Comment on nhess-2022-93

Abstract

At the end of February 2018 the Mediterranean area of Montpellier in France was struck by a significant snowfall that turned into an intense rain event caused by an exceptional atmospheric situation. This rain-on-snow event produced pronounced damages to many buildings of different types. In this study, we report a detailed back analysis of the roof collapse of a large building, namely the Irstea Cévennes building. Attention is paid to the dynamics of the climatic event, on the one hand, and to the mechanical response of the metal roof structure to normal loading, on the other hand. The former aspect relies on multiple sources of information that provide reliable estimates of snow heights in the area before the rain came into play and substantially modified the snow quality. The latter aspect relies on detailed finite element simulations of the mechanical behaviour of the roof structure in order to assess the pressure due to snow cover loading which could theoretically lead to failure. By combining the two approaches, it is possible to reconstruct the most probable scenario for the roof collapse. As an example of building behaviour and vulnerability to an exceptional rain-on-snow event in the Mediterranean area of France, this detailed case study provides useful key points to be considered in the future for a better mitigation of such events in non-mountainous areas.