Fire is a hazard and a building’s structure must be designed to maintain their structural stability when exposed to fire. Fire safety design of structures can be done following the prescriptive codes or carrying out a performance-based design. Prescriptive fire design codes describe how buildings should be built to fulfil generic fire resistance requirements depending on their use, height, or compartment area. Performance fire design allows derivation of structural fire resistance of buildings by characterizing the fire dynamics within a compartment and analysing the thermal and mechanical response of the structures. Travelling fires methodology (TFM) characterises the fire dynamics for the performance-based design of large compartments, which assumes that as fires burn, they travel along the compartment floor as flames spread. TFM is a design tool based on several assumptions. This thesis revisits and addresses its near field assumptions and applies a probabilistic model to assess the reliability of a structural element exposed to travelling fires and the uniform temperature ﬁre.