Prestressed members under natural fires: a preliminary study on the residual behaviour

The present work is aimed at investigating the residual behaviour of prestressed concrete members exposed to natural fires, since experience has shown that substantial losses of the load bearing capacity may take place during the cooling phase. This topic is of great practical significance, because the knowledge of the residual response can help the engineers to decide whether a structure can be refurbished after being exposed to fire, with minor costs, or whether demolition is inevitable. Sequentially coupled thermo-mechanical analysis was performed on typical inverted T and double T-beam sections, subjected to heating and subsequent cooling. The results show that the residual deflection is primarily governed by the load level and the section shape and that the magnitude of the residual deflection can be even several times higher than the initial value.