PSI - Issue 78

Elisabetta Bersanetti et al. / Procedia Structural Integrity 78 (2026) 372–378

377

-102323

-65678

176

MEAN

SLIDERS

N - Seismic

N - Static

Displacement

Maximum Values and Mean Values

(kg)

(kg)

mm 208 170

-667326 -148753

-469257 -114539

MAX

MEAN

The next step in the design process involved the following evaluations. The superstructure have to be verified considering only elastic behavior, so through linear analyses for both in-plane and out of-plane seismic actions. Due to the adoption of the base isolation system, the masonry structure is subjected at SLV (Life Limit State) to a reduced seismic demand of Sd (T = 2.89) = 0.048g, compared to the pre-intervention value of Sd (T = 0.7) = 0.33g, indicating a significant reduction in seismic forces (see Fig.4). To achieve the 80% seismic compliance target, only limited reinforcement was required for the masonry elements, restricted to small peripheral zones of the building. These include the interface areas between reinforced concrete and masonry structures, where bonding was ensured, and the upper stories where the compressive stress in the masonry is lower. For the design of beams to be placed below the existing floor slab between the basement and ground floor, responsible for transferring the masonry loads to the isolation devices, it was deemed more effective to construct a system of concrete beams. This solution was adopted due to the substantial thickness of the masonry walls to be supported (ranging from 50 to 80 cm), and to minimize potential vertical deformations. At the underside of the floor slab, the concrete beam system is complemented by a steel frame system to ensure horizontal stiffness of the diaphragm above the isolators.

Fig.7 Complete beam system (concrete and steel ones). Red color for bond beams on masonry, under isolators, and blue color for beams over isolators, to support building elevation.

Fig.8 Typological section of isolation system. Red color for bond beams on masonry, under isolators, and blue color for beams over isolators, to support building elevation.

The structural design also included checks of the substructure in the elastic range (q = 1,0). A concrete ring beam was proposed atop the masonry walls to serve as the support surface for the devices and ensure optimal distribution of concentrated loads. The existing masonry walls beneath were strengthened through widespread jacketing using fiberglass mesh, and a continuous concrete