1. Lect., Dept. of Civ. Engrg., Liverpool Univ., Liverpool L69 3GQ, U.K. (corresponding author). E-mail: ttanyi@liv.ac.uk
2. Asst. Prof., Civ. Engrg. Dept., Univ. of Tehran, P.O. Box 14155-6457, Tehran, Iran.
3. Prof., Dept. of Civ. Engrg., Univ. of Liverpool, Liverpool L69 3GQ, U.K. E-mail: r.burrows@liv.ac.uk