1. Res., Dept. of Struct. Anal. and Des., Univ. of Naples Federico II, Naples, Italy. E-mail: demattei@unina.it
2. PhD, Norsk Hydro Tech. and Proj. Div., Light Metal Products N-0246 Oslo, Norway.
3. Prof., Dept. of Struct. Engrg., Norwegian Univ. of Sci. and Technol. (NTNU), 7034 Trondheim, Norway.
4. Prof., DSSAR, Univ. of Chieti, Pescara, Italy.