The Isolation Performance Study Of A New Three-Dimensional Seismic Isolation Pier

Base isolation technology is a new technology which began to rise in 1960 s. Compared to traditional anti-seismic structures, the design philosophy and principle for isolated ones are clear and simple. Thus this new technology has been developing rapidly.According to traditional theories, horizontal seismic effect is decisive to the destruction of structures, whereas vertical seismic effec t only amounts to 1/2–2/3of horizontal one. Hence vertical seismic effect has long been neglected in seismic design. In China’s Code for Seismic Design of Buildings, relevant provisions relating to vertical seismic effect are only made for 9 degree high-rise buildings, 8 or 9 degree long cantilever structures and large-span structures. Affected by this view, most of the existing base isolation bearings can merely isolate horizontal seismic action, rather than achieve the effect of isolating both horizontal and vertical seismic action at the same time. In view of this, the thesis presented a new three-dimensional isolation device-- three-dimensional isolation pier, which could isolate both horizontal and vertical seismic effect simultaneously. The core force member of this three-dimensional isolation pier is the isolation unit(ordinary cylindrical helical compression spring) between the upper and lower blocks. The appropriate horizontal and vertical stiffness can be obtained to achieve the three-dimensional isolation function, by adjusting various parameters of cylindrical helical compression spring.This thesis mainly introduced the working principle, structural features, design philosophy and manufacturing process of three-dimensional isolation pier, as well as the static loading test and shaking table test experimented with this device. Through static loading test, we had measured the vertical bearing capacity, vertical and horizontal stiffness of the isolation pier, and had done comparative analysis with theoretical value. By replacing low town buildings with concrete masses which is great in stiffness, we also carried out shaking table test, collected peak acceleration of rigid block countertop and shaking table with the help of pickup vibration, and made an analysis. The former test results show that, the measured horizontal and vertical stiffness values coincide well with theoretical ones, and the calculation model and design theory is reasonable. The latter test shows that, peak acceleration transmitted to upper structures by isolation layer can be attenuated by more than 50% both in two horizontal directions and vertical vibration, therefore, the isolation pier has good three-dimensional isolation effect. This device is simple in structure and low in cos t, convenient for industrial production, so worth promoting to be applied to low town buildings in high intensity regions.