1. Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, P. O. Box 55136-553, Iran
2. Department of Civil Engineering, Marand Branch, Islamic Azad University, Marand, Iran
3. Department of Civil and Environmental Engineering, University of Pittsburgh, 3700 O’ Hara Street, 729 Benedum Hall, Pittsburgh, PA 15261, USA