Structural Analysis of Gothic Roof Trusses in View of their Conservation. Case Study of St. Paul's Cathedral, Liège (Belgium)

Abstract:

This study focuses on the structural behaviour of gothic roof structures. Starting from the case study of St. Paul’s Cathedral, Liège (Belgium), the aim of the research was to identify and understand the reasons and possible consequences of past and future structural distortions for the conservation of this historical timber roof structure.The wooden structure of St. Paul’s Cathedral is an interesting example of a 13^th and 14^th century timber-framed roof. The entire structure has mainly preserved its authentic parts even if transformations and reinforcements were made until mid-20^th century. Today, these interventions must be evaluated from a critical point of view in order to preserve the authenticity of the structure. Two interventions have been studied more particularly. Firstly, the effects of an important neo-gothic restoration made in the 19^th century and secondly, the consolidations of the frames, made after the bombings of WWII. Preliminary studies have proved that these interventions were poorly documented. As often in the past, hidden under the roofs, historic wooden structures were forgotten. However, we found some very interesting texts which have been confronted to an architectural analysis of the building and a study of the pathologies. These surveys have been used to undertake a structural analysis of the gothic roof structure in order to better understand and explain distortions and reinforcements of the frames.Due to biological deterioration, hypotheses on the resistance of wood have been implemented in the 3D models. We paid special attention to the nodes connections in order to evaluate their resistances to shear forces. Our models highlight critical areas which correspond to visible deformations and breakings produced after a bombing in 1945. The influence of the neo-gothic masonry, which encloses the wooden structure, has been also discussed. Due to a high humidity level, important structural degradations are visible on the base of the frames. Therefore, we also focused our attention on the evaluation of resistance of the principal-rafter, directly in contact with the masonry.

• Periodical: Advanced Materials Research (Volume 778)
• Pages: 895-902
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.778.895
• Online since: September 2013
• Authors: Laurent Debailleux
• Keywords: Historic Roof Structures, Mechanical Behavior, Structural Analysis

References

[1] R. Forgeur, La construction de la collégiale Saint-Paul à Liège aux temps romans et gothiques, BCRMS, XVIII, 1969, pp.3-49.

[2] P. Minke, L'architecture de la cathédrale Saint-Paul à Liège, ULg, (2007).

[3] P. Hoffsummer, Les charpentes du XIème au XIXème siècle. Typologie et evolution en France du nord et en Belgique, Eds Du Patrimoine, Paris, (2002).

DOI: 10.3406/rnord.1981.3762

[4] B. Szabo, I. Kirizsan, European historic roof structures: concepts of composition and intervention, in: Proceedings of the International Conference on Structural Analysis of Historical Constructions, SAHC 2012, Wroclaw, 105-127.

[5] D. Dirol., X. Deglise, Durabilité des bois et problèmes associés, Hermes Science Publishing, Londres, (2005).