P. Roccaro, C. Barone, G. Mancini, F.G.A. Vagliasindi*
Department of Civil and Environmental Engineering, University of Catania, Italy
Tel. +39 (095) 7382704; Fax +39 (095) 7382748; email: fvaglias@dica.unict.it
Received 2 December 2005; revised 28 March 2006 accepted; 11 May 2006