The deformation detected in the structure of several Romanesque churches in the Vall d’Aran, built between the 12th and 13th centuries, has been caused by the poor mechanical properties of the mortar used at the time and the use of small, irregular masonry on the geometry of conical vaults. This is the main conclusion taken from the study “Grandes deformaciones en bóvedas de cañón: de formas antifuniculares a bóvedas funiculares” (‘Large deformations in barrel vaults: from anti-funicular to funicular vaults’), published in the scientific journal Revista Ingeniería de Construcción and led by the director of UIC Barcelona School of Architecture, Josep Lluis i Ginovart, lecturer Cinta Lluis-Teruel, as well as lecturers Sergio Coll-Pla and Agustí Costa-Jover from the Universitat Rovira i Virgili. 

The research was based on data collected using a terrestrial laser scanner (TLS) between 2015 and 2020. It has allowed the researchers to calibrate the deformation and displacement suffered by the churches in Santa Eularia d’Unha (12th century), Santa Maria d’Arties (12th-13th century) and Era Purificatium de Bossost (12th-13th century), in which reinforcement work had to be carried out in 1975 and 2009 due to major deformation, in some cases greater than 7%. 

In order to verify the limit state of the vaults’ equilibrium, the researchers focused on studying Santa Maria d'Arties. The results of their analysis show that, despite the deformation of the church and some of its vaults, it is still possible to draw a line of pressure in the area in which they are located, thus guaranteeing stability. “The potential for deformation in these Romanesque vaults demonstrates the importance of the rigidness of the masonry, through the way it has been cut and its size, with both mechanical and mortar filling properties. Therefore, the results of the analysis show the geometric irregularity and the enormous potential for deformation of the brickwork, although without reaching the point of collapse”, the researchers explain. 

The study also analyses the abutment measures carried out over the centuries to control these deformations, for example, by constructing large buttresses such as the one in the church of Santa Maria d'Arties, or by incorporating bell towers into the façade as counterweights, as in the case of the bell towers in Bagergue, Salardú and Vilac. “The role of the counterweight is essential to understanding the stability of these buildings, as it exerts a passive thrust that in some cases leads to the convexity of the vaults”, they point out.

“It is very difficult to find spoon-shaped vaults. Due to their major deformation, some vaults in the Vall d’Aran are arranged in the opposite way to how they should work mechanically and, in spite of this, they are still stable”, notes Josep Lluis i Ginovart.