A Model for the Analysis of Sun Radiation Structures Exposed to Open Air: Consideration on its validity and usefulness based on its experimentation in situ

摘要

The definition of the thermal dynamics of a structure-work of cultural interest is important both from the microclimatic point of view and from the structural one. Elastic and plastic deformations, due to phenomena of heat exchange, influence, in a significant way, the mechanical behaviour of the structure. Dealing with objects exposed to open air, one of the main sources of heat radiation is, obviously, the sun. Consequently, it is significant to evaluate the importance that solar radiation has in the global heating dynamics of the structure. Therefore, while studying the system Marcus Aurelius-Capitolium square, it was decided to support the investigations in situ (carried out by using thermovision and thermocouples) with the realization, on computer, of a system that could define the theoretical relationship existing between solar dynamics and the bronze monument. Correlation between information deduced from such a model and data obtained in situ, gave useful results and constituted a significant instrument for the analysis of the concrete thermal model of the investigated structure. The opportunity to deepen and improve such an experience arose when the Soprintendenza per i Beni Architettonici ed Ambientali di Firenze e Pistoia asked for a contribution to the studies and investigations aimed to define the thermal model of the Dome of Santa Maria del Fiore. The remarkable differences between the two structures (and situations) required significant modifications, not only to the system developed on computer (and to the relating mathematical model), but also (and mostly) to the contents of its informative structure and to the procedures by which such information was given to the user to support their analysis. A comparative analysis, based on the examination of the analogies and divergences of the two experiences is very significant. It brings us to develop observations and considerations on the validity and utility (and thus "economicity") of the proposed model. In fact, it enables us to evaluate figures such as its applicability in different situations, the significance of the information that it gives to the user, its efficacy as a support for the definition of the thermal dynamics of a structure exposed to open air.