1. Assistant Professor, Dept. of Civil and Architectural Engineering, Sultan Qaboos Univ., P.O. Box 33, Al-Khod, Muscat 123, Sultanate of Oman (corresponding author).
2. Professor, Dept. of Civil Engineering, Univ. of Engineering and Technology, Taxila, Pakistan.
3. Professor, Dept. of Civil Engineering, Tohoku Univ., Sendai, Japan.