Assessment and Structural Analysis of Historic Timber Structures of the Trøndelag Family of Churches

Abstract

In Norway, an important group of wooden medieval structures are the surviving timber roofs of stone churches. These structures demonstrate the great craftsmanship of medieval carpenters. They have remarkable cultural and technical value, but detailed investigations and assessments of the structures have not yet been carried out.

The work focuses on a specific family of stone churches with wooden roofs, namely the main five Trøndelag churches. The Trøndelag family of churches were built between 1100 and 1350AD and it has an inestimable heritage value. The main structure of the churches is comprised of wooden trusses connected by collaborating wooden planks, all supported by stone walls.

The work begins by assessing the geometry of the churches’ structures, material, and deformations with a chosen assessment scheme in order to provide an argumentative background, information and data for calculations. The thesis focuses primarily on the structural analysis of the roof system with particular care to express a correct representation of the mechanical properties of the joints and the interactions between the main trusses’ structure and the wooden planks, often otherwise disregarded. The evaluation phase consists of an in-situ assessment and an experimental campaign on wooden dowel connections. The data collected in this phase are used to define the behaviour of the wooden connections first, and then to study the global structure.

The work describes the behaviour of the wooden connections and their failure modes. It defines a new formula for failure mode of wooden dowel connections. It finally shows that the influence of the collaborating plank is clear, and it affect the in-plane structural behaviour of the Trøndelag family of churches structures.