this special issue comprises selected papers presented at the XXV edition of“Italian Steel Days” held in Salerno on October 1-2, 2015. This conference represents the place where Italian researchers present their results and development activities in the field of Steel Structures. Common papers’ emphasis is about the structural performance under seismic conditions. Due to the number of selected papers, in addition to the current issue, a second one is in preparation. The Guest Editors, Rosario Montuori and Francesco Fabbrocino, wishes to thank Dr. Gianmario Benzoni for this opportunity and for his assistance.