Experimental and Numerical Study of a Plasterboard Suspended Ceiling System with "Free" Perimeter Supports

Poor earthquake response in suspended ceilings can cause wide-scale injuries and financial losses, which underscores the need to understand such systems better. This paper presents a study on a plasterboard suspended ceiling system (PSCS) installed in a 3.00-m tall steel building. The PSCS is an assembly of a plasterboard with plan dimensions of 2.69 m×2.27 m attached to a horizontal metal frame suspended from the roof. The building was subjected to Taft motion in the principal horizontal directions. The peak input accelerations ranged between 0.05g and 0.25g (0.05g and 0.70g) in the short-edge (long-edge) direction; the natural period of the PSCS increased from 0.91 to 0.99 s (0.32 to 0.99 s) during the tests. The peak plasterboard acceleration ranged between 1.1 and 2.4 times the peak roof acceleration (except during impact). Damage was observed primarily in the suspender struts near its lower end, attributable to the "rigid"connection between strut and horizontal metal frame. Response of the PSCS in the "softer"direction was greater and more sensitive to the response of the superstructure compared to the orthogonal direction. Static tests on the joint between the suspender and the roof of the building provided information for the development of the numerical model. Separate models were developed for the two principal horizontal directions due to different degradation characteristics. An ambient damping of 2% in the numerical model (experimental value was 8%) led to a much better simulation in the "softer"direction, indicating that damping during "large-amplitude motions"can be considerably less than that during "low-amplitude motions."