Finite element simulation study on the degradation of load-bearing performance of longitudinal crack damaged wooden beams

To evaluate the impact of cracks on the load-bearing capacity of wooden beams in buildings, this study established an anisotropic linear elastic finite element (FE) model using rectangular-section beams of Pinus sylvestris var. mongolica Litv. The model simulated three-point bending under minor deformation conditions, systematically analyzing the effects of span-height ratio, longitudinal crack depth, and crack location on beam load-bearing capacity. Digital Image Correlation (DIC)experimental verification was conducted using two groups of physical beams: one without cracks and another with longitudinal cracks. Simulation results indicate that crack depth and span-height ratio are the primary factors determining load-bearing capacity degradation, while crack position only causes an additional 1-2% increase in degradation rate when near the loading point. The load-bearing capacity decreases most rapidly in beams with small span-height ratios as cracks deepen. Through polynomial regression, a load-bearing capacity degradation rate estimation formula with R²=0.99 was developed, which enabling quantitative prediction of remaining load-bearing capacity under engineering deflection limits (L/250). The DIC full-field displacement-strain cloud diagram showed excellent agreement with FE results, validating the model's reliability. This research provides a rapid, non-destructive, and high-precision theoretical tool for daily inspection, remaining life assessment, and reinforcement decisions in timber structures.