1. Associate Professor, Federal Univ. of Ouro Preto, Dept. of Mines Engineering, Campus Universitário, Ouro Preto, MG, Brazil, 35400-000 (corresponding author).
2. Titular Professor, Federal Univ. of Viçosa, Dept. of Civil Engineering, Campus Universitário, Viçosa, MG, Brazil, 36570-000.
3. Fluor Centennial Associate Professor, Univ. of Texas at Austin, Dept. of Civil Engineering, 1 University Station C1792, Austin, TX 78712-0280.