1. Member, ASCE
2. Consultant, #5493 Wildwood Cr., Delta (Tsawwassen), BC, Canada V4M 3S8.
3. Prof., Dept. of Civ. and Envir. Engrg., Univ. of Alberta, Edmonton, AB, Canada T6G 2G7 (corresponding author). E-mail: dcsego@civil. ualberta.ca
4. Prof., Dept. of Civ. and Envir. Engrg., Univ. of Alberta, Edmonton, AB, Canada T6G 2G7.