1. Assistant Professor, Dept. of Civil Engineering, W351 Nebraska Hall, Univ. of Nebraska, Lincoln, NE 68588-0531 (corresponding author). E-mail: ykim3@unl.edu
2. Professor, Dept. of Engineering Mechanics, 114 Othmer Hall, Univ. of Nebraska, Lincoln, NE 68588-0642. E-mail: dhallen@unlnotes.unl.edu
3. Professor, Dept. of Civil Engineering, 601 CE/TTI Building, Texas A&M Univ., College Station, TX 77843-3135. E-mail: d-little@tamu.edu