Mechanical properties of CLT shear connections between self-tapping screws and mortise tenons
目的正交胶合木（CLT）的出现使木结构建筑突破了以往的层高限制，但现在采用的金属连接件连接方式降低了CLT材料的使用效率，浪费了CLT材料的力学性能优势。因此，连接节点成为CLT研究的关键性问题。对榫卯连接在CLT墙体−墙体处的节点应用进行抗剪性能研究，并与自攻螺钉的连接性能相比较，以探究榫卯连接节点在CLT建筑中的应用提供科学依据。 方法分别对自攻螺钉与燕尾榫连接的两类CLT墙体节点H型试件进行单调与低周反复加载试验，得到试件在纯剪作用下的荷载−位移曲线、滞回曲线、骨架曲线等参数，并结合破坏现象比较分析了两类试件的初始刚度、最大承载力、耗能、刚度退化、强度退化等力学特性。 结果钉节点一般先于CLT材料破坏，并损坏连接处木材，而燕尾榫节点后于CLT材料发生破坏；在单调加载试验中，燕尾榫节点的延性略低于钉节点，但最大承载力、极限位移、屈服荷载、屈服位移与耗能分别高出钉节点313.50%、35.38%、370.80%、92.76%、459.64%；在低周反复加载试验中，钉节点延性较差，燕尾榫节点延性相对较好，燕尾榫正向加载的最大承载力高出钉节点455.54%，负向加载的最大承载力高出钉节点234.74%，且燕尾榫节点维持刚度和强度的能力，以及耗能能力均优于钉节点。 结论与钉节点相比，燕尾榫节点可以更大地发挥CLT材料的优点，以推动CLT建筑的工程应用。Abstract: ObjectiveThe appearance of CLT (cross-laminated timber) enables wooden buildings to break through height limitation, yet the current use of metal connectors reduces the efficiencies of CLT and wastes the mechanical capacities of CLT. Thus, the study of CLT connections becomes a vital issue. In order to provide scientific basis for the engineering application of mortise-tenon connection in CLT building, this paper makes a study of the shear performance of the mortise-tenon connection, and compares it with self-tapping screws (STS) used for wall-to-wall joints. MethodH-type CLT specimens connected with STS and mortise tenons were subjected to monotonic and cyclic loading test. Load-displacement curve, hysteretic curve and skeleton curve under pure shear loads were obtained. Mechanical properties such as initial stiffness, peak load, energy dissipation, stiffness degradation and strength degradation were investigated combining failure mode. ResultIt was shown that STS connections failed before the damage of CLT material appeared, and the damages also occurred on the wood around connections. While mortise-tenon connections failed after the damage appeared of CLT. In monotonic loading tests, mortise-tenon connections presented lower ductility than STS connections, but maximum load, ultimate displacement, yield load, yield displacement and energy dissipation were higher than STS connections by 313.50%, 35.38%, 370.80%, 92.76%, 459.64%, respectively. In cyclic loading tests, the ductility of STS connections deteriorated, but that of mortise-tenon connections became better. Meanwhile, the maximum load of pushing and pulling phase of mortise-tenon connections were respectively 455.54% and 234.74% higher than STS connections, and its ability to maintain stiffness, strength and consume energy were all better than STS connections. ConclusionCompared with the STS connections, mortise-tenon connections can allow full use of the strengths of CLT material and promote engineering application of CLT building.
表 1 钉节点、燕尾榫节点力学性能参数表
Table 1. Mechanical properties and statistics of self-tapping screw and dovetail connections
2.79 17.04 12.7 13.63 19.05 8.87 2.9 3.85 240.88 燕尾榫组
7.22 70.46 12.49 55.32 25.79 41.76 5.59 2.96 1 348.06 差值百分比
158.78 313.50 − 1.65 305.87 35.38 370.80 92.76 − 23.12 459.64 注：差值百分比为燕尾榫节点组、钉节点组力学参数的差值与钉节点组力学特征值之比。下同。Notes: the percentage of difference is equated to the ratio of the difference of the mechanical parameters of dovetail and STS to the mechanical characteristic value of STS. The same below.
表 2 钉节点、燕尾榫节点力学性能参数表
Table 2. Mechanical properties and statistics of self-tapping screw and dovetail connections
Displacement of maximum load/mm
正向 Pushing 钉节点组
16.87 4.29 13.50 7.43 燕尾榫节点
93.72 8.00 74.98 24.85 差值百分比
Percentage of difference/%
455.54 86.48 455.41 234.45 负向 Pulling 钉节点组
19.86 6.02 15.89 11.33 燕尾榫组
66.48 9.20 63.86 25.04 差值百分比
Percentage of difference/%
234.74 52.82 301.89 121.01
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