1. Research Assistant, Dept. of Civil Engineering, Univ. of Waterloo, Ontario, Canada N2L 3G1.
2. Canada Research Chair Professor, Dept. of Civil Engineering, Univ. of Waterloo, Ontario, Canada N2L 3G1 (corresponding author). E-mail: soudki@uwaterloo.ca
3. Vice President, Halsall Associates Limited, Toronto, Ontario, Canada M4P 1E4.