Embedment tests perpendicular to the grain – optical measurements of deformation fields

This paper reveals additional knowledge on the bearing behaviour of single fastener connections. By means of non-contact full-field deformation measurements the deformation fields were recorded for different test configurations. It is shown that embedment is a very local phenomenon causing large stress concentrations and gradients in the dowel vicinity. However, timber as being considered a highly orthotropic material loaded in the weak planes appears to be able to redistribute stresses and to activate material outside the dowel vicinity. This causes the ultimate strength to be governed by the deformation ability underneath the dowel. This effect is not detectable in case of rather small specimen geometries, however, it becomes evident in case of specimens of structural sizes. Finite element simulations show localization effects to be much more evident in case of isotropic materials like steel, what verifies an apparent load-sharing effect for timber perpendicular-to-grain.