Hollow-core seismic base isolation bearings using crumb- Rubber composite for residential construction

Elastomeric base isolation systems are proven to be effective in reducing seismic forces transmitted to buildings. However, due to their cost, the use of these devices is currently limited to large and expensive buildings. The application of such systems in smaller structures, such as residential buildings, depends upon the ability to reduce the cost while maintaining functionality under the corresponding lighter loads. A feasibility study was conducted to investigate the use of Crumb Rubber (CR) to develop base isolation devices for use in residential masonry construction. The mechanics of particulate composite based on shear theory was employed to design the mix recipe and two different CR materials were made using particulate and fibrous crumbs as filler in polyurethane matrix. Static tests based on ASTM Standards were performed to determine mechanical properties of these CR materials. Hollow core single layer bearings were constructed and shake table test was performed to evaluate their dynamic characteristics. The effects of pressure and thickness on dynamic performance of these bearings were experimentally determined and the results were compared with analytical values. The mechanical properties were consistent over a wide range of pressures and good correlations were observed between the experimental and the analytical results. These results indicate that a desired natural frequency can be obtained for a single layer mat made of either material by controlling the pressure on the bearing and the thickness of the layer. Thicker mats will require reinforcement to increase vertical stiffness while decreasing the amount of bulging.