PSI - Issue 64

Sabatino Di Benedetto et al. / Procedia Structural Integrity 64 (2024) 983–990 S. Di Benedetto / Structural Integrity Procedia 00 (2019) 000 – 000

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Nomenclature CBFs Concentrically Braced Frames (CBFs) G k1 Structural loads G k2 Non-structural loads Q k Variable loads DL Damage Limitation Limit State LS Life Safety Limit State ULS Ultimate Limit State D/C Demand over Capacity ratio PGA C Peak Ground Acceleration (Capacity) PGA D Peak Ground Acceleration (Demand) S pa,LS

Pseudo-acceleration at the Life Safety Limit State Pseudo-acceleration at the Damage Limitation Limit State

S pa,DL

Seismic risk index Overstrength factor

 E  ov

Ratio between the resistance and design value of the axial force in the brace



N pl,Rd,i Plastic axial resistance of a given brace i N Ed,E,i, Design axial force of a given brace i N Ed,G

Axial force in the column in the gravity combination Shear force in the column in the gravity combination Bending moment in the column in the gravity combination Axial force in the column in the seismic combination Shear force in the column in the seismic combination Bending moment in the column in the seismic combination

V Ed,G M Ed,G N Ed,E V Ed,E M Ed,E

1. Introduction Statistics from the ISTAT census data (2001) and the CARTIS database (Zuccaro et al., 2023) reveal that masonry and reinforced concrete buildings dominate the Italian architectural landscape, accounting for approximately 90% of all structures. Conversely, steel buildings constitute a minor fraction, primarily found in industrial (Cantisani and Della Corte, 2022; Mazzolani et al., 2022; Tartaglia et al., 2022) and strategic facilities (Milone et al., 2022; Milone, 2023), often erected prior to the implementation of seismic codes and primarily designed to withstand wind loads. Consequently, there is a pressing need to assess the seismic performance of these existing structures and to develop suitable retrofitting strategies. In this context, the present study aims to assess the seismic response of a school placed in Avellino, Italy, and characterised by steel structural frames. The necessity for this investigation stems from the fact that the structure was erected in the early 1980s, a time when Italian design standards primarily addressed gravitational and wind forces, with seismic rules being less stringent. The seismic assessment at the time was based on less rigorous criteria compared to current standards. Therefore, a re-evaluation of the school's seismic performance is warranted. The building features CBFs for lateral resistance and pinned frames to support gravitational loads. The seismic analysis revealed the inadequacy of the existing bracings to withstand seismic forces. Consequently, the study proposes the implementation of innovative anti-seismic devices with a metal foam core to reinforce the braces and enhance the school's seismic resilience. Specifically, these devices activate when tension forces act upon the bracings, converting them into compressive forces within the metal foam core, thus providing increased resistance. The design concept draws inspiration from the investigations carried out by Moradi (2011) and Moradi and Arwade (2014), with recent enhancements validated through experimental tests, numerical simulations, and analytical studies conducted at the University of Salerno, University of Naples Federico II, and the Nagoya Institute of Technology (de la Peña et al., 2023).