1. Civil Engineer, Assystem France, Energy and Nuclear Division, CEA Cadarache, Bat 784, 13108 St-Paul-Lez-Durance, Cedex, France.
2. Professor, Dept. of Civil, Geological and Mining Engineering, Ecole Polytechnique de Montreal, Montreal Univ. Campus, P.O. Box 6079, Station CV, Montreal, P.Q, Canada H3C 3A7 (corresponding author).