The aim of this study was to predict the withdrawal resistance of a screw in hybrid cross-laminated timber (CLT) composed of two types of lamina layers. A theoretical model to predict the withdrawal resistance was developed from the shear mechanism between a screw and the layers in hybrid CLT. The parameters for the developed model were the withdrawal stiffness and strength that occurs when a screw is withdrawn, and the penetration depth of a screw in layers of a wood material. The prediction model was validated with an experimental test. Screws with two different diameters and lengths (Ø6.5 × 65 mm and Ø8.0 × 100 mm) were inserted in a panel composed of solid wood and plywood layers, and the withdrawal resistances of the screws were evaluated. At least 30 specimens for each group were tested to derive the lower 5th percentile values. As a result, the developed model predictions were 86–88% of the lower 5th percentile values of hybrid CLT from the properties of the lamina layer. This shows that the withdrawal resistance of hybrid CLT can be designed from the properties of its layer.

中文翻译：

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混合交叉层压木材中螺钉的抗拔性预测

这项研究的目的是预测由两种类型的薄层组成的混合交叉层压木材（CLT）中螺钉的抗拔性。从螺杆和混合CLT中各层之间的剪切机理，建立了预测抗脱模性的理论模型。所开发模型的参数是在拔出螺钉时出现的拔出刚度和强度，以及螺钉在木质材料层中的穿透深度。通过实验测试验证了预测模型。将具有两种不同直径和长度（Ø6.5×65 mm和Ø8.0×100 mm）的螺钉插入由实木和胶合板层组成的面板中，并评估螺钉的抗拔出性。每组至少测试30个样本以得出较低的第5个百分位数。结果是，根据层层的特性，已开发的模型预测值是混合CLT的较低第5个百分位数值的86–88％。这表明可以从混合CLT的层的性能来设计其抗拉强度。