PSI - Issue 44

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2022) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 44 (2023) 1316–1323

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© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. The paper deals with the seismic retrofit of an existing monumental building through a hybrid solution, applying an isolation system to a previously strengthened and stiffened structure. The case study was built in the Central Italy in the middle of the 1960s. The building is a mixed steel-concrete structure with a plan extension of about 2000m 2 , with an inner decentralized open court. At the first level, it is characterized by R.C. pillars and two shear walls not symmetrically placed in the plan. Upon it, there are two other levels made of steel frames. The first-floor level is a “floating plane”: consisting of a grid of steel beams, it bears loads transferred from the upper components. Through it, a structural continuity is ensured between portions having different stiffness, i.e. a wide upper steel part more deformable than the small lower R.C: lower. Resulting from a gravity-load design approach, without taking into account seismic actions, this monumental building is highly irregular at each level, with a noticeable asymmetry due to the shear walls distribution. These R.C. elements are the only ones having a certain horizontal stiffness at the upper levels, where the existing slender steel bracings are not placed in correspondence to the lower pillars. In this case, a hybrid solution for seismic retrofitting has been proposed. Considering the high deformability of the steel elements, not bearing seismic forces, the preventive strengthening actions refer mainly to R.C. components, including the strengthening of the existing shear walls and the introduction of other two ones, the structural consolidation of the SAP-type slabs. In addition, the strengthening of the existing slender steel bracings is expected. Working on such stiffened structure, the isolation system introduces anti-seismic devices below the floating plane, using 32 HDRBs ( f 600) and 8 sliders. This solution increas s th fundamental v bration period from T FB = 0.563 s, valued for th fixed base, to T ISO = 3.05 s, for the strengthened isolated solution, reducing the seismic action of 76%. Keywords: seismic retrofit; hybrid solution; monumental strucutre; base isolation system; rubber devices; strucutral strenghtenin The paper deals with the seismic retrofit of an existing monumental building through a hybrid solution, applying an isolation system to a previously strengthened and stiffened structure. The case study was built in the Central Italy in the middle of the 1960s. The building is a mixed steel-concrete structure with a plan extension of about 2000m 2 , with an inner decentralized open court. At the first level, it is characterized by R.C. pillars and two shear walls not symmetrically placed in the plan. Upon it, there are two other levels made of steel frames. The first-floor level is a “floating plane”: consisting of a grid of steel beams, it bears loads transferred from the upper components. Through it, a structural continuity is ensured between portions having different stiffness, i.e. a wide upper steel part more deformable than the small lower R.C: lower. Resulting from a gravity-load design approach, without taking into account seismic actions, this monumental building is highly irregular at each level, with a noticeable asymmetry due to the shear walls distribution. These R.C. elements are the only ones having a certain horizontal stiffness at the upper levels, where the existing slender steel bracings are not placed in correspondence to the lower pillars. In this case, a hybrid solution for seismic retrofitting has been proposed. Considering the high deformability of the steel elements, not bearing seismic forces, the preventive strengthening actions refer mainly to R.C. components, including the strengthening of the existing shear walls and the introduction of other two ones, the structural consolidation of the SAP-type slabs. In addition, the strengthening of the existing slender steel bracings is expected. Working on such stiffened structure, the isolation system introduces anti-seismic devices below the floating plane, using 32 HDRBs ( f 600) and 8 sliders. This solution increases the fundamental vibration period from T FB = 0.563 s, valued for the fixed base, to T ISO = 3.05 s, for the strengthened isolated solution, reducing the seismic action of 76%. Keywords: seismi r trofit; hybrid solution; monum ntal strucutre; base isolation syst ; rubber d vices; strucutral strenghtenin XIX ANIDIS Conference, Seismic Engineering in Italy Seismic retrofit of an existing important building of the 60’s through a hybrid strategy Giuseppe Brandonisio a , Laura Giovanna Guidi a *, Davide Michelino a , Paola Sorrentino a , Antonello De Luca a a Dept. of Structures for Engineering and Architecture, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy XIX ANIDIS Conference, Seismic Engineering in Italy Seismic retrofit of an existing important building of the 60’s through a hybrid strategy Giuseppe Brandonisio a , Laura Giovanna Guidi a *, Davide Michelino a , Paola Sorrentino a , Antonello De Luca a a Dept. of Structures for Engineering and Architecture, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy Abstract Abstract

* Corresponding author. E-mail address: lauragiovanna.guidi@unina.it

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. 10.1016/j.prostr.2023.01.169 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy * Corresponding author. E-mail address: lauragiovanna.guidi@unina.it