1. Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
2. Department of Civil, Architectural, and Environmental Engineering, The University of Texas at Austin, 1 University Station C1752, Austin, TX 78712-0273, USA.
3. Department of Civil Engineering, 151C Raymond Building, University of Kentucky, Lexington, KY 40506-0281, USA.