Dynamic identification of the tabernacle of the church of Santa Maria Maggiore in Spello, Italy

Abstract

The conservation of architectural heritage is a primary concern for the preservation of the cultural identity of a population and of the tangible proofs of historic architectural development. Architectural artifacts must be protected over time from all the threats that could derive by both the variation of inherent properties, as the aging of the constituent materials, and external actions, such as natural hazards and strong events, typically earthquakes. The preservation of architectural heritage against seismic events requires an in-depth knowledge of its dynamic properties, which can be affected also by local damages and material degradation. In this work, the experimental tests carried out on the tabernacle of the church of Santa Maria Maggiore in Spello (Italy) for the estimation of its dynamic properties are presented. The tabernacle has been built at the beginning of the 16th Century by connecting stone elements through internal iron bars, resulting in a multi-block structure with a complex dynamic behavior. An important role for the historical conservation of cultural heritage is entrusted to three-dimensional reconstruction of the built through the innovated techniques of Laser Scanner combined with UAV photogrammetry, that allowed to assess with a high degree of confidence the geometry of the built masterpiece. Ambient Vibration Tests (AVTs) were carried out using 24 accelerometric channels divided in three different setups; the procedures have highlighted the complex behavior of such systems. In order to verify any effects of non-linearity and motion in free oscillation, the tabernacle has been further instrumented through 8 displacement transducers and subjected to an increasing applied lateral force, highlighting a rocking motion due to the presence of hinges located at the base of the columns. The results, have highlighted the crucial role of diagnosis with a multidisciplinary approach in order to achieve proper decisions of interventions in the respect of the cultural heritage.