1. Professor, Dept. of Mechanical Engineering, Federal Univ. of Rio Grande do Sul, Av. Sarmento Leite 425, CEP 90050-170, Porto Alegre, RS, Brazil (corresponding author).
2. Professor, Dept. of Civil Engineering, Federal Univ. of Rio Grande do Sul, Av. Osvaldo Aranha 99, CEP 90035-190, Porto Alegre, RS, Brazil.
3. Professor, Dept. of Mechanical Engineering, Federal Univ. of Rio Grande do Sul, Av. Sarmento Leite 425, CEP 90050-170, Porto Alegre, RS, Brazil.
4. Research Assistant, Dept. of Civil Engineering, National Univ. of Tucumán, Av. Independencia 1800, CP 4000, San Miguel de Tucumán, Tucumán, Argentina.