A method for predicting the structural behavior of an object when a fire is applied to it for a given period of time, comprising the following steps: Preparing a computer-implemented 3D Finite Element Model of said object including its thermal relevant material properties and a computer-implemented 2D Finite Volume Model for simulating a fire inside said object and obtaining predicting information regarding its thermal effects; Obtaining the heat transfer coefficients of the structure using said predicting information regarding the thermal effects inside said object; Applying said heat transfer coefficients and other relevant thermal boundary conditions in said 3D Finite Element Model, simulating the application of a fire to said object and obtaining a thermal mapping of the object during said application of fire. The invention also refers to a system for carrying our said method.