A new temperature–time curve for fire-resistance analysis of structures

To evaluate the fire-resistance of large space buildings, smoke temperature distribution in large space fires is one of the required conditions for determining the temperature elevation history in structures. However, full scale fire experiments on large space building in State Key Laboratory of Fire Science in China revealed that the fire temperature distribution in large space fires are different with that in small compartment fires. In order to standardize the hot smoke temperature in localized fire, a number of ventilated fire scenarios are designed with ceiling height ranging 4–20 m high, floor area ranging 500–6000 m2 and the rate of heat release ranging 2–25 MW. A wide range of result from a series of large space fire scenarios simulated by FDS (Fire Dynamics Simulator), revealed three important facts. Firstly, temperature distributions throughout the large space fire are non-uniform and pole asymmetric from the fire source. Secondly, the key factors i.e. fire growth type, heat release rate, dimension of internal space and fire area have significant influence on the temperature distribution. Thirdly, with the increase of heat release rate, the maximum temperature is higher and with the increase of the floor area or the internal space height, the maximum temperature is lower. The temperature decays from the plume centerline in horizontal plane. Finally, a new parameter equation that represents the non-uniform fire temperature distribution as a function of time and key factors has been developed by parametric analysis method based on results from numerical tests by using FDS. The new parameter equation agrees well with the numerical test and can be used as the temperature boundary conditions for the lumped differential formulation, from which the transient temperature in elements can be derived. In the meantime this equation can be available for global structural analysis exposed to localized fires.

► A new time–temperature curve based on numerical tests has been developed by the parametric method.
► This new curve describes the transient non-uniform temperature distribution for localized fire.
► Fire growth type, heat release rate, dimension of internal space and fire area are key factors.
► These four factors are taken into account while developing the new curve.
► This new curve can be used as the smoke temperature boundaries for structural fire-resistance.