Objective  As one of the most important load-bearing components of wooden structure ancient buildings, the wall wood columns are prone to occur the defects such as cracks and decay. All kinds of defects will affect the distribution of longitudinal compressive stress of wall wood columns, leading to a reduction in its bearing capacity, which then affects its safety and directly threatens the stability of the whole building. Therefore, it is necessary to study the influence of different types of defects on the safety of wall wood columns of ancient buildings.

  Method  Firstly, in this paper, the geometric models of wall wood columns with crack, decay defects and composite defects were established, and the compression safety factor k_c of wall wood column was defined. Then, the magnitude and location of the maximum longitudinal compressive stress were simulated and analyzed using Abaqus finite element software for the crack defect model, the unilateral decay defect model, the ring decay defect model and the composite defect model, respectively. The influence of defects of different sizes on the safety of wall wood columns was investigated and verified by an example.

  Result  The unilateral decay defects and composite defects caused large deflections in the radial direction of the wall wood columns, which had a greater influence on the stability of wood columns, while wall wood columns with crack defects and ring decay defects had smaller deflections in the radial direction, longitudinal direction and tangent direction. Crack defects, unilateral decay defects, ring decay defects and composite defects had a significant influence on the maximum longitudinal compressive stress and the safety of wall wood columns. The maximum longitudinal compressive stress always occurred at the minimum effective sectional area. The longitudinal compressive stress in wall wood columns increased exponentially with the increase of defect degree and the safety factor decreased exponentially with the increase of defect degree, while the impact of composite defects on the safety of wall wood columns was greater than that of a single defect on the wall wood column safety impact. The difference in safety between semi-exposed columns and concealed columns was not much when the decay depth was same, and the safety of semi-exposed columns was much lower than that of concealed columns when the decay area was same.

  Conclusion  The crack defects and decay defects can reduce the safety of wall wood columns, and the finite element numerical simulation can calculate the maximum longitudinal compressive stress of wall wood columns, and then quantify the safety of wall wood columns, and the results can provide a basis for the repair of wall wood columns.