PSI - Issue 78

Emanuele Rizzi et al. / Procedia Structural Integrity 78 (2026) 1420–1427

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full-height columns aligned with the nave arcades. At the other end, the arcades terminate atthe triumphal arch, which separates the nave from the presbytery. The hall has varying heights: the central nave reaches a height of 15600 mm, while the two side aisles have a height of 9300 mm. The central nave is covered by a dual-pitched wooden structure built in the Lombard style. It has no ridge beam, but features primary beams arranged parallel to the eaves line, resting on trusses, with secondary joists laid along the roof slope. The side aisles feature single-pitched roofs, built using the same technique. The cross section of the rafters is 220 × 300 mm 2 (width × height). The roof supports additional dead loads from the full clay tiles used as underlayment and from the curved roof tiles, with surface weights of 0.54 kN/m² and 0.64 kN/m², respectively.

(a)

(b)

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Fig. 2. Main geometric characteristics of the case study: (a) plan dimensions of the nave in mm; (b) arcade and nave wall dimensions in mm; (c) columns section in mm. 3. Description of the intervention The intervention concerns the installation (Fig. 3), on the nave and the side aisles roofs, of an X-bracing system composed of steel tie rods made of stainless steel (type duplex 1.4462) positioned between the roof trusses. Moreover, a steel profile is connected along the top of the longitudinal walls, to resist the tensile forces generated by the bracing system, and an additional timber beam is installed at the rafter mid-span, to reduce the aspect ratio of the bracing system. The tie rods are pinned to steel gusset plates, which are bolted to the roof timber elements and to the steel profile. The strengthening system does not significantly increase the mass of the structure and acts as a horizontal diaphragm, improving the structural response by redistributing part of the seismic inertial forces from the nave walls to the outer walls under IP horizontal actions. Under OOP forces, it also provides restraint at the top of the nave walls against overturning, enhancing overall stability. By comparing the dynamic behavior of the church through finite element modal analysis before and after the intervention, it was determined that a cross-section of 707 mm² (corresponding to a circular section with a diameter of 30 mm) is sufficient to secure the global dynamic performance of the church.