The main research objective of this paper is to understand the load carrying mechanisms of reinforced concrete structures when subjected to fire. In particular, this research will focus on catenary action of reinforced concrete beams, which is one of the main strategies of providing structural robustness, in the form of the tying method. Catenary action can only be activated if there is axial restraint to the beam. The research was carried out using the commercial finite element package TNO DIANA. The behavior of an axially restrained beam goes through three stages: initial compression due to restrained thermal expansion, followed by almost pure bending when the axial force in the beam is very small, then transits to catenary action when the concrete is cracked and the tensile force in the reinforcement steel resists the applied catenary tensile action, until fracture of the tensile reinforcement steel.