Seismic vibration control of discontinuous suspended ceilings in semiconductor and LCD fabs

In semiconductor and liquid crystal display (LCD) industries, suspended ceilings are widely used in wafer and LCD panel fabs. Despite several preventive measures been taken, substantial financial loss was reported in the past earthquakes, and one of the main causes was attributed to damage or collapse of the ceilings due to excessive ceiling sway during earthquakes. This paper proposes a practical approach of incorporating customized viscous dampers into the suspended ceilings to mitigate their seismic response. Unlike conventionally been done in most fabs where diagonal bracing rods were added between suspended ceilings and structural floor slab to mitigate ceilings’ vibration, it is proposed to install customized viscous dampers in between the ceiling and the column/wall. An analytical model to simulate the vibration of a suspended ceiling is first developed, followed by shake table tests of the ceiling-structure model to verify the effectiveness and feasibility of the proposed approach. Results indicated that when equipped with the viscous dampers, the displacement responses of the suspended ceiling can be significantly reduced, and incorporating the dampers into the ceiling with added bracing rods is shown to give the best seismic performance.