1. Associate Professor, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Brazil (corresponding author).
2. Associate Professor, Faculty of Engineering, Univ. of Porto, Portugal.
3. Research Fellow, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Brazil. E-mail: rccaberlon@hotmail.com
4. Ph.D. Student, Faculty of Engineering, Univ. of Porto, Portugal.