Various design codes and design proposals have been proposed for glued laminated timber beams with round holes, assuming that the entire beam is composed of homogeneous-grade timber. However, in Japan, glued laminated timber composed of homogeneous-grade timber is rarely used for beams. In this study, the difference in the load-bearing capacity of glued laminated beams composed of homogeneous-grade timber and heterogeneous-grade timber with round holes when fractured by cracking was investigated experimentally and analytically. The materials used in the tests were glued laminated beams composed of homogeneous-grade Scots pine timber with a strength grade of E105-F345 and heterogeneous-grade Scots pine timber with a strength grade of E105-F300. Experiments confirmed that although the glued laminated beams composed of heterogeneous-grade timber have a lower material strength in the lamina with holes, its resistance to fracturing due to cracks associated with the holes is almost the same as that of the glued laminated beams composed of homogeneous-grade timber. The stresses acting on the holes in the laminated timber with holes of less than half the beam height were lower in the glued laminated beams composed of heterogeneous-grade timber than in the glued laminated beams composed of homogeneous-grade timber. The ratio of the stresses was found to be approximately equal to the ratio of the maximum bending stress or the maximum shear stress acting on the inner layer lamina, as determined by Bernoulli–Euler theory.

中文翻译：

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圆孔胶合层压木梁强度研究：同等级和非同等级木材的结构性能差异

假设整个横梁是由同等级的木材组成的，则针对带有圆孔的胶合层压木梁提出了各种设计规范和设计建议。然而，在日本，由均等级木材组成的胶合层压木材很少用于横梁。本研究通过实验和分析方法研究了均质木材和异质木材带圆孔的胶合层压梁在开裂时的承载能力差异。试验中使用的材料是由强度等级为E105-F345的均质等级的苏格兰松木和强度等级为E105-F300的异质等级的苏格兰松木组成的胶合层压梁。实验证实，尽管由异质木材构成的胶合层压板在带孔的层板中具有较低的材料强度，但其与孔相关的裂纹导致的抗破裂性几乎与由均质胶合板构成的胶合层压板相同。高档木材。异物级木材构成的胶合层压梁中，孔小于梁高一半的层压木材中的孔所受的应力低于均质级木材的胶合层压梁。发现应力的比率大约等于作用在内层薄板上的最大弯曲应力或最大剪切应力的比率，这由Bernoulli-Euler理论确定。由于与孔相关的裂纹，它的抗破裂性几乎与由均等级木材组成的胶合层压梁相同。异物级木材构成的胶合层压梁中，孔小于梁高一半的层压木材中的孔所受的应力低于均质级木材的胶合层压梁。发现应力的比率大约等于作用在内层薄板上的最大弯曲应力或最大剪切应力的比率，这由Bernoulli-Euler理论确定。由于与孔相关的裂纹，它的抗破裂性几乎与由均等级木材组成的胶合层压梁相同。异物级木材构成的胶合层压梁中，孔小于梁高一半的层压木材中的孔所受的应力低于均质级木材的胶合层压梁。发现应力的比率大约等于作用在内层薄板上的最大弯曲应力或最大剪切应力的比率，这由Bernoulli-Euler理论确定。异物级木材构成的胶合层压梁中，孔小于梁高一半的层压木材中的孔所受的应力低于均质级木材的胶合层压梁。发现应力的比率大约等于作用在内层薄板上的最大弯曲应力或最大剪切应力的比率，这由Bernoulli-Euler理论确定。异物级木材构成的胶合层压梁中，孔小于梁高一半的层压木材中的孔所受的应力低于均质级木材的胶合层压梁。发现应力的比率大约等于作用在内层薄板上的最大弯曲应力或最大剪切应力的比率，这由Bernoulli-Euler理论确定。