[1
]Research Assistant, Univ. of Minho, C-TAC Research Unit, 4800 Guimarães, Portugal
(corresponding author).
[2
]Associate Professor, Dept. of Civil Engineering, Univ. of Beira Interior, 6200 Covilhã,
Portugal.
[3
]Full Professor, Dept. of Civil Engineering, Univ. of Minho, 4800 Guimarães, Portugal.