Will a steel structure still be standing at a temperature past its critical temperature? Or will it be unsafe?

The critical temperature of steel is 550 degrees.

The temperature for cellouslic materials can be given by the formula:

T=20+345〖log〗_10 (8t+1)

Where T is the fire resistance and t is the temperature of the furnance. if t is 550 degrees (critical temperature of steel), this gives a fire resistance of approx 5mins which is too low. So i used a different guidance document

For unprotected steels especially the temperature can be given by:

T=0.54(θs-50)(〖Hp/A〗^(-0.6) )

Where T is the fire resistance, θs is the temperature of the furnance and Hp/A is the section factor of the beam. Taking a 43kg 254mmx146mm beam which is exposed on 3 sides for example, the section factor is 170. taking θs as 550 degrees and Hp/A as 170, this gives approximately 12.4minutes of fire resistance which is also too low.

So what Im trying to ask, is that will a steel beam ultimately collapse at 550 degrees or is 550degrees the temperature a steel beam would start to bend. If so what temperature does a steel structure completely fail and cause a structure to collapse. Any help would be appreciated. Thank you.