1. Assistant Professor, Civil Engineering Dept., King Saud Univ., P.O. Box 800, Riyadh, Saudi Arabia 1142111421 (on leave from Faculty of Engineering, Cairo Univ.) (corresponding author).
2. Graduate Student, Civil Engineering Dept., King Saud Univ., P.O. Box 800, Riyadh, Saudi Arabia 11421.
3. Professor, Civil Engineering Dept., King Saud Univ., P.O. Box 800, Riyadh, Saudi Arabia 11421.