1. Ph.D. Candidate, Dept. of Civil Engineering, Univ. of Coimbra, 3030-788 Coimbra, Portugal (corresponding author).
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Coimbra, 3030-788 Coimbra, Portugal.
3. Lecturer, Dept. of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, U.K.