Numerical simulation of the safety influence of defects on Qijia-beams of ancient timber building

ObjectiveThe Qijia-beams are used as the main load-bearing members for Chinese ancient timber building. The safety performance of whole wood structure is directly affected by the bearing capacity safety of Qijia-beam. Factors, such as surrounding environment and load for a long period, lead to different degrees of the defects in the wooden beam. These defects will affect the tensile stress and shear stress distribution, as well as the bearing capacity safety of the wooden beam. Therefore, it is necessary to study the influence of different defect types, sizes and locations on the safety of bearing capacity of the Qijia-beam.

MethodAbaqus finite element software was used to simulate the stress state of the beam with different defects such as crack, decay and hole. By quantifying the size and location of the defects, the single parameter numerical simulation analysis of different damage factors was carried out to determine the maximum working stress location of the wood beam with defects, analyze the sensitive location of the damage of the wood beam, and investigate the variation patterns of the bearing capacity of wood beams.

ResultThe results showed that the types of different defects had different influence on the safety of the Qijia-beam. External decay had the greatest influence on the bearing capacity of the Qijia-beam, followed by hole defect, and the impact of crack defect was relatively minimal. For the bending beams in the elastic stage, the defects had the greatest influence on the bearing capacity safety of the Qijia-beam when it was located in the tension zone between two under Jiagua-columns. The influence of different defect sizes on the bearing capacity of the Qijia-beam was different. With the increase of the crack depth, the decay depth, and the hole size, the safety of the wooden beam was gradually reduced.

ConclusionDue to the existence of local defects, the bearing capacity of the Qijia-beams would be decreased. The research of this paper provides numerical simulation, which could accurately determine the maximum tensile stress of the wooden beam. It is a good method to quantitatively study the influence of defect on the safety of Qijia-beam and to determine the location of Qijia-beam safety monitoring.