Objective Cross laminated-timber (CLT) is a new type of modern timber construction material. Dowel type connection is widely used in modern timber construction. The embedment strength is an important parameter for dowel type connection design. In order to provide a reference for the design of dowel type connections in CLT construction, the research on embedment performance of the domestic Japanese larch CLT was explored.
Method A total of 432 Japanese larch CLT specimens with half hole divided into 36 groups were subjected to the static loading. The effects of wood density, diameter and thread, glue gap and loading angle on the embedment strength of CLT were analyzed. Based on the test results, the predictability of the four methods proposed by American NDS, Canadian CSA, Kennedy, Uibel and Blaβ (U&B) were evaluated for the face side and narrow side of the Japanese larch CLT.
Result The embedment strength was positively correlated with the density of CLT, while it was negatively correlated with the dowel diameter, and it had no obvious relationship with the thread. When the dowel was driven perpendicular to the narrow side of CLT, the embedment strength under the loading angle of 0° was 3.06 times of that under the loading angle of 90°, and the embedment strength at the glue gap was the average of the two. When the dowel was driven perpendicular to the face side of CLT, the embedment strength under the loading angle of 0° was obviously greater than that under the loading angle of 90°. The calculated values were compared with the test values: (1) when the dowel was perpendicular to the narrow side of CLT, the relative errors of the CSA model were less than 8.37% under the loading angle of 0° (position A), and the relative errors of the U&B model were less than 8.56% (except for individual case) under the loading angle of 90° (position D). Both relative errors were less than 10%, which were in good agreement. (2) When the dowel was perpendicular to the face side of CLT, the relative errors of the four models were greater than 10% under the angle of 0° (position C) and 90° (position B). The relative errors of the prediction model for dowel driven perpendicular to the face side of CLT established in this paper were less than 5.31% and 6.04%, respectively, both less than 10%, which were in good agreement.
Conclusion Density, dowel diameter and loading angle are important factors influencing the embedment strength of CLT. The calculation methods of embedment strength for domestic Japanese larch CLT are as follows: when the dowel driven perpendicular to the narrow side of CLT, the CSA model can be used under the loading angle of 0° and the U&B model can be used under the loading angle of 90°. When the dowel driven perpendicular to the face side of CLT, the prediction model established in this study can be used under the loading angle of 0° and 90°.
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