1. Postdoctoral Fellow, Dept. of Civil, Architectural, and Environmental Engineering, Univ. of Texas at Austin, 1 University Station C1752, Austin, TX 78712-0276. E-mail: uniastro@mail.utexas.edu
2. Professor, Dept. of Civil Engineering, Univ. of Waterloo, 200 University Ave. West, Waterloo ON, Canada N2L 3G1. E-mail: chaas@civmail.uwaterloo.ca
3. Assistant Professor, Dept. of Civil, Architectural, and Environmental Engineering, Univ. of Texas at Austin, 1 University Station C1752, Austin, TX 78712-0276 (corresponding author). E-mail: caldas@mail.utexas.edu