The thermal modelling of structural piping systems under fire conditions

This work presents a finite element formulation to model the thermal behaviour of structural piping systems under fire conditions. The study of steel structures at elevated temperatures needs the thermal action characterisation and the non-linear material behaviour, according to the Eurocodes standards. The surrounding fire temperature in structural systems is in accordance with ISO 834. Structural piping systems may have also, internal voids filled with air that needed to be simulated. In this domain, the internal temperature may be calculated with some simplified formulas obtained from heat transfer equations. For small values of the pipe thickness-mean radius ratio, the thermal behaviour may be determined with high accuracy using one dimensional mesh approach, for axisymmetric thermal boundary conditions, across pipe sections. The transient temperature evolution in piping systems and the internal temperature in the voids will be calculated. Conclusions are presented regarding the importance of the temperature field obtained in structural piping systems using one and two dimensional finite element meshing and results will be discussed for various study cases. Numerical results will be compared with other finite element commercial code, Cosmos/M, for the same situation