Assessing construction elements with lower fire resistance rating under big fires

There are proposals on using fire resisting construction and structural elements with fire resistance ratings lower than the values specified in the fire codes. The equal temperature-time exposure concept or t-equivalent rule is commonly applied to support the argument. However, there are concerns in applying such an approach for bigger fires as the radiative heat flux acting on the construction element is not included. Fire hazard assessment on that should be watched. This is a short note on discussing possible problems associated with fire resisting construction with lower ratings. Full-scale burning tests with bigger fires are suggested to support the argument and to demonstrate that the equal temperature-time concept would work as expected.