Frequency‐Sensitivity of the seismic damage to suspended ceilings

Seismic damage to suspended ceilings was frequently reported even in minor to moderate earthquakes and caused problems to immediate occupancy and quick recovery of buildings. While peak floor acceleration (PFA) has been exclusively used as an intensity measure for suspended ceilings, this study introduces a shake table test on minimum subassemblies of suspended ceilings under sinusoidal excitation to critically assess the rationality of this practice. The test results show a significant frequency-sensitivity of the ceiling damage that, depending on the dominant frequencies, an excitation of a lower PFA might cause much severer damage than that of a higher PFA. A numerical model that captures the nonlinear interaction of the individual components in a suspended ceiling, that is, the main and cross runners, ceiling panels, a hanger, and enclosure angles, is established and calibrated to simulate the frequency-sensitive behavior observed in the shake table tests. The model is then extended for suspended ceilings of realistic dimensions. Three-dimensional fragility spectra of suspended ceilings under sinusoidal excitations are proposed to relate the extent of seismic damage with not only the PFA but also the excitation frequency. Boundaries of damage limit states can be defined by taking two-dimensional sections on the fragility spectra, based on which, the influence of key factors on ceiling damage characteristics is illustrated.