Structural performance of CLT shear connections with castellations and angle brackets

The advent of digital fabrication technologies and mass timber products such as cross-laminated timber (CLT) have facilitated the use of traditional carpentry joints in modern mass timber construction. Through contact bearing, mortise and tenon castellated joints can also provide high shear strength and stiffness between timber members when compared to connections using mechanical connectors/fasteners. In this study, a total of 29 connection specimens using carpentry castellations and six connection specimens using commercial angle brackets were tested under monotonic loading to evaluate their structural performance. These specimens used five-ply (175 mm thick) and seven-ply (275 mm thick) CLT panels. It was found that the shear strength and stiffness of the castellated joints were 2.5 and 7 times greater than the specimens using the commercial angle brackets. A simplified component-based analytical model was also developed to predict the strength of the castellated joints loaded parallel and perpendicular to grain of the CLT outer layers. The simplified model was found to be adequate in estimating strength given the model limitations. Overall, the study showed that these castellated CLT joints can provide one effective connection type with high shear strength and stiffness for CLT structures.

Automated summary

The study found that traditional carpentry joints such as mortise and tenon castellated joints can provide higher shear strength and stiffness compared to connections using mechanical connectors/fasteners, especially in modern mass timber construction. A simplified component-based analytical model was developed to predict the strength of the castellated joints loaded parallel and perpendicular to grain, showing that these joints can offer an effective connection type with high shear strength and stiffness for CLT structures.