自攻螺钉增强胶合木沿胶缝横纹受压承载力试验研究

Experimental study on compressive bearing capacity of glulam strengthened by self-tapping screws along glued seam

采用自攻螺钉对胶合木梁侧进行横纹增强,并开展4组(含未增强组)胶合木梁侧横纹承压试验。结果表明,3种增强方式对胶合木梁侧的横纹承压性能均有不同程度提高,单侧通长贯入螺钉组试件最终发生了局部屈曲破坏,而其他组螺钉变形不明显;相比于未增强组试件,单侧通长贯入螺钉、双面贯入螺钉和双侧斜交螺钉组试件的横纹承压荷载分别提高了25.9%、34.5%和44.8%;单侧通长贯入螺钉组试件表现出了最高的等效横纹承压弹性模量,为333.6N/mm^(2),而其他两种增强方式的等效横纹承压弹性模量略低于未增强组试件。荷载-应变关系表明,自攻螺钉的引入能有效改善承压面下木材应变的分布。采用欧洲标准EN 408与ISO 13910标准获得的横纹承压强度较为接近,而按照《木结构试验方法标准》(GB/T 50329—2012)获得的结果偏于保守;有限元模型总体上能有效预测自攻螺钉增强后的胶合木梁侧横纹承压性能。

Self-tapping screws were used to strengthen the lateral side of the glulam beam perpendicular to grain, and lateral bearing tests on the glulam beams perpendicular to grain were carried out on four groups of glulam beams including the non-strengthened group. The results show that the three strengthening methods can improve the bearing performance of the glulam beams perpendicular to grain to different degrees. The specimens in the unilateral long-penetrating screw group eventually have local buckling failure, while the other groups have no obvious deformation. Compared to non-strengthened group, the compression loading perpendicular to grain of the strengthened groups of specimens can be improved by 25.9% for fully penetrated self-tapping screws, 34.5% for double-sides drilled self-tapping screws and 44.8% for cross-drilled self-tapping screws. The specimens with fully penetrated self-tapping screws exhibit the highest average equivalent compression modulus perpendicular to grain of 333.6 N/mm^(2). The other two strengthened groups show slight low equivalent compression modulus perpendicular to grain compared to the non-strengthened group. The load-strain relationship indicates that the use of self-tapping screws can redistribute the compression strain perpendicular to grain under the bearing area effectively. The compression intensity of pressure perpendicular to grain calculated according to European standard EN 408 is close to that obtained by ISO 13910 standard;however, the result based on the standard for test methods of timber structures(GB/T 50329—2012) is conservative. The numerical model is generally able to predict the lateral compressive behavior of the glulam beams perpendicular to grain strengthened by self-tapping screws.