1. Professor, Dept. of Civil, Geological, and Mining Engineering, Ecole Polytechnique de Montreal, Montreal Univ. Campus, P.O. Box 6079, Station CV, Montreal PQ, Canada H3C 3A7 (corresponding author). E-mail: pierre.leger@polymtl.ca
2. Research Engineer, Dept. of Civil, Geological, and Mining Engineering, Ecole Polytechnique de Montreal, Montreal Univ. Campus, P.O. Box 6079, Station CV, Montreal PQ, Canada H3C 3A7.