云杉胶合木钢板斜螺钉连接的剪切性能研究

Study on shear property of spruce glulam and steel plate connected with inclined screw

为准确评价斜螺钉连接钢 木节点的剪切性能,探明其受力机理,以云杉胶合木、钢板和自攻螺钉作为研究材料,测试不同荷载方向与受力情况下斜螺钉连接节点的承载性能,将试验数据与国外规范中的计算模型进行对比,提高了侧边钢板 胶合木(钢 木)斜螺钉连接节点承载性能的预测能力。结果表明:自攻螺钉与剪切面之间的角度变化对其在钢 木节点承受剪 压复合应力的承载力影响不明显,当偏转为剪 拉复合应力时,节点承载力明显增大,并在30°~45°获得最大值;剪 压复合应力时,现行EC5公式计算剪 压节点的极限承载力非常不安全;EC5的刚度预测结果在剪 压复合应力区和垂直剪切面钉入时,与试验值吻合度很高,但对剪 拉区节点的滑移模量没有预测性;将Tomasi模型应用于斜螺钉连接钢 木节点滑移模量理论计算时,在45°~90°时与试验值吻合度极高。单颗自攻螺钉的抗拔刚度计算节点滑移模量的方法极为有效,具有较高的借鉴意义。

In modern timber structure,self-tapping screw has been widely used.The self-tapping screws in the inclined screw connection joint bear both axial and lateral loads.At present,there are many specifications concerning the design and calculation formula of inclined screw connection.The existing specifications are the secondary combination formula of the lateral shear strength and axial strength of the screw to calculate the bearing capacity of the screw connection under the load state of shear stress and axial stress at the same time.This calculation method underestimates the strength of inclined screw connection,and the theoretical value of the calculation model is too conservative.With the continuous development of self-tapping screws in new structures,the self-tapping screws with strong stiffness and axial load-bearing performance usually connect the wood-wood member and steel-wood member with an inclined angle to obtain the connection joints with better load-bearing performance compared with the traditional connection forms.To evaluate the shear properties of steel-wood joints with inclined screw connections more accurately,and to prove the mechanism of its forces,the spruce glulam,steel plate and self-tapping screw were taken as the research materials,the bearing capacity of inclined screw joints under different loading directions and different loading conditions was examined.The experimental data were compared with that obtained from the calculation model in foreign codes,and the predictive capacity of the bearing capacity of side steel plate-glulam inclined screw joints was revised.The results showed that the change of angle between self-tapping screw and shear plane had no obvious effect on the bearing capacity of steel-wood joint under shear-compression composite stress.When the self-tapping screw deflected to shear-tension composite stress,the bearing capacity of joints increased significantly,and the maximum value was obtained between 30°and 45°.When the shear-compression stress was applied,it was very unsafe to calculate the ultimate bearing capacity of the shear-compression joint by the current EC5 formula.The stiffness prediction results of EC5 coincided with the experimental values showed very well in the shear-compressive stress zone and the nailing of the vertical shear plane,but had no prediction for the slip modulus of the shear-tension zone joints.When Tomasi model was applied to the theoretical calculation of slip modulus of steel-wood joints with inclined screw connections,the agreement between 45°to 90°and experimental values was very good.The method of calculating the slip modulus of joints by the pull-out stiffness of a single self-tapping screw was very effective and had a high reference value for the industrial applications.