PILLOW-SHAPE BASE ISOLATION SYSTEM AND ITS SEISMIC BEHAVIOR

One way to reduce the seismic response of structures is base isolation. In this paper a new isolating system is introduced for short to mid-rise buildings that unlike conventional systems such as LRB and HRB, does not need cutting edge technology and has low manufacturing cost. This system is made up of two orthogonal pairs of pillow-shaped rollers that are located between flat bed and plates. By using this system in two perpendicular directions, building can move in all horizontal directions with respect to its foundation. Due to the pillow shape of the roller, this system has self-centering capability which causes it to return to its original position after the earthquake. The rolling friction force between pillows and their bed creates some damping in the system which prevents it from further oscillationafterearthquake excitations diminish. The purpose of this study is to evaluate the proposedisolationsystem’s performance under different earthquake excitations. First of all general features of the proposed isolators have been introduced followed by the analytical equations of the system. Vertical bearing capacity and the effects of the thickness of pillows has been investigated using ABAQUS software. It has been shown that for a pair of pillows of 58 cm width, 45 cm height and 100 cm length the vertical load bearing capacity of the system is more than 300 tons. Theperiod of system with respect to the height and radius of curvature of the rollers, and seismic response of a building, assumed as a rigid body resting on isolators, has been studied subjected to simultaneous effects of horizontal and vertical excitations. It has been shown that the proposed system can reduce the absolute acceleration in the building around 78% in average, while the building’s maximum displacement is around 1.77 times of the ground in average.

Keywords:

Rolling Isolation , Lagrange Equation , Runge-KuttaTechnique , Finite Element Analysis