1. a Civil Engineering Department , Institute Superior Tícnico , Av. Rovisco Pais, 1049-001, Lisbon, Portugal E-mail:
2. b Civil and Environmental Engineering Department , Imperial College of Science, Technology and Medicine , Imperial College Road, SW7 2BU, London, UK E-mail:
3. c Polymer Engineering Department , Minho University , Azurém Campus, 4800-058, Guimaraes, Portugal E-mail: