1. Exponent, Failure Analysis Associates, Menlo Park, CA 94025. E-mail: puriz@exponent.com
2. Civil and Environmental Engineering, Univ. of California, Berkeley, CA 94720. E-mail: filippou@ce.berkeley.edu
3. Civil and Environmental Engineering, Univ. of California, Berkeley, CA 94720. E-mail: mahin@ce.berkeley.edu