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 2000m2, 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 TFB= 0.563 s, valued for the fixed base, to TISO= 3.05 s, for the strengthened isolated solution, reducing the seismic action of 76%.
Seismic retrofit of an existing important building of the 60's through a hybrid strategy / Brandonisio, G.; Guidi, L. G.; Michelino, D.; Sorrentino, P.; De Luca, A.. - In: PROCEDIA STRUCTURAL INTEGRITY. - ISSN 2452-3216. - 44:(2022), pp. 1316-1323. (Intervento presentato al convegno 19th ANIDIS Conference, Seismic Engineering in Italy tenutosi a ita nel 2022) [10.1016/j.prostr.2023.01.169].
Seismic retrofit of an existing important building of the 60's through a hybrid strategy
Brandonisio G.;Guidi L. G.;Sorrentino P.;De Luca A.
2022
Abstract
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 2000m2, 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 TFB= 0.563 s, valued for the fixed base, to TISO= 3.05 s, for the strengthened isolated solution, reducing the seismic action of 76%.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
