Structural analysis and damage assessment of a fortified church – A case study: The Evangelical Church of Apos, Sibiu County

Abstract

Globally, there is a wide range of monuments that require conservation and restoration work in order to maintain their values as a whole, both from the aesthetic and historical perspective and to ensure their preservation for future generations. The aim of this paper is to showcase the historical development of the fortified church structure in Apoș, in addition to examining the reasons for its structural damage and exploring possible ways to strengthen the entire church – tower complex. The Evangelical Church is located in the village of Apoș, in the central region of Transylvania, along the Hârtibaciu Valley. This region is of national importance, being part of the Hârtibaciu Plateau and also within the Natura 2000 sites. The church complex consists of the church itself, which is also listed in the Historical Monuments List with the code SB-II-a-B-12313, the bell tower and the clergy house. However, this paper concerns only the church and the tower. The evolution of the church spans over several centuries, during which its structure underwent reconfigurations, consolidation works, but also invasive interventions with incompatible materials that further altered the entire structure and its behaviour. Thus, from the point of view of interventions, they were carried out progressively, the most extensive works being the replacement of the nave ceiling with cylindrical vaults and the replacement of the choir ceiling with a semispherical vault, as well as the consolidation works of the building in the 20th century. The investigation of the Evangelical Church was carried out, first of all, by conducting an on-site investigation, followed by using traditional survey methods in order to identify the structure failures. Additionally, contemporary visualization methods, such as three-dimensional laser scanning, were utilized to gather information on dimensions, heights and ornament details. Through these steps, a survey was obtained that includes accurate data on the church complex. Following these stages, the main degradations identified were a series of cracks caused by differential settlements and the lack of cooperation between structural elements, mechanical damage caused by the detachment of the buttresses from the walls and due to the sliding of the land towards the south, after the demolition of the fortifications. Additionally, two types of brickwork damage were identified: pronounced crack indicating its displacement, contributed by seismic activity and smaller but numerous cracks indicating the disintegration of the brickwork caused by differential settlements combined with prolonged moisture. Besides these, human factors and execution defects were identified, as well as physicochemical degradations with internal causes, such as composition defects or crystal cohesion defects. The repair and consolidation works, including seismic safety measures, have proposed technologies based on the principles of reversibility and preservation of the church’s authenticity. Thus, the main interventions aim to strengthen the structural walls, arches and vaults, eliminate the source of humidity causing the erosion of the masonry through capillary water infiltration, strengthen the floors, roof structure and openings, as well as the interior elements, such as balconies and stairs.