1. Dept. of Civil and Environmental Engineering, Univ. of Brasilia, SG-12 Bldg., Asa Norte, Federal District, Brasília 70910-900, Brazil.
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Brasilia, SG-12 Bldg., Asa Norte, Federal District, Brasília 70910-900, Brazil.