1. Postdoctoral Scholar, Dept. of Structural Engineering, Univ. of California, San Diego, La Jolla, CA 92093-0085; formerly, JSPS Research Fellow, Dept. of Urban and Civil Engineering, Ibaraki Univ., Nakanarusawa 4-12-1, Hitachi 316-8511, Japan (corresponding author).or
2. Professor, Dept. of Urban and Civil Engineering, Ibaraki Univ., Nakanarusawa 4-12-1, Hitachi 316-8511, Japan.