1. Dept. of Civil Engineering, 362D Whittier Research Center, Univ. of Nebraska, Lincoln, NE 68583 US, e-mail: gabriron01@huskers.unl.edu
2. Dept. of Civil Engineering, 362H Whittier Research Center, Univ. of Nebraska, Lincoln, NE 68583 US, e-mail: tyou2@unl.edu
3. Dept. of Civil Engineering, 362N Whittier Research Center, University of Nebraska, Lincoln, Nebraska 68583 US (Corresponding author), e-mail: ykim3@unl.edu