Internation Network on Timber Engineering Research 2023
One important property to be determined for cross laminated timber (CLT) is the shear stiffness at out-of-plane loading. The shear stiffness is governed by the lay-up of the CLT, and by the material stiffness of the individual layers. Typically, a shear flexible beam theory, such as Timoshenko beam theory (TBT), the so-called -method or the Shear Analogy (SA) approach, is used in evaluating test results from out-of plane loading.
In the product standard EN 16351, one approach to test for shear stiffness is to measure the local deformation (curvature) at mid-span in a 4-point bending test (which is assumed to be independent on shear deformations) and the global deformation (which includes shear deformations). By subtracting the one from the other, the shear deformations can be estimated.
This paper aims at highlighting the drawbacks of the evaluation method proposed in EN 16351 for determination of shear stiffness (rolling shear) at out-of-plane loading of CLT, by additional FE-modelling work done specifically for the current paper, provide a sound basis for decision making as regards the test standard. Furthermore, this paper explains why the basic approach of the method in EN 16351 is erroneous and how it preferably should be reformulated.