Brittle Failures in Timber Beams Loaded Perpendicular to Grain by Connections

A state-of-the-art review of simple analytical fracture mechanics models for calculation of the splitting capacity of timber beams loaded perpendicular to the grain direction by connections is presented. It is shown that most of the already available models are closely related and appear naturally as special cases of the most general model available. A new model, which is a semiempirical extension of an existing model based on a beam-on-elastic-foundation theory, is proposed. The so-called van der Put model, which forms the theoretical basis for the splitting equations used in the European and Canadian timber design codes, appears as a special case of the proposed model. The treatment of the splitting problem in some major timber design codes is reviewed and discussed based on the theoretical models and new test results. The approach used in the European timber design code where the maximum shear force on either side of a connection is considered rather than the total load applied on a connection is not in agreement with the test results presented. While the European and Canadian timber design codes apply a constant value for a material property related to the splitting performance irrespective of the material considered, the presented experimental results indicate that the material property for Radiata pine laminated veneer lumber can be close to twice the value for Douglas fir glulam. The presented test results also show that despite the fact that Douglas fir glulam has a significantly higher mean perpendicular-to-grain tensile strength than Radiata pine laminated veneer lumber, the splitting failure load of Radiata pine laminated veneer lumber is nevertheless significantly higher than that of Douglas fir glulam. The latter finding seems to be in disagreement with the German timber design code, according to which the splitting strength is proportional to the perpendicular-to-grain tensile strength.