1. Asst. Prof., Dept. of Civ. Engrg., Shiraz Univ., Shiraz, Iran
2. Assoc. Prof., Dept. of Civ. and Envir. Engrg., Michigan State Univ., East Lansing, MI 48824 (corresponding author). E-mail: wallace@ egr.msu.edu
3. Visiting Asst. Prof., Dept. of Civ. and Envir. Engrg., Michigan State Univ., East Lansing, MI 48824.
4. Prof., Dept. of Crop and Soil Sci., Michigan State Univ., East Lansing, MI 48824.
5. Prof., Dept. of Civ. and Envir. Engrg., Michigan State Univ., East Lansing, MI 48824.