Modelling a double-shell dome interconnected with a wooden structure: San Gennaro Chapel in Naples

Abstract

The remarkable antique wooden umbrella structure embedded within the double dome of the Cathedral of Naples astonishes with its complexity and grandeur. Over the past decade, eminent scholars have investigated this structure; however, the authors believe that it warrants an additional perspective – an interdisciplinary approach that integrates the complexity of graphic representation with structural assessment – to understand better the purpose behind the construction of such an extraordinary and uncommon element within Neapolitan Baroque masonry domes. This study aims to analyse the dome as a unified system by employing a combination of methodologies, including limit analysis and the study of reticular wooden structures. The theoretical framework considers the principles governing masonry structures (modelled as no-tension materials) and timbre elements analysed through elastic theory. The focus is on defining the interaction between these two structural systems, building upon Heyman’s theories on curved masonry structures. The combination of these distinct materials results in a structurally complex and inhomogeneous system, revealing the rationale behind creating a ‘forest’ of solid chestnut wood. To fully comprehend the function of the entire structure, it is crucial to recognise that the timbre framework supports the upper dome without imposing additional loads on the lower one. This design was conceived to ensure the stability of the elliptical upper dome. The research investigates the structural and functional imperatives that led engineers to device such a sophisticated system in a highly challenging environment. Furthermore, it examines the changes in the structural behaviour of the current system compared to the original design, which did not account for the presence of the wooden structure.