1. Research Assistant, Dept. of Civil Engineering, Case Western Reserve Univ., 10900 Euclid Ave., Cleveland, OH 44106-7201.
2. Frank H. Neff Professor, Dept. of Civil Engineering, Case Western Reserve Univ., 10900 Euclid Ave., Cleveland, OH 44106-7201 (corresponding author).
3. Research Scientist, NASA Glenn Research Center, 21000 BrookPark Rd., Cleveland, OH 44135.