Why Fracture Mechanics?
Fracture mechanics is a failure theory that
1. determines material failure by energy criteria, possibly in conjunction with strength (or yield) criteria, and
2. considers failure to be propagating throughout the structure rather than simultaneous throughout the entire failure zone or surface.
While fracture mechanics has already been generally accepted in failure analysis of metal structures, especially in aerospace, naval, and nuclear engineering, its advent in the field of concrete structures is new. Therefore, after briefly outlining the history of this discipline, we will attempt in this introductory chapter to spell out the reasons for adopting the fracture mechanics approach and will focus especially on the structural size effect – the main reason for introducing fracture mechanics into the design of concrete structures.