1. Associate Professor, K. N. Toosi Univ., Mirdamad Ave. and Valiasr Ave., Tehran 19696, Iran.
2. Professor, Dept. of Civil Engineering, Univ. of British Columbia, 2324 Main Mall, Vancouver, BC, Canada, V6T 1Z4.
3. Graduate Student, Dept. of Civil Engineering, Univ. of British Columbia, 2324 Main Mall, Vancouver, BC, Canada, V6T 1Z4.