1. Leader, Structures Group, Engineering Laboratory, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8611, Gaithersburg, MD 20899-8611.
2. Research Structural Engineer, Engineering Laboratory, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8611, Gaithersburg, MD 20899-8611 (corresponding author).
3. Senior Research Structural Engineer, Engineering Laboratory, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8611, Gaithersburg, MD 20899-8611.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125.