1. Graduate Research Assistant, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE 68182-0178.
2. Graduate Research Assistant, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Lincoln, NE 68588-6105.
3. Associate Professor, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE, 68182-0178.
4. Associate Professor, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE, 68182-0178 (corresponding author).