Load-to-grain angle dependence of the embedment behavior of dowel-type fasteners in laminated veneer lumber

• Published in: Construction & building materials Vol. 126; pp. 1020 - 1033
• Main Authors: Schweigler, Michael, Bader, Thomas K., Hochreiner, Georg, Unger, Gerhard, Eberhardsteiner, Josef
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.11.2016; Elsevier B.V
• Subjects: Analysis; Anisotropy; Byggteknik; Civil engineering; Digital image correlation; Displacement boundary conditions; Ductility; Fasteners; Forestry and Wood Technology; Full-hole embedment tests; Laminated veneer lumber; Lumber; Mechanical properties; Skog och träteknik; Austria; Sweden; Laminated veneer lumber; Displacement boundary conditions; Anisotropy; Ductility; Full-hole embedment tests; Digital image correlation
• ISSN: 0950-0618; 1879-0526; 1879-0526
• DOI: 10.1016/j.conbuildmat.2016.09.051

•Embedment tests from parallel to perpendicular to the grain with 15° step size.•Experiments on reinforced LVL with high ductility up to large dowel displacements.•Analysis of the nonlinear dowel displacement path caused by unconstrained loading.•Comparison of test data with Eurocode5 design equations. Load-to-grain angle dependence of the embedment behavior of steel dowels in laminated veneer lumber, as a consequence of the anisotropic material behavior of wood, is experimentally investigated in this study. As a novel issue, in addition to the stress dependence, the displacement path of the dowel depending on the load-to-grain angle, is discussed. Full-hole embedment tests of screw-reinforced LVL specimens up to dowel displacements of two times the dowel diameter and thus, representative for highly ductile dowel connections were conducted. Tests were performed with unconstrained lateral displacement boundary conditions of steel dowels with a diameter of 12mm and 16mm. Surface deformations were monitored with a full-field deformation measurement system. Increasing the load-to-grain angle caused reduced quasi-elastic limits and loading stiffness. However, for load-to-grain angles of 60° and higher, a pronounced displacement-hardening effect, leading to high embedment stresses at large dowel displacements, was observed. For the investigated dowel diameters, surface strains and plastic deformations around the dowel indicate an almost dowel diameter independent load bearing area, which might explain higher nominal embedment stresses and consequently a more pronounced hardening effect of the smaller dowel diameter. Dowel displacements perpendicular to the initial loading direction, i.e., nonlinear displacement paths of the dowel, were related to the anisotropic stiffness of wood and densification effects close to the dowel. The established experimental dataset was compared to current European timber engineering design equations and could serve as input to analytical and numerical models of dowel connections.