1. Dept. of Civ. Engrg., King Fahd Univ. of Petroleum and Minerals, KFUPM Box 5058, Dhahran 31261, Saudi Arabia.
2. Sr. Res. Ofcr., Cranfield Univ., Royal Military Coll. of Sci., Engrg. Sys. Dept., Shrivenham, Swindon SN6 8LA, U.K. E-mail: r.a.barnes@ rmcs.cranfield.ac.uk
3. Prof. of Civ. Engrg., Cranfield Univ., Royal Military Coll. of Sci., Engrg. Sys. Dept., Shrivenham, Swindon SN6 8LA, U.K.