1. Senior Research and Development Engineer, Machine Research, Caterpillar Inc., Mossville, IL 61552.
2. Joint Assistant Professor, Dept. of Civil and Environmental Engineering, 3505C CEBA Building, Louisiana State Univ. and Southern Univ., Baton Rouge, LA 70803 (corresponding author).
3. Boyd Professor, Dept. of Civil and Environmental Engineering, 3508B CEBA Building, Louisiana State Univ., Baton Rouge, LA 70803.