1. Postdoctoral Fellow, Dept. of Civil and Environmental Engineering, Univ. of Waterloo, 200 University Ave. West, Waterloo, ON, Canada N2L 3G1 (corresponding author).
2. President, Bolton Photosciences Inc., 628 Cheriton Cres., NW, Edmonton, AB, Canada T6R 2M5.
3. Professor, Dept. of Civil Engineering, Univ. of Toronto, 35. St. George St., Toronto, ON, Canada M5S 1A4.
4. Associate Professor, Dept. of Civil Engineering, Univ. of Toronto, 35. St. George St., Toronto, ON, Canada M5S 1A4.