1. Graduate Student, Dept. of Civil Engineering and Applied Mechanics, McGill Univ., Room 492, Macdonald Engineering Bldg., 817 Sherbrooke St. West, Montreal PQ, Canada H3A 2K6.
2. William Scott Professor and James McGill Professor, Dept. of Civil Engineering and Applied Mechanics, McGill Univ., Rm. 492, Macdonald Engineering Bldg., 817 Sherbrooke St. West, Montreal PQ, Canada H3A 2K6.