Thermal performance of non-load-bearing cold-formed steel walls under different design fire conditions

摘要

Most previous fire experiments of cold-formed steel (CFS) walls focused on the ISO 834 or the E119 fire curve. Although the fire performance of CFS walls under ISO 834 or E119 curve can be theoretically converted to that under other fire curves, the corresponding time equivalency methods have not been experimentally examined. This paper presents an experimental investigation of non-load-bearing CFS walls under four different fire conditions. It is proved by the experiments that the maximum temperature of the design fire curve is one of the most important indexes for representing the severity of fire exposure. Especially, the maximum temperature of 680 degrees C for external fire was not severe to the present non-load-bearing CFS walls. Two specimens were subjected to 285 min of external fire but demonstrated an almost steady-state heat transfer process. Meanwhile, the hydrocarbon fire and realistic design fire demonstrated much more severe damage. It is also proved for the first time that neither the equal area method nor the energy-based method was suitable for the fire-resistance time equivalency of CFS walls. Based on post fire observation, significant local crushing of studs was identified, especially after the fall off of fire-side sheathing. Additionally, it was found that replacing the fire-side base-layer gypsum plasterboard with low-bulk-density calcium-silicate board extends the insulation and structure performance of CFS walls under fire conditions. Moreover, a simplified temperature distribution model and the critical temperature on the fall off of fire-side gypsum plasterboard were recommended for the numerical modeling of CFS walls.