1. Associate Professor, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Rio Grande do Sul 90035-190, Brazil (corresponding author).
2. Research Fellow, Federal Univ. of Rio Grande do Sul, Rio Grande do Sul 90035-190, Brazil.
3. Ph.D. Student, Federal Univ. of Rio Grande do Sul, Rio Grande do Sul 90035-190, Brazil.