SEISMIC ASSURANCES

The seismic ruggedness of an Armstrong suspended ceiling was demonstrated by shake table testing. The test ceiling and an individual ceiling panel are illustrated below.  Before Armstrong could place this product on the market, they had to assure themselves of its capability of withstanding the earthquake environment of the Western United States. The ceiling product is easily installed onto 15/16" T-bar grid and is downwardly accessible. The panels were designed for use primarily in corridors and lobbies; however, the design allows for the use of metallic ceiling tiles, which are ideal for critical facilities requiring cleanliness, such as food and pharmaceutical processing, semi-conductor manufacturing and medical treatment areas.

UBC REQUIREMENTS MET

ANCO proposed a test program to document the seismic performance of the new ceiling system during simulated earthquake motions which may occur in Seismic Zones 2A, 3, and 4 as defined by 1988 and later versions of the Uniform Building Code (UBC). Towards that end, a 14 by 24 foot ceiling was installed to UBC requirements on ANCO's R-4 overhead shake table. A 30-second earthquake time history was developed which represented the expected motions of the third and sixth floors of a six-story moment-resistant steel frame structure located on a soft soil site. This mid-rise structure was chosen since significant structural amplification of ground motion would occur within the amplified region of the UBC design response spectrum. Test amplitudes were then scaled up or down so that response spectra computed from measured test input motions enveloped the in-structure floor response spectra for Zones 2A, 3, and 4 for non-structural components supported within critical facilities.

CEILING EXCEEDS ZONE 4

The ceiling performed well up to and beyond the high seismic requirements of the Western United States (Zone 4). Minor damage occurred at higher levels when the shake table was commanded to displace more than its displacement limits would permit, resulting in multi-g impact loads. Had severe impacting not occurred, the entire ceiling system would have survived the most demanding tests without any evidence of seismic exposure. Seismic ruggedness of the ceiling system, under normal Zone 4 excitation, was clearly demonstrated.

OVER 10 YEARS EXPERIENCE

ANCO has been involved in testing ceiling components since 1981 and, in addition to Armstrong, has worked with the National Science Foundation (NSF), Ceilings and Interiors Contractors Association (CISCA), Chicago Metallic Corp., and other ceiling component manufacturers to improve the seismic performance of their products and to evaluate the efficacy of a variety of proposed code changes.