Which methods is the correct procedure for the structural fire test with load?

(1) Residual concept - no load during fire phase and only apply load during post-fire phase until fail

(2) Preloaded until initial crack then the load remain constant during the fire and cooling phase

(3) Gradually apply load from zero during fire phase and stop when fail

(4) Constant load during fire and cooling phase, then apply load during post-fire phase until fail