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Qiu L.P.,Harbin Institute of Technology | Zhu E.C.,Harbin Institute of Technology | Van De Kuilen J.W.G.,Holzforschung Munich
European Journal of Wood and Wood Products | Year: 2014

The main objective of this paper is to develop extended finite element method (XFEM) based models to simulate the crack propagation behavior of wood. Fracture toughness of Mode I and II and elastic properties of Northeast China larch were determined by experiments. Tests on three full-size curved Glulam beams subjected to four-point bending were conducted. XFEM based models incorporating ABAQUS were developed to simulate the experiments and investigate cracking of wood numerically. The numerical results correlate with experiments in terms of crack propagation direction and the applied forces for crack growth. © 2013 Springer-Verlag Berlin Heidelberg.

van de Kuilen J.-W.,Holzforschung Munich | van de Kuilen J.-W.,Technical University of Delft | Sandhaas C.,Technical University of Delft | Sandhaas C.,Karlsruhe Institute of Technology | Blass H.J.,Karlsruhe Institute of Technology
RILEM Bookseries | Year: 2014

Present-day very high strength steel (vhss) grades show high plastic deformation capacity whilst reaching tension strengths of up to 1400 MPa. These properties open new application fields in timber engineering. Replacing mild steel dowels in timber joints with vhss dowels should lead to higher load carrying capacities or to leaner joints (thinner dowels and smaller cross sections) without losing the desired joint failure mode with one or two plastic hinges per shear plane. Extensive test series on double-shear timber joints with slotted-in steel plates have been carried out using 12 mm and 24 mm dowels. The chosen timber species were spruce, beech and azobé. One, three and five dowels in a row were tested and the used dowel steel grades were high strength steel (hss) with a mean tension strength of 590 MPa and vhss with a mean tension strength of 1390 MPa. The test outcomes have shown that joints with vhss dowels reach a higher load carrying capacity than the same joints using hss dowels, but are still able to develop plastic hinges. No correlation between density, load carrying capacity and stiffness within one wood species could be found. The effective number of fasteners showed a trend to be lower for the joints with vhss dowels and at the same time, is dependent on the used wood species as generally, ductile species such as beech show large deformations and subsequently high load carrying capacities if one dowel is used. © RILEM 2014.

Sandhaas C.,Karlsruhe Institute of Technology | Ravenshorst G.J.P.,Technical University of Delft | Blass H.J.,Karlsruhe Institute of Technology | Van De Kuilen J.W.G.,Holzforschung Munich
European Journal of Wood and Wood Products | Year: 2013

Embedment tests parallel-to-grain using dowels with different steel grades and five wood species were carried out. The specimen sampling with regard to density was random and the specimens were tested at different moisture contents. Furthermore, own tests were extended by results from literature. Observed ductility aspects using different wood species are discussed. Comparisons with the existing design equation in Eurocode 5 were made. It was found that the equation penalises species with higher densities. An adjustment of density and embedment strength to 12 % moisture content reduced the scatter considerably. Moreover, based on the test results, the sophisticated distinction of softwood in many strength classes based on minor differences in density is considered to be overly precise as far as embedment strength is concerned. An influence of the dowel steel grade was measured although the dowels remained elastic as required by standard embedment test protocols. © 2013 Springer-Verlag Berlin Heidelberg.

Treml S.,Holzforschung Munich | Engelhardt M.,Holzforschung Munich
Wood Science and Technology | Year: 2013

In the present paper, preliminary tests on the relaxation behaviour of loose-fill cellulose insulation of varying quality are discussed in order to reveal the dependence of the permanent residual stiffness on the settlement behaviour of the material. The objective is to evaluate the potential of relaxation tests to understand the impact of the material structure on the settlement behaviour. © 2013 Springer-Verlag Berlin Heidelberg.

Treml S.,Holzforschung Munich | Jeske H.,Holzforschung Munich
European Journal of Wood and Wood Products | Year: 2012

Cutting of ring porous hardwoods into high quality OSB strands is quite problematic due to the anatomical structure of the wood. Square scantlings with defined annual ring orientation were cut with a flat disc chipper to illustrate the effect of annual ring orientation of selected ring porous hardwoods on the quality of OSB strands during cutting. It was shown that depending on the annual ring orientation splinter formation already occurs at the cutting edge. © Springer-Verlag 2011.

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