Effects of Foundation Stiffness on Vibration Behavior of Secondary Structures Due To External and Internal Excitations

In this paper, the vibration behavior of a secondary structure in a frame structure under combined excitations of external earthquake and internal production machinery is investigated. The effects of stiffness of the foundation springs of the primary structure on dynamic behavior of the secondary structure are evaluated. The primary structure is modeled by FEM in which consistent mass and Rayleigh damping matrices are adopted. The secondary structure consists of one mass connected to a beam mounted on a member of the primary structure. Numerical results show that the foundation stiffness has considerable influences on relative displacement response of the secondary structure and provide guidelines for the seismic design of factory buildings with production machinery.