The Simulated Timber Structure of the Volumnis’ Hypogeum in Perugia, Italy

The impressive Hypogeum of the Volumnis, prominent family from Perugia, was built in the hellenistic period (probably III - II b.C.) of the Etruscan civilization. The tomb was discovered (1840) in original conditions with incineration urnae, still preserved and now exposed in situ which allowed Scholars to propose a genealogical tree. The monument is excavated in the soft sandstone with an anthropomorphic plan, articulated in a large atrium with a final tablinum, two alae and six lateral cellae; the atrium (3,60 x 7,30 m; h. 4,40) has a two-slopes ceiling made in a way to resemble the intrados of a wooden hut roof: therefore the entire simulated carpentry – ridge beam, rafters, joists, boards etc. are carefully carved in the rock, in a true scale; the same for the alae and tablinum which have square corbelled “wooden” coverings. The arrangement is made to give to the defunted’s afterlife the same comfortable setting of the house of the living people. There are a few more examples of this kind of apparatus in Italy (e.g. some Cerveteri Tombs) and in Sardinia (Puttu Codinu and others) but none made in such a realistic way. Using 3D-Laser Scanner technology combined with industrial deviation calculation procedures required a new approach in experimentation of advanced 3D modelling with extremely large input data by developing a methodology for processing color scale images for the recognition of sensible global deformations on local elements of an ancient deteriorated structure. The analysis of deformation morphology shows surprising results: carpentry members simulate flection in stress condition of true wooden beams in similar conditions of support, span, loads. Many Scholars had studied the Monument and made careful surveys but none of them faced the problem in a comprehensive way and none noticed this realistic peculiarity; the deformations, in fact, are very slight and the traditional survey methods, even the optical ones, were not suitable to detect this kind of connotations of the pretended wooden ceiling. In order to fully document the whole monument with complete account of the features, Researchers of both the Florence and the Ferrara University decided to use the Laser Scanner methodology integrated with geological observations and survey. Detailed geometrical analysis of the scan model, for the first time, makes suspecting the presence of optical corrections in sense of enhanced perspectivity in late Etruscan funeral architecture, and allows dimension handling between repeated unaccessable points, in order to evaluate numerical series by gaussian statistical results obtaining important information about the use of ancient dimension units. The paper focuses on the simulated timber structure of which a few interpretations are proposed and discussed. The investigations and the survey lead to very interesting conclusions such as: - Reconstruction of a typical carpentry of the time - Help in the interpretation of the many but lacunose terracotta or stone models of domestic carpentries of the time - Account on the structural planning concepts and building processes of the time - Advanced 3D-modelling methodology for deviation check of ancient buildings and the possibility to extend the used appraisal methodology to similar cases.