Theoretical estimation of critical fire load close to an unprotected steel member

A theoretical model is set up to estimate critical fire loads close to unprotected steel members in large rooms. The members are assumed to have a critical temperature calculated from external loads. A constant fraction of the energy of the fire load is assumed to be absorbed by steel during burning. Rapid overall and zone burning with constant velocity are shown to yield the same critical fire load. Therefore it is concluded that these loads also give conservative estimates for the critical load in a real fire, the development of which lies between these two extremes. A general form of calculation is given. For rough estimates, 5% mass of the fire load as compared to the steel m