Random Response of Inelastic Space Structures Subjected to Bi-Directional Ground Motion

The objective of this paper is to clarify the aseismic safety of the ultimate state of space structures. A method of stochastic earthquake response analysis is presented, which extends the formulation of Y.K. Wen et al. by introducing a yielding condition and its associated flow rule into the differential equations of hysteresis rule. In order to study the effect of bi-directional ground motion on the responses such as ductility, hysteretic energy dissipation of space structures, the parametric analysis of various frequency ratios and strength ratios between perpendicular axes of structures is performed. The responses under bi-directional ground motion are compared with those under uni-directional motion and the effect of deterioration of hysteresis are also studied. As the results of the analysis, the following interesting conclusions were obtained: 1) Standard deviation of ductility response is affected by the frequency characteristics of space structure, especially in the smaller frequency direction, along which smaller ductility response is likely under uni-directional ground motion, 2) The effect of deterioration of hysteresis is remarkable in both axes of structure, especially in the case of bi-directional ground motion, 3) The effect of bi-directional ground motion is greater on the ductility response in the stronger axis of structure than in the weak axis, and when considering the deterioration of hysteresis, displacement responses in both directions increase but the total hysteretic energy dissipation under bi-directional motions is equal or less than that under uni-directional motion

Experimental Study on the Dynamic Characteristics of Isolated Structures

This paper deals with an experimental investigation on the dynamic behavior of single-story and single-bay steel frame structures with or without sliding system at the base by using an electro-magnetic type shaking table. The model structures are composed of four columns which are rigidly connected to the roof and base plates and the sliding mechanism. From the results of the preliminary frictional tests of steel plates as well as the results of the dynamic main tests of isolated structures, it is concluded that the aseismic safety of the upper main structure considerably increases by introducing a sliding mechanism at the base. The response analysis of a system with two degrees of freedom, in which the rigid-plastic hysteresis and the negative damping in the restoring force characteristics of the frictional force are incorporated, satisfactorily duplicates the dynamic behavior of isolated structures