Axial and Shear Behavior of Prestressed Damping Isolation Units Using a Spring and Rubbers

This study investigated the axial and shear behaviors of a seismic damping isolation unit (SDI) developed to improve the seismic resistance of suspended ceiling structures. To enhance the energy dissipation of the SDI, it was composed of a spring, embossed rubbers, and prestressed bolts. Twelve specimens were prepared and tested for failure under axial and shear loading. The main parameters were the presence or absence of a spring, loading type, and magnitude of the prestressed force introduced to the bolts to connect the embossed rubbers. The test results showed that in the relationship of axial or shear load–displacement of the SDI, the post-peak behavior tended to be more ductile for specimens with a spring or higher prestressed force magnitude. Consequently, the ductility ratio and equivalent damping coefficient of the SDI with the spring and 0.1fby were 3.81 and 0.166, which was 1.06 and 1.20 times higher than the specimens without spring and prestressed force. In addition, the ductility ratio was approximately 1.07 times higher for the SDI specimens subjected to monotonic loading than for those subjected to cyclic loading. Meanwhile, the JIS B 2704−1 and AISC specifications estimated the tensile strength of the SDI specimens subjected to monotonic loading well, but overestimated that of the specimens subjected to cyclic loading. Hence, the JIS B 2704−1 and AISC specifications should be underestimated by 15.7% and 81.7%, respectively, when estimating the tensile and shear loads of the SDI subjected to cyclic loading.