1. Ph.D. Candidate, Division of Structural Engineering, Lund Univ., Box 118, 22100 Lund, Sweden (corresponding author).
2. Professor, Division of Structural Engineering, Lund Univ., Box 118, 22100 Lund, Sweden.
3. Professor Emeritus in Civil Engineering, Univ. of Texas at Austin, 10100 Burnet Rd., Building 177, Austin, TX 78758.