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Shake-Table Seismic Performance Evaluation of Direct- and Indirect-Hung Suspended Ceiling Systems

ABSTRACT Suspended ceiling systems are among the most frequently reported earthquake-vulnerable nonstructural elements. Despite their importance, a rational seismic design procedure for suspended ceiling systems has not been developed because of their complex details and behavior. In this study, the seismic performance of direct- and indirect-hung suspended ceilings was evaluated based on shake table tests. In particular, a large-size ceiling specimen, comparable to an actual constructed size, was tested using an array of two shake tables and a highly stiff test frame with overall dimensions of 13 (length) × 5 (width) × 3 (height) m. In addition, six smaller specimens were tested using one shake table. All the specimens were prepared as free-floating systems by permitting free movements at the four edges. Based on the test results, key engineering parameters related to acceleration amplification and natural frequency were identified and the overall seismic performance was evaluated. Compared with the extensive failure observed in the lay-in panel ceiling specimens, marginal damage occurred around the pounded edge in the continuous panel ceiling specimens because of the robust restraining effects of the screw-attached panels on the ceiling grid members. The median amplification factors observed in the tested suspended ceiling specimens were about 1.80 and 1.75 for the vertical and horizontal directions, respectively. The dynamic behavior of the tested indirect-hung suspended ceilings which used long hanger bolts was significantly different from the pendulum behavior observed in the direct-hung suspended ceilings. The unidirectional rotation-restraining characteristic of the hanger bolt connection imparted different behaviors in each orthogonal direction. The natural frequencies of the tested suspended ceilings were well predicted when the deformed shape of the hanger bolt was modeled as a single curvature bending in the rotation-free direction and a double curvature bending in the rotation-restrained direction. The damage evaluation of each ceiling system was also presented through incremental-intensity shake table testing.