CLT楼板半层搭接节点的面外弯曲性能试验研究

Experimental Study on Out-of-plane Bending Performance of CLT Floors with Half-Lapped Joints

为研究半层搭接节点对正交胶合木(CLT)楼板双向抗弯承载力的影响,分别对CLT楼板半层搭接节点试件沿强轴和弱轴方向进行面外加载弯曲试验.归纳了强轴和弱轴方向受弯的试验现象和极限状态的破坏模式,考察了螺钉直径、螺钉间距、搭接长度对抗弯极限荷载、跨中截面应变的影响.结合试验现象,总结了弱轴方向受弯极限状态时自攻螺钉的变形特征.提出了半层搭接节点弱轴方向抗弯承载力的计算方法,将其计算结果与抗弯极限荷载试验值作对比.研究结果表明:强轴方向受弯试件的破坏模式是混合模式(销槽承压破坏,以及木层板的受拉破坏或滚剪破坏);弱轴方向受弯试件的搭接上部有两种破坏模式,包括模式Ⅰ(销槽承压破坏和钉帽拉穿破坏)、模式Ⅱ(搭接上部半层层板顺纹劈裂和钉帽拉穿破坏).增大螺钉直径、减小螺钉间距对强轴方向抗弯承载力无显著影响,增加搭接长度、减小螺钉间距能够显著提高弱轴方向抗弯承载力.提出的计算方法能够合理地预测半层搭接节点弱轴方向抗弯极限荷载,可为推广CLT双向楼板的应用提供理论研究基础和结构设计参考.

To investigate the influence of the half-lapped joints on the bending moment capacity in the two-way directions of Cross-Laminated Timber(CLT)floors,out-of-plane bending tests in the major and the minor strength directions were performed,respectively. The test phenomena and failure modes at ultimate state in both loading directions were discussed,and the effects of the screw diameter,the screw spacing,and the lap length on the bending moment capacities and the strains in the mid-span cross-sections were investigated. Combined with the test phenomena,the deformation characteristics of the self-tapping screws in the minor direction at ultimate state were summarized. A calculation method for determining the bending moment capacity in the minor direction was developed,and the calculation results were compared with the test values. The results showed that the failure mode of the specimens in the major direction was the mix mode(the embedment failure,and the tensile fracture or the rolling shear of the layer),and those of the specimens in the upper lap in the minor direction were characterized by two failure modes,including the mode Ⅰ(the embedment failure and the pull-through failure),and the mode Ⅱ(the splits along grain in the upper lap and the pull-through failure). The increase of the screw diameter and the decrease of the screw spacing had no significant influence on the bending moment capacity in the major direction. The increase of the lap length and the decrease of the screw spacing significantly improved the bending moment capacity in the minor direction.The calculation method proposed in this paper predicted the ultimate bending resisting load in the minor strength direction reasonably,which laid the theoretical foundation and provided the structural design reference for the promotion of CLT two-way slabs in the engineering application.