1. Dept. of Civil and Environmental Engineering, Lehigh Univ., Bethlehem, PA 18015; presently, Dept. of Civil and EnvironmentalEngineering, National Univ. of Kaohsiung, Kaohsiung, Taiwan, ROC.
2. Professor, Dept. of Civil and Environmental Engineering, Lehigh Univ., Bethlehem, PA 18015 (corresponding author). E-mail: wez3@lehigh.edu