1. L. B. Ryon Endowed Chair in Engineering, Rice Univ., Houston, TX 77251.
2. Assistant Professor, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 S.W. Mudd Bldg., 500 W. 120th St., New York, NY 10027 (corresponding author).
3. Ph.D. Student, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 S.W. Mudd Bldg., 500 W. 120th St., New York, NY 10027.
4. Associate Professor, Dept. of Structural Engineering, Univ. of São Paulo, Avenida Trabalhador São-Carlense, No. 400, Centro, CEP 13566-590, São Carlos, São Paulo, Brazil.