10.21: Post‐fire response of slender concrete‐filled steel tubular columns

Abstract

In this paper, a fiber beam model for the simulation of the post-fire response of slender concrete-filled steel tubular (CFST) columns is presented. First, the model is validated against experimental results and subsequently it is employed to analyse the post-fire response of circular CFST columns. Actually, when a fire takes place in a building, the columns are supporting load even while the fire is being extinguished. For that reason, it is important to take into account this loading condition when trying to predict their post-fire behaviour. Therefore, in this research, the analysis is initiated when a constant load is applied to the column and, simultaneously, the specimen starts to be heated following an established heating regime (ISO 834). Maintaining the applied load constant, the cooling stage prolongs until the column reaches the room temperature. The post-fire response of the CFST columns is studied by means of a mechanical analysis where the applied load increases progressively up to the column failure. The model considers realistic features typical from the fire response of CFST columns, such as the existence of a gap conductance at the steel-concrete interface or the sliding and separation between the steel tube and the concrete. Finally, the post-fire response of CFST columns is studied in depth taking as reference experimental results used in validation. The variation of the residual strength with load level for realistic fire resistance times is calculated and analysed.