The numerical assessment of a full-scale historical truss structure reconstructed with use of traditional all-wooden joints

This paper focuses on description of the mechanical behavior of the historical gothic truss of St. James's Church in Brno. The numerical approach using finite element analysis (FEA) provided virtual assessment of the truss with a prediction of its behavior after simulated restoration using joints at locations of possible failure. The historical truss was subsequently analyzed by both beam truss structure and detailed 3D solid lap scarf joint modeled by reduction technique using substructuring. Static analyses were carried out using the finite element method (FEM) in order to establish a reliable numerical model and assess the static risks. The finite element models in ANSYS software assume fully orthotropic material properties of wood (Norway spruce and European beech) with elastic behavior. Results portrayed very good design of the assessed truss in the global mechanical behavior despite the rigidity of joints varied in longitudinal and transverse directions of the frames. Changes in global truss behavior were observed, but the changes in objective vertical displacement were not high. The differences based on rigidity level were not more than 7% of maximum vertical displacement of beams. The minor differences were recognized in the global truss behavior owing to new positions of implemented joints in the truss. Analyses showed each member in the truss contributes to global truss rigidity and stability to different degree. Further, analyses showed areas in the truss where it was necessary to correct joints orientation.