ESTIMATION OF THE RESIDUAL STIFFNESSES OF FIRE-DAMAGED CONCRETER MEMBERS

The residual stiffness of concrete after exposure to fire is a very important issue for the load-carrying capacity assessment and seismic analysis of fire-damaged concrete structures. It is also one of the most important criterions of repairing and reinforcing fire-damaged concrete structures. Based on the equivalent elastic modulus method, improved sub-section model method and inverse method developed in this paper, the residual stiffness of fire-damaged concrete members are estimated. The effects of fire duration time, steel ratio and sectional dimensions on the stiffness are presented in detail. The results of examples show that the three methods developed in this paper can accurately and conveniently estimate the residual stiffness of fire-damaged concrete members.