Seismic Protection of Equipment in Essential Multistory Buildings with Lead-Rubber Bearing

Sunday, February 14, 2016
Xing Han, Howard University, Washington, DC
Essential buildings are equipped with specialized high-tech, communication, power equipment and other relevant pieces of equipment and components. To avoid disastrous seismic impacts on essential buildings due to loss of functionality of this type of equipment, the engineering of seismic mitigation mechanisms within the equipment is necessary. Low damping rubber and lead-rubber bearings are widely used in building and bridges to enhance their seismic performance. However, applications and experimental evidence on the effectiveness of seismic isolation system for protection of equipment in multistory buildings is lacking. This study is to (1) evaluate the effectiveness of a lead-rubber isolated platform for seismic protection of equipment; (2) evaluate the capability of the platform to control earthquake accelerations and displacements of the supported equipment when subjected to both ground and floor accelerations. Scaled earthquake simulation tests were performed on a lead-rubber isolated platform supporting simulated equipment. The lead-rubber bearings used in the platform was tested in a previous study as low-damping rubber bearings. The insertion of lead rods into low damping rubber bearings significantly enhanced the energy dissipation capacity of the platform. Both ground and floor accelerations from historic earthquake events were input onto the platform-equipment setting. The isolated equipment acceleration responses evidenced their sensitivity to the building floor levels. Sample responses illustrate that the platforms based on lead rubber bearings are able to control the horizontal accelerations and displacements on the equipment when subjected to ground and floor accelerations. Results from the lead rubber platform demonstrate feasibility of achieving isolation of accelerations at roof levels. The displacement levels of the prototype system are feasible for seismic protection for equipment at roof levels. The isolated platform did not show any sign of stiffness reduction in the horizontal direction during the scaled test. Further studies on the stability of individual bearings and isolated platform in the prototype scale and on the dynamic interaction of the isolation platform with the building are required. Additional effective damping on the platform is able to enhance the acceleration and displacement responses of the platform.