The service involved a Vulnerability Assessment and PFTE for static and seismic consolidation, including the determination of the necessary cost for the reuse of this complex as the headquarters for the Police Headquarters and State Police of Massa Carrara. It is located in the city center of Massa and consists of two buildings totaling 15,000 sq m. The main building, named “A/B,” was constructed by the Bank of Italy in the 1960s as its headquarters (though partly intended for residential use), based on a design by Prof. Arch. Giulio Roisecco. The building, considered a significant example of modern architecture and widely referenced in literature, is subject to urban planning protection by the Municipality through “the inadmissibility of any modification to facades and other exterior works. Internal works are permitted provided they are of limited scope and do not alter valuable structural components or recognizability.” The other building, named “C,” is coeval but of lesser value and was acquired by the Bank in 1976.
Historical and Documentary Analysis
Due to the age of construction of the two buildings, and especially the significance of the main building—both for the caliber of the Client and the renown of the Designer—it was deemed possible, from the outset of the service, to obtain the original design documents. This is indeed what occurred.
The Investigations
The campaign of instrumental investigations was entrusted to a Laboratory equipped not only with ministerial authorization as per Art. 59 DPR 380/01 and Art. 20 L. 1086/71, but also with specific qualifications for testing and inspecting construction materials of existing structures and buildings, in accordance with the most recent Circular 03.1.2019, no. 633/STC. Visual inspections of construction details were carried out by SB+ engineers, supported by the construction company that performed plaster removal, restorations, and, more generally, all necessary assistance (providing ladders and scaffolding, opening false ceilings, etc.). A total of over 600 investigations, both visual and instrumental, were conducted.
Geognostics
Thanks to existing knowledge and new investigations (geognostic and geo-seismic), it was possible to reconstruct the subsurface geometries, divide it into lithotechnical units, and characterize it in terms of its main seismic parameters. The soil category identified in the seismic survey (MASW+REMI+HVSR) allowed this soil to be classified as type B using the simplified approach. From a geotechnical perspective, sufficient geomechanical parameters were found. The liquefaction analysis proved the absence of this risk, as the superficial lithologies only partially fall within liquefiable types, and no water tables are present in the first tens of meters of the subsurface.
The Modeling
The building analysis, performed using the FEM method, was carried out by defining three-dimensional models with Sismicad 12.20 software. The structural modeling first involved creating a seismic joint in the main building to allow independent seismic behavior between the lower (A) and upper (B) parts. Foundations, also placed at different levels, were then modeled, all resting on elastic Winkler soil, along with vertical elements (reinforced concrete columns and walls) and horizontal structures consisting of floor slabs and their respective floor beams. The effect of horizontal force misalignment, induced for example by floor torsion, was also considered by simulating it through the introduction of additional planar eccentricities, which constitute further elementary load conditions to be accumulated and combined according to the criteria of the previous paragraph. Stresses on members are evaluated based on the following assumptions and methods:
- Beams and columns deformable under normal stress, biaxial bending, biaxial shear, and torsional moment. Reduction coefficients for moments of inertia were included to account for the reduction in flexural and torsional stiffness due to concrete cracking. A multiplier for the axial stiffness of columns was included to approximately account for column shortening due to normal stress during construction;
- Foundation beams on Winkler soil are solved in closed form using a specific finite element. Reinforced concrete walls are analyzed by schematizing them as slab-plate elements discretized with a maximum step assigned during data input;
- Footings on Winkler soil were modeled with the introduction of elastoplastic vertical springs;
- Piles were modeled by subdividing the shaft into multiple segments immersed in soils with stratigraphy defined based on the geognostic investigations performed;
- Plates were discretized into a finite number of slab-plate elements with a maximum step assigned during data input; in the case of foundation rafts, nodes are connected to the soil by springs with vertical translational stiffness and, if required, horizontal stiffness;
- The calculation of seismic effects was conducted with modal dynamic analysis in accordance with the various adopted regulations;
The Verifications
Regarding static actions, no deficiencies emerged concerning ultimate limit state (ULS) verifications for either main members or intermediate and roof floor structures. Seismic analyses, however, revealed deficiencies concerning life safety limit state (SLV) verifications. The elements with the most significant deficiencies are beams and columns due to material properties on the concrete side, and, particularly for beams, due to insufficient positive moment reinforcement near the columns. The level of protection resulting from the study was then indicated as differentiated for each structural unit: 37% for Body A, 11% for Body B, and 8% for Body C.
The Interventions
The proposed interventions consisted of:
- beam reinforcement using CFRP fibers;
- beam reinforcement using pultruded carbon laminates;
- reinforced concrete wall reinforcement using CFRP fibers;
- reinforced concrete column jacketing using fiber-reinforced cementitious mortar with very high mechanical performance;
anti-overturning bracing of infill panels using CFRP fibers.
