1. Associate Professor, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Ave. Osvaldo Aranha, 99, 3. andar, 90035-190 Porto Alegre, Rio Grande do Sul, Brazil (corresponding author).
2. Research Assistant, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Ave. Osvaldo Aranha, 99, 3. andar, 90035-190 Porto Alegre, Rio Grande do Sul, Brazil.
3. Associate Professor, School of Engineering and Architecture, Catholic Univ. of Pelotas, Rua Félix da Cunha, 412, 96010-000 Pelotas, Rio Grande do Sul, Brazil.
4. Associate Professor, School of Engineering, Univ. of Passo Fundo Campus I, Bairro São José, 99001-970 Passo Fundo, Rio Grande do Sul, Brazil.