Seismic vibration control of suspended ceilings in electronics factories

In the semiconductor and liquid crystal display (LCD) industries, suspended ceilings are widely used in wafer and LCD panel fabrication plants (fabs). Despite several preventive measures having been taken, substantial financial losses have been incurred in past earthquakes, with one of the main causes attributed to damage or collapse of ceilings due to excessive ceiling sway during earthquakes. A practical approach of incorporating customised viscous dampers into suspended ceilings to mitigate their seismic response is described in this article. Unlike the convention in most fabs, where diagonal bracing rods are added between suspended ceilings and the structural floor slab to mitigate ceiling vibration, this new approach installs customised viscous dampers in between the ceiling and the column/wall. An analytical model to simulate the vibration of a suspended ceiling was developed. Shake table tests of the ceiling–structure model were then conducted to verify the effectiveness and feasibility of the proposed approach. The results indicated that, when equipped with viscous dampers, the displacement responses of a suspended ceiling can be significantly reduced. Incorporating the dampers into the ceiling with added bracing rods was found to give the best seismic performance.