| This paper mainly discusses the stiffness variable isolated protection device of the laminated steel plate rubber bearings. When the lateral distortion of the bearing is too large, which is usually caused by somewhat similar resonance effect from long period ground motions, it will be instability and failure.In order to ensure the safety of the isolated buildings and prevent the failure of rubber bearings from large distortion. Additional spring components can be used which will work together with rubber bearings and then the possibility of further increase of the displacement of rubber bearing is suppressed and reaches the prescribed limitation because the natural period of the base isolation building has been changed, and the story shear forces of the super-structure are only slightly increased. In the course of analyses of this paper, a multi-particle structural analytic model is set up. The motion equations of three states of non-affixation, right affixation and left affixation are deduced. In the course of analyzing practical engineering application and the program, the method of choosing appropriate parameters for the protective device is discussed. Here we also simplify the models of soft collision and the stiffness variable isolated protection device.It indicates that the stiffness variable isolated protection device does not take great effect when encountered moderate or short period earthquake waves. While encountered rare or long period earthquake waves, the device effectively limits the larger distortion of the isolated layer. And protect the rubber bearings from failure. At the same time, the stiffness variable isolated protection device has a good prospect of applying for it is hard, simply, durable, low cost and not effected by structure's analysis model. But in practice, a deeper research of the parameters of the spring device must be taken (e.g. stiffness, elastic distortion) and a higher performance device that put theory into experiment should be developed.
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