Traditionally, the prescriptive approach developed from the standard fire tests have proved to be an adequate and effective for ensuring a minimum level of fire safety to buildings. The direct application of the fire test results can be easily understood and applied by designers and checking authorities.

However, this method has generally been considered to stifle the structural engineer’s understanding of how buildings behave in fire. The main limitations include:

1. The structural elements of a building do not work independently as treated in a standard fire test. The interaction between structural elements in a fire has both a possible beneficial and detrimental effect on the survival of the building as a whole. Beneficial effects are generally due to the formation of alternative load-path mechanisms such as compressive and tensile membrane action, catenary action and possible rotational restraint from connections. The detrimental effect can be due to restraint of thermal expansion resulting in large compressive forces being induced into elements, particularly vertical elements, which then causes instability.
2. The standard curve does not represent a real fire, which generally comprises three distinct phases: growth, steady burning and cooling (or decaying). The severity of a real fire in a compartment is governed by the geometry of the compartment, amount of combustible material, ventilation conditions and thermal characteristics of the compartment boundary. Different types of fire can result in different structural behaviour. For example, a short duration high temperature fire can result in spalling of concrete exposing steel reinforcement due to the thermal shock. Whereas a long duration low temperature fire can result in a higher average temperature in the concrete members resulting in greater thermal expansion and a greater overall reduction in concrete strength.
3. The development on optimising the structural performance at the ultimate and serviceability conditions and advancing the construction technology is an on-going process. However, the current prescriptive rules for structural elements are largely developed based on the testing findings of the 1946 Fire Grading Report (MPBW 1946), which is over 50 years old. It is questionable to assume the prescriptive rules developed from outdated tests on different forms of construction and subject to different loads can be applied to these new forms of construction.