The identified pigments in Vallon roman wall painting are : egyptian blue, calcite, goethite, haematite, green earth (céladonite or glauconite) and soot or charcoal. Owing to the fire, these paintings suffered considerable damages : cracking and weakening of the plaster and of the paints and change of some colours. We observe the transition from white to grey, from yellow to red ; from red to a more or less yellowish brown or to black ; from green to grey, to red or to brown and the disappereance of the black paint. After burial in a clayey and wet soil, these paints show different types of alteration : a calcareous patina and a lot of black spots associated with different colours. These spots were found to be iron and manganese oxides, probably produced by bacterial activity. A preliminary chemical test carried out on some treated paint fragments has shown the presence of some traces of the used chemical products.
This study evaluates the adequacy of different methodologies to predict the plastic capacity and response caused by non-uniform thermal gradients through the depth of beam–columns that are loaded only axially at the centroid. Three models with different levels of complexity were used to evaluate the fire response of beam–columns under non-uniform temperature gradients: (1) code-based equations; (2) a fiber-beam element model; and (3) a shell element model that discretizes the full cross section and length and is capable of capturing local (i.e. plate) instability. The code-based equations do not predict the response satisfactorily since these equations do not properly consider temperature gradients. The fiber-beam element and shell model results correlate well to the thermal and structural response of the beam–columns tested experimentally with varying parameters. If local buckling is not expected at ambient temperature, complex shell elements are not necessary when the failure mode is fully plastic and fiber-beam elements, which are simpler and less “computationally expensive” than shells, suffice. The experiments and models also validated equations that consider thermal gradients and predict the plastic capacity and structural response of these members, which includes a moment reversal due to a shift in the section center of stiffness with increasing temperatures.