Analysis of the possible geometries of a disappeared Parthian adobe dome: from in-situ tests to finite element macro-modelling

The work studies - from a structural point of view - the possible geometries of the adobe dome covering the Round Hall building in the archaeological site of Old Nisa (Turkmenistan). Thirteen dome geometries are identified, starting from archaeological reconstructions of the disappeared dome. The dome reconstructions are subsequently modelled through nonlinear finite element analysis in order to check their static behaviour. Concrete damage plasticity model is used to describe the nonlinear behaviour of adobe masonry. To calibrate the material model, the results of an onsite experimental program characterising adobe bricks are used. The analyses show that all the 13 geometries are stable with large safety margins. The results do not allow excluding some geometries, but on the contrary, highlight that the choice of the geometry of the dome was not a critical element. This aspect supports the hypothesis that the round room was actually covered by a dome.