1. Thomas and Laura Hsu Professor and Chair, Dept. of Civil and Environmental Engineering, Cullen College of Engineering, Univ. of Houston, N127 Engineering Bldg. 1, Houston, TX 77204-4003.
2. Professor, Dept. of Civil, Environmental, Aerospace and Material Engineering, Univ. of Palermo, Viale delle Scienze Edificio 8, 90128 Palermo, Italy.
3. Associate Professor, Dept. of Civil, Environmental, and Geo-Engineering, Univ. of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455-0116.
4. Research Fellow, Dept. of Civil, Environmental, Aerospace and Material Engineering, Univ. of Palermo, Viale delle Scienze Edificio 8, 90128 Palermo, Italy (corresponding author).