1. Ph.D. Student, Dept. of Civil Engineering, ISISE, Univ. of Minho, Azurém, 4800-058 Guimarães, Portugal.
2. Assistant Professor, Dept. of Civil Engineering, ISISE, Univ. of Minho, Azurém, 4800-058 Guimarães, Portugal.
3. Professor, Dept. of Civil Engineering, ISISE, Univ. of Minho, Azurém, 4800-058 Guimarães, Portugal.