Seismic Behavior of Suspended Ceilings

The earliest experimental work in the area of seismic behavior of suspended ceilings dates back to 1983 by ANCO engineers, CA [1]. After that there were a series of tests followed in the next decades, notably, by Yao [2] and Badillo [3]. The shake table tests for the large scale (area more than 400 ft²) have been conducted at University at Buffalo by Ryu [4]. In these series of tests, several parameters such as the weight of the panels, the area of the ceiling, the nature and intensity of the seismic input are considered. The tests were conducted in two configurations, a relatively small area ceiling with an area of 400 ft². The second configuration is the ceiling with the area more than 1000 ft². The tests conducted at University at Buffalo for the above are system-level tests. No component level tests were conducted.

Soroushian [5] has conducted component level experiments at the University of Reno, for the ceiling components. They have estimated the capacity of the hanger wires, the shear strength of the grid connections in both minor and major axes. Also, they have conducted tests to derive the moment capacity of the connections in both major and minor axes. In [6], Soroushian derived the fragility curves for the components. Utilizing the several data from the experimental studies, the backbone curves using the Pinching4 material in OpenSEES were derived for the grid connections. The nonlinear backbone curves for the shear in major axis, the shear in minor axis, the moment vs rotation in both minor and major axes have been derived.

However, the grid components used to test in University of Nevada, Reno were not the same grid components utilized in the large area ceiling tests at Buffalo. Hence, a numerical model that accurately depicts the failure of the connections has to be developed. By varying the configurations in the numerical model, the approximate connection details can be derived. These connection details can be utilized to develop a numerical model that could accurately predict the response of the suspended ceiling system that was tested using shake table tests at University at Buffalo. Once a reasonable estimation of the model is completed, then the model could be utilized to develop fragility curves for ceiling systems of various configurations under seismic loads.

In Fig. 1. Depicts the suspended ceiling for the shake table tests at University at Buffalo. The dimensions of the ledge are 20 ft x 20 ft. Fig.2. represents the testing of the shear strength in the major axis for the ceiling components as part of the numerous tests done at University of Nevada, Reno. Numerical models were developed by [7] using SAP2000. They have also conducted a parametric study to understand the effect of parameters on the behavior of the model. Another detailed numerical model was developed by [1] in OpenSEES. The model was successful in accurately predicting the initiation of the damage in the ceiling system. The issue with these models is that they could not capture the propagation of the damage in ceiling systems after the initial failure. Hence a three-dimensional detailed finite element model is necessary to model the accurately predict the propagation of damage in such a system. This study aimed at developing the model in detail. ABAQUS software, due to its efficient documentation has chosen to develop this model.

Once a reasonable numerical model that could accurately capture the behavior of suspended ceilings is developed, then it could be utilized to understand the behavior of the system under a wide range of circumstances. Also, the configuration of the suspended ceilings influences its seismic behavior. A numerical model is an efficient way to understand the effects of this phenomenon compared to the expensive experimental tests. Hence this study is focused to enrich the knowledge and understanding of the suspended ceilings that are so commonplace in today’s modern offices.

References

[1] Zaghi, A. E., Soroushian, S., Echevarria Heiser, A., Maragakis, M., & Bagtzoglou, A. (2016). Development and Validation of a Numerical Model for Suspended-Ceiling Systems with Acoustic Tiles. Journal of Architectural Engineering, 22(3), 04016008.

[2] Yao, G. C. (2000). “Seismic performance of direct hung suspended ceiling systems.” J. Archit. Eng., 10.1061/(ASCE)1076-0431(2000)6:1(6), 6–11.

[3] Badillo-Almaraz, H., Reinhorn, A.M.,Whittaker, A. S., and Cimellaro, G. P. (2006). “Seismic fragility of suspended ceiling systems.” Technical Rep. MCEER-06-0001, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, NY.

[4] Ryu, K. P., & Reinhorn, A. M. (2019). Experimental study of large area suspended ceilings. Journal of Earthquake Engineering, 23(6), 1001-1032.

[5] Soroushian, S., Maragakis, E. M., & Jenkins, C. (2015). Capacity evaluation of suspended ceiling components, part 1: experimental studies. Journal of Earthquake Engineering, 19(5), 784-804.

[6] Soroushian, S., Maragakis, E. M., & Jenkins, C. (2015). Capacity evaluation of suspended ceiling components, part 2: analytical studies. Journal of Earthquake Engineering, 19(5), 805-821.

[7] Echevarria, A., Zaghi, A. E., Soroushian, S., & Maragakis, M. (2012, September). Seismic fragility of suspended ceiling systems. In 15th World Conference on Earthquake Engineering (15WCEE) (pp. 24-28).