The authors proposed the methodology of carrying capacity determination of steel-concrete beams with external steel sheet reinforcement under thermal and power impacts. It’s assumed standard temperature range of fire in the room and instantaneous load. The strength calculations were provided in order to determine bending stress and beams deflection due to support conditions of the beam. The mineral wool coat Rockwool series Conlit SL150 were used as the beam fire protection. Described researches were done taking into account the basic conditions of beams loading and bearing as well as non-linear “stress-strain” dependencies of concrete and external steel reinforcement.