PSI - Issue 78

Michele Angiolilli et al. / Procedia Structural Integrity 78 (2026) 1807–1814

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Fig. 1. Construction phases: a) installation of steel rebars for the reinforced concrete foundation; b) placement of the electrical insulation system over the resined foundation; c) installation of the cryostat support beam at the base; d) vertical assembly of the structure; e–f) installation of the steel membrane panels; g) placement of the support bracket device

nominal design life of the structure was assumed to be 50 years, and, as it is classified as Use Class IV—required by regional regulations for all structures within LNGS and corresponding to buildings of strategic importance—a reference seismic life of 100 years was adopted. Moreover, the structure was designed at the Life Safety Limit State – SLV, according to NTC18 (2018) – using a low ductility class and assuming a behavior factor q = 1.5 Finally, a range of auxiliary infrastructure has been designed and are being constructed in Hall C to support the experiment, such as the 4-floor cryogenic support structure for piping and equipment, the access structure connecting the cryostat top to the support structure levels, a protective covering structure, and a future 3-floor building housing the control and counting rooms. The so-called cold structure of the DS-20k cryostat consists of multiple layers of insulation including plywood, reinforced polyurethane foam, a membrane of composite laminated material (i.e., the secondary membrane) and an innermost corrugated stainless steel membrane, 1.2mm thick (i.e., the primary membrane), which will be in direct contact with LAr and, thanks to its corrugation ensure high elasticity and capability for deformation during cool down. This insulation and containment system is based on the membrane technology developed by Gaztransport & Technigaz (GTT), a global leader in cryogenic storage solutions primarily used for liquefied natural gas. For the DS 20k application, thermal specifications require a minimum overall insulation thickness of 800 mm, integrating both the primary and secondary membranes to ensure reliable liquid containment at cryogenic temperatures, and an equivalent load of 100 kg / m 2 was considered for the structural design. Note that the roof of the cryostat consists of five modules, or top caps: a central square module, two long modules, and two short modules. For these elements, the insulation system was preassembled outside LNGS, fixed to the I-beam system, and then shipped to LNGS as five complete units. Fig. 2.a shows one of the final stages of the installation, 2.2. Insulation and cryostat cold membrane