Fracture Mechanics Assessment of Beam-to-Column Joints Subjected to Cyclic and Dynamic Loading

With a lesson learned from the Kobe Great Earthquake, an engineering method, WES 2808, has been developed in Japan for evaluating the structural integrity under the seismic condition. This paper presents a method for fracture mechanics assessment of beam-to-column joints subjected to cyclic and dynamic loading on the basis of WES 2808. WES 2808 includes two key ideas. One is a reference temperature concept for fracture toughness evaluation. The material fracture toughness under the seismic condition is replaced by the static fracture toughness without pre-strain at a reference temperature of T−ΔTpd, where T and ΔTpd are the service temperature and the temperature shift of the fracture toughness by pre-strain and dynamic loading, respectively. ΔTpd is given as a function of the flow stress elevation in the seismic condition. Another idea is a correction of constraint loss in structural components. A large amount of plastic deformation causes a loss of plastic constraint in structural components. In order to account for the constraint loss in the fracture assessment of components, the equivalent CTOD ratio β = δ3p / δStruc. is implemented, where δ3p and δStruc. are CTODs of the fracture toughness specimen and the structural component, respectively, at the same level of the Weibull stress.