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