Influence of different gypsum plasterboards on the fire performance of cold-formed steel walls

As typical fire protection sheathings, the thermal physical properties of gypsum boards may vary among manufacturers, which may affect the fire performance of gypsum-sheathed cold-formed steel (CFS) walls. Six different gypsum boards were selected for the sheathing of six mid-scale, non-load-bearing, CFS wall specimens, and fire tests were conducted under ISO 834 conditions. The results indicated that the insulation performance of gypsum boards may be related to the density and fibre content of gypsum boards. High-density gypsum boards have an improved heat absorption capacity. Adding fibre to the gypsum boards can effectively delay fire-induced fall-off of the gypsum boards. When gypsum boards with no visible fibre exhibit fire-induced fall off, their cold surface temperature fell between 560 °C and 710 °C, while that for gypsum boards with obvious fibre contained in fire exceeded 780 °C. Hence, from the perspective of safety, the performance variation of gypsum boards caused by different manufacturers should be considered in the fire design of CFS walls. A new prediction criterion was proposed to determine fire-induced fall-off of gypsum boards, namely, the cold surfaces of gypsum boards reaching 550 °C and a heating rate above 40 °C/min. The new criteria can clearly quantify the fire-induced fall-off time and temperature of gypsum boards according to their time–temperature curve. In addition, it is suggested to adopt fire-resistant gypsum boards as face-layer sheathing and to adopt standard gypsum boards as base-layer sheathing to make gypsum-sheathed CFS walls more cost-effective.