realize because of the noncausal characteristics. To simulate the complex damping in the time domain, Fujita et al. [3] have presented a new seismic control rule denoted as a variable-oval-control rule. In this control rule, the semi-active damper is also used. The proposed control rule, however, has nonlinearity and discontinuity in the hysteretic loop.

Ikago and Inoue [4] have presented the pseudo-complex-damping rule as an alternative of the variable-oval-control. This is a simple control rule to simulate the complex damping theoretically by the active or semi-active dampers. The purpose of this study is to find the feasibility of the displacement-dependent damper by the pseudo-complex-damping rule from the experimental and numerical analysis studies.

From a series of shaking table tests and numerical analyses for the base-isolated structure, incorporated with the semi-active damper controlled by the pseudo-complex-damping rule in the base-isolated layer, it is shown that the hysteretic behavior of the damper, using the pseudo-complex-damping rule, cannot simulate the ideal displacement-dependent damper well because of the simplified assumption for the pseudo-complex-damping rule. In order to improve the pseudo-complex-damping rule, the assumption is revised according to the test results. From a series of numerical analysis, it is shown that the improved pseudo-complex-damping rule can simulate the ideal complex damping to some extent. Still little differences can be found especially in the range of the large displacement, and it is a future challenge to improve this.

1

Y. Sagami, N. Hori, N. Inoue, "A study on control method by magneto rheological fluid damper in base isolated structure", J. Struct. Constr. Eng., AIJ, 627, 709-716, 2008. (in Japanese) doi:10.3130/aijs.73.709

2

Y. Sagami, N. Hori, K. Ikago, N. Inoue, "A study on the displacement control design with complex model of the dampers in base isolation structures", Journal of Structural Engineering, AIJ, 56B, 163-170, 2010. (in Japanese)

3

M. Ikenaga, K. Ikago, N. Inoue, "Development of a Displacement-Dependent Damper for Base Isolated Structures", in B.H.V. Topping, J.M. Adam, F.J. Pallarés, R. Bru, M.L. Romero, (Editors), "Proceedings of the Tenth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 163, 2010. doi:10.4203/ccp.93.163

4

K. Ikago, N. Inoue, "Seismic displacement control of base-isolated structures using complex stiffness model", Journal of Structural Engineering, AIJ, 75, 1653-1660, 2010. (in Japanese) doi:10.3130/aijs.75.1653

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