BTU is an omni-directional load-bearing spherical balls mounted inside a restraining fixture, having the task to bear the structure weight with a neglecting vertical deformation

This paper describes an experimental investigation conducted on WRS-BTU seismic isolators that are constituted by a wire rope spring coupled with a ball transfer unit. The device can be considered rigid along the vertical direction while the horizontal stiffness can be independently chosen to shift the natural period away from the period range having the most of earthquake energy. Two kinds of tests were carried out: the first ones regard the isolator characterization; then, to evaluate the isolation efficiency, a small laboratory structure was equipped with four isolators and several tests on a shake-table were performed.