Determination of Residual Crack Extension Resistance of Post fire Concrete by Weight Function Method

Abstract:

The residual crack extension resistance curves (KR(Δa) curves) of post fire concrete, associated with cohesive force distribution on fictitious crack zone of complete fracture process, were obtained by analytical method and weight function method. Wedge splitting tests of 10 groups at temperatures from 20 °C to 600 °C were made. The cohesive force distribution corresponding to four different crack propagation stages was determined according to Petersson and CEB FIP Model 1990 bi linear softening traction separation law. It is found that the residual fracture toughness increases with the increasing of the crack length, whereas, the KR(Δa) curves decrease with the increasing temperatures for the thermal damage induced. KR(Δa) curves calculated by analytical and weight function method have a good coincidence. The softening curves have an obvious influence on the shape of KR(Δa) curves.

Key words:wedge splitting method; post fire; weight function; softening traction separation curves; crack extension resistance curves