1. Design Engineer, Buckland & Taylor, Ltd., 101-788 Harbourside Dr., North Vancouver BC, Canada V7P 3R7.
2. Assistant Professor, Dept. of Civil Engineering, Univ. of British Columbia, 6250 Applied Science Lane, Vancouver BC, Canada V6T 1Z4 (corresponding author). E-mail: elwood@civil.ubc.ca
3. Assistant Professor, Dept. of Civil Engineering, Univ. of British Columbia, 6250 Applied Science Lane, Vancouver BC, Canada V6T 1Z4.