In traditional timber structures, the columns and beams are typically connected using mortise–tenon joints consequently, interior notches are required on the columns.
Although the flexural strength under 3P bending is higher than that of 4P bending based on many experimental results, the difference in the rates of increase between 3 and 4P load configurations varies, depending on the material. According to the evaluation of the load configuration effect based on the Weibull theory, the load-bearing capacity of a beam subjected to midspan 3P bending is approximately 1.21 that of 4P bending, and influenced by the stressed volume difference. In terms of traditional timber columns, the concentrated force is transferred from the beam end to the column and subjected to three-point (3P) bending. The characteristic strength is normally determined through four-point (4P) bending tests considering the scale factor. The load-bearing capacity of a bending member is generally estimated as the product of the effective section modulus and the characteristic bending strength. In this study, the bending performance of columns in a traditional timber frame was investigated.
Considering that the forces generated on the joints, beams, and hanging walls are transmitted to the columns, the damage limit of the columns directly affects the load-bearing capacity of the entire structure. Based on quasi-static tests on a frame with deep beams and hanging mud walls, it was observed that the bending behavior of columns, moment resistance of the tenon–mortise joints and shear resistance of the hanging walls contributed to the lateral resistance of the entire frame. In evaluating the lateral resistance of traditional Japanese timber structures consisting of large dimensional beams, columns, and hanging walls, the performance of the main structural elements should be assessed in addition to the evaluation of shear walls. The fracture position and the standard deviation of the bending strength were affected not only by the notch depth, but also by the notch width on the tensile side of the column. The results indicated that the mean bending strength of columns with three different notch types was consistent with those without notches, the continuous timber on both sides of the notch had a beneficial effect on maintaining a higher strength and reducing the stress intensity around the notch. The reduction in the load-bearing capacity of columns with different types of interior notches in traditional Japanese timber structures was determined through experimental tests and statistical analysis.
First, the bending behaviors of columns under three-point and four-point load configurations were compared to obtain a suitable referenced strength of a column without notches. In this study, the columns with interior notches in traditional Japanese timber frames were selected as the research object, and static bending tests were performed to investigate the effect of interior notches on the flexural properties of columns.
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