Fracture mechanics of concrete: Will applications start to emerge?

Fracture mechanics of concrete has developed into an active field of research in the past decades. It promises a rational solution technique to structural problems in reinforced concrete in the limit state. Numerical tools have been developed on the basis of fracture mechanics theories. The question to be addressed is how much of the early promise, i.e. the promise of a powerful rational numerical tool having predictive capabilities, has come true, and whether additional research is needed in order to further extend the range of applicability of the new tools. Essential for new applications, both at the structural and the materials engineering level seems a combined experimental and numerical approach. Both experimentation and numerical simulation have grown to a level where highly advanced techniques are applied, often too complex and of a scope too wide to be comprehended by a single researcher. Structural engineering applications of fracture mechanics must be sought in problems where the concrete reaches its limit state, and where knowledge of softening becomes eminent. Examples are the minimum reinforcement ratio in reinforced concrete structures, or structural details like anchor pull-out. Other recent developments point towards applications at the material level, where numerical models at the meso-level (particle level) of the concrete are used to develop materials for specific structural applications. At best numerical analyses and testing should be carried out in dose cooperation. A meaningful development seems one where the softening response of the material (for example by adding fibres to increase the ductility) is optimised in conjunction with new structural applications. The development of a SKFCON truss systems is a recent example