1. Assistant Professor, Dept. of Civil Engineering, College of Engineering, King Saud Univ., Riyadh, P.O. Box 800, Riyadh, Saudi Arabia 11421.
2. Professor, Structural Engineering, Dept. of Civil Engineering; Managing Director, Center of Excellence for Concrete Research and Testing, College of Engineering, King Saud Univ., Riyadh, P.O. Box 800, Riyadh, Saudi Arabia 11421 (corresponding author).