Non-destructive methods applied for in situ mechanical diagnosis: Florentine historical buildings in Pietra Serena

Abstract

Uniaxial Compressive Strength (UCS) is a key indicator of the mechanical properties of a rock, particularly in the diagnostic and restoration phases when stones are employed as construction material. In historical buildings, it is important to determine UCS values without utilizing tests that involve destructive rock sampling. To estimate UCS, non-destructive techniques, such as ultrasonic pulse velocity (Vp) and Schmidt hammer tests (R), can be combined to provide a useful tool. However, for architectural elements with complex morphology, it is sometimes impossible to perform both ultrasonic and sclerometric test. Three different UCS predictive models, one using R only, one using Vp and one using both, have been developed through regression techniques on a dataset comprising 45 Pietra Serena sandstone samples with varying levels of decay. The models were tested for their performance through Cross-Validation techniques and were then applied to a dataset of Vp and R values measured in situ on Pietra Serena corbels of balconies belonging to historical buildings in Florence (Italy). The specific predictive models were applied to real case studies, and the UCS of the rocks used in historical buildings was calculated, enabling the definition of the mechanical characteristics of building elements belonging to an important cultural context, Florentine historical architecture, without using destructive testing.