Advances in seismic qualifications of suspended ceilings: Results of NEES-GC initiative

An ongoing study within the framework of the project on seismic behavior of nonstructural components, sponsored by the research program of the National Science Foundation's Network for Earthquake Engineering Simulation (NEES), is developing a new testing facility for suspended ceilings and other systems, for use with either single or tandem shake tables. The experimental facility is necessary for the evaluation of full size suspended systems for which modeling is either too complex or cost inefficient. Moreover, in the frame of the aforementioned research, methods of analysis and design are being developed. The authors developed a large frame to test a continuous suspended ceiling of up to 20 x 50ft (1,000 ft.²). The frame has dynamic characteristics with variable frequencies characteristic to typical roofs (or floors) for the suspension of ceilings and flexible walls. However, the frame cannot deliver precisely the desired "floor" motion unless a special procedure is employed. Such procedure using interactive control principles was developed to provide a "command drive" signal to the shake table in order to obtain a "desired floor motion" at the roof level. The combined designs of the physical frame and of the shake table motion allow for testing a variety of suspended systems while eliminating side effects of high frequency ringing or wall distortions. The paper describes the design parameters and introduces the motion design procedure, which can be implemented in any experimental facilities as well.