Experimental and Theoretical Study on the Flexural Mechanism of Spliced Timber Columns Under Four-Point Bending Loading

To study the effects of different spliced forms and spliced lengths on the flexural performance of traditional spliced timber columns, four-point bending tests were conducted. A total of 14 specimens were designed across three groups, including one group of solid timber columns and two groups of spliced timber columns featuring the half-lap joint and cross-lap joint forms, all with a combined length of 2000 mm. Test results indicate that the half-lap joints exhibited discrete surface strain and stress concentration due to the discontinuity of the joint structure. Their flexural load-bearing capacities ranged from 6.6% to 11.6% of the solid timber columns. In contrast, the cross-lap joints achieved continuous strain distribution by virtue of the spliced head’s self-locking effect, demonstrating superior overall deformation coordination. Their flexural load-bearing capacities ranged from 8.4% to 11.1% of the solid timber columns. A noticeable reduction in initial stiffness was observed for the spliced columns. The solid timber columns and half-lap joints primarily exhibited brittle failure, while the cross-lap joints displayed plastic failure. Furthermore, a flexural load-bearing capacity model was developed for the spliced timber columns. By comprehensively considering the material strength reduction and the geometric parameters of the joint, the model was validated through experiments, demonstrating high reliability. The mean ratio of test-to-theoretical values was 1.0005, with a mean absolute percentage error of 3.2%; the coefficient of determination was 0.998 for the half-lap joints and 0.986 for the cross-lap joints. This model provides an accurate theoretical assessment tool for the repair projects of traditional timber structures.