Analysis of concrete structures by fracture mechanics : proceedings of the International RILEM Workshop dedicated to Professor Arne Hillerborg / per Elfgren, L., Shah, S. P., RILEM (The Internatinal Union of Testing and Research Laboratories for Materials and Structures), RILEM Technical Committee 90-FMA Fracture Mechanics of Concrete Structures-Applications, International Rilem Workshop on Fracture Mechanics of Concrete Structures (1989 : Abisko, Sewden)