Constrained displacement boundary condition in embedment testing of dowel‐type fasteners in LVL

Abstract

The influence of the loading orientation with respect to the grain direction of wood and the influence of the lateral dowel displacement boundary condition on the embedment behaviour of steel dowels in laminated veneer lumber (with parallel-laminated veneers) are investigated in this study. For limit states of the lateral boundary condition, the load-displacement behaviour was experimentally studied by means of full-hole embedment tests on screw-reinforced laminated veneer lumber, for two dowel diameters and up to large dowel displacements. A novel biaxial test set-up is proposed for embedment tests with constrained lateral dowel displacement boundary condition, in order to quantify laterally evoked reaction forces. Corresponding forces were found to change orientation with increasing dowel displacement and amounted to about 20% and 40% of the vertical reaction force for dowel displacements of 5 mm and twice the dowel diameter, respectively. The influence of the lateral displacement boundary condition was highlighted by comparison of the test data with a previously established data set for unconstrained embedment testing. Constrained loading showed a stiffer response and higher nominal embedment stresses, as well as a more pronounced displacement hardening, compared to unconstrained loading. KEYWORDSanisotropy, displacement boundary condition, full-hole embedment tests, reinforced laminated veneer lumber, stiffness Notation: d, dowel diameter; R a , arithmetic average of the surface roughness; ini , initial load-to-grain angle; , current load-to-grain angle; , change of loading direction; u v , vertical dowel displacement; u h , horizontal dowel displacement; u sec , secant dowel displacement; u M,v , vertical machine displacement; u M,h , horizontal machine displacement;u M,v , displacement rate;u load M,v , displacement rate at loading;u unload M,v , displacement rate at unloading; f hv , vertical embedment stress; f hh , horizontal embedment stress; f h , resultant embedment stress; F hv , vertical embedment force; F hh , horizontal embedment force; F h , resultant embedment force; F est hv , estimated quasielastic load limit; K unload elast , quasielastic unloading stiffness; K unload plast , elastoplastic unloading stiffness; K load elast , quasielastic loading stiffness; K load plast , elastoplastic loading stiffness; K reload elast , quasielastic reloading stiffness; f hv,5mm , embedment strength acc. to EN 383; f hv,2d , embedment strength at a dowel displacement of two times the dowel diameter; f hv,0.02d , embedment strength determined by 0.02d offset of the quasielastic loading stiffness; f hv,yield , embedment yield strength; f hv,EC5 , embedment strength calculated acc. to Eurocode 5, Eqs. (8.31-8.33); xx , engineering strain in grain direction; yy , engineering strain perpendicular to the grain; xy , engineering shear strain;Strain. 2017;53:e12238.wileyonlinelibrary.com/journal/str

Inclined Screw Connections With Interlayers: Beam on Foundation Non-Linear Modelling

“…where has been assumed 1.72 as found by Schweigler et al in [14,15] where a strong hardening behaviour in the direction perpendicular to the grain is observed.…”

“…The interaction between the screw and the surrounding timber along l1 is modelled through a system of discrete connectors:  A series of springs parallel to the sliding plane having elastic-perfectly plastic behaviour [14,15];  A series of springs perpendicular to the sliding plane having elastic-hardening behaviour and friction parallel to the sliding plane [14,15];  A rigid contact with damage between the common node between parallel and perpendicular springs and the node on the beam schematizing the screw (black dots in Figure 4). The series of springs parallel and perpendicular are nonlinear springs which schematize the embedment interaction in the grain direction and in the perpendicular to the grain direction.…”

Path Dependence in OSB Sheathing-to-Framing Nailed Connection Revealed by Biaxial Testing

“…Images were taken with a frequency of 0.2 Hz. The procedure for speckle pattern application and settings for the evaluation are described in Schweigler et al (2017) and Serrano and Enquist (2005), to name two examples. Basically, points on the sheathing and the wood framing were chosen and their relative change of distance in the horizontal, u x;ARAMIS , and vertical, u y;ARAMIS , directions were evaluated and compared to corresponding displacements in the actuators of the testing machine.…”