1. Assistant Professor, Dept. of Civil Engineering, National Taiwan Univ., Taipei City, Taiwan (corresponding author); formerly, Assistant Professor, School of Civil and Environmental Engineering, Nanyang Technological Univ., Singapore 639798.
2. Professor, Dept. of Civil, Structural and Environmental Engineering, State Univ. of New York at Buffalo, Buffalo, NY 14260.
3. Research Structural Engineer, U.S. Geological Survey, Box 25046-DFC-MS 966, Denver, CO 80225. E-mail: nluco@usgs.gov
4. Senior Principal, Simpson Gumpertz & Heger Inc., The Landmark at One Market, Ste. 600, San Francisco, CA 94105. E-mail: rohamburger@sgh.com