A simplified model to evaluate the variation of internal forces in steel structures subjected to fire

Using modern software, there is the possibility of evaluating the structural response in fire conditions, conducting advanced thermo-mechanical analyses and taking into account the thermal- induced indirect actions that may arise in the event of fire. These effects may affect the internal stresses of the structural members compared to the normal temperature conditions. Sometimes these advanced analyses are complicated arising significant computational burden, so a simplified method aimed to simulate or interpret the interaction between the adjacent members of the structure and to evaluate such thermal-induced stresses in case of fire, would be useful. In order to perform simplified but realistic analyses on steel members, in this paper, a non-linear procedure, based on analytical expressions, is proposed.