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In this paper the lower bound theorem of limit analysis for No-Tension materials is applied to the equilibrium of spiral vaults, modeled as continuous unilateral membranes. The most efficient approach to the equilibrium of a thin shell is the covariant representation proposed by Pucher and adopted in the present study. Statically admissible singular stresses in the form of line or surface Dirac deltas and lying inside the masonry, are taken into account. The unilateral restrictions require that the Airy stress function representing the stress, be concave. The case study is a helical stair with a central pillar in Sanfelice Palace in Naples, whose structure is a tuff masonry spiral vault. The maps of the stress corresponding to two different stress functions and the safety factors in the two cases are provided

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In the past century, precast reinforced concrete has become the most widely used construction material in infrastructure engineering, especially for long-span structures. Nowadays, a growing research area concerns the assessment of concrete strength degradation due to environmental exposure and reinforcement corrosion. This paper reports an experimental campaign on some prefabricated concrete elements that were exposed to atmospheric agents for approximately 20 years. The campaign took the uncommon opportunity to access the full inspection and sampling of rebar. The included activities had different invasiveness and encompassed inspections, core sampling, corrosion potential mapping, compressive strength tests, as well as neutralization depth assays on cored surfaces, on chisel-split surfaces, and on drilling powders. The results bring together a global diagnostic picture of very limited degradation and of elements that are fully able to attend their design service life; the latter is estimated to be considerably higher than 20 years and to exceed 75 years if the concrete mix does not show quality issues. Results also permit drawing considerations on a hierarchy of diagnostic reliability in the evaluation of RC degradation, in which concrete core sampling plays the role of golden standard.

Recent earthquakes have shown the seismic vulnerability of the Italian Architectural heritage and the need of interventions. The restoration design should take into account not only assessment and rehabilitation, but also the need of fruition of the cultural assets. These aspects have been considered in the last Italian seismic codes, a performance-based set of technical requirements to be addressed in the design process. In this framework, the requirements that the materials, meant to repair or replace historic ones, should fulfill are a key issue. In particular, for tuff masonry structures, the evaluation of the mechanical characteristics of the mortar is essential. Tests performed directly on samples withdrawn on site are perhaps the most reliable tools to determine the strength characteristics of a mortar to be used for restoration. Unfortunately, the possible dimensions of the samples are not compatible with the minimum required for a reliable mechanical test, so that the characterization of the old mortars and their historic context can be made obtaining information by the treatises of the time: components and their proportions, together with curing operations are often reported in the manuals. In particular, in the Middle Age the Roman knowledge about pozzolanic mortars was somewhat lost, and the results can be seen in the durability problems of several monuments of the period. These last considerations are the motivations of this paper, in which a study of the pozzolanic mortars in tuff masonry structures is provided. As a case study, the tuff masonry structures of the Paleocristian Basilica in Cimitile are considered and examined.