Capacity prediction of welded timber joints

Abstract

Linear vibration welding of timber structural elements provides new opportunities to potentially achieve structural joints. This paper investigates to which extent welded joints can be considered for load-bearing structural joints. On the basis of a series of experimental and numerical investigations on a series of welded single-lap joints, failure modes were identified, and the associated failure criterion was quantified. A probabilistic method subsequently allowed accurately predicting the capacity of the tested wood welded joints exclusively based on objective input data, including an estimate of the scattering due to the material's inherent variability.

Moment resisting connections composed of friction-welded spruce boards: experimental investigations and numerical strength prediction

“…This makes the contribution of ''lessstressed'' elements almost negligible. As a result, suppressing the positive influence of compressive stresses is unlikely to flaw the overall result significantly, which has been proven in previous studies (Keller and Vallée 2006;Tannert et al 2012;Vallée et al 2011;Hahn et al 2012). As shown in the figures, stresses concentrate towards the edges, indicating that load transfer mainly takes place in the peripheral zone, while the inner stresses remain negligible.…”

“…Brittle, respectively quasi-brittle, failure indicates a strong dependency of strength and size, commonly labelled size effects, first introduced by (Weibull 1939) and subsequently developed by his followers (Freudenthal 1968;Bažant et al 1991;Bazant 2005). Size effect based prediction of brittle bonds have since then been successfully formulated for, amongst other materials, fibre reinforced polymer (FRP) (Keller and Vallée 2006) and timber (Tannert et al 2012); and for axially loaded friction welded timber joints by Vallée et al (2011), respectively Hahn et al (2012).…”

“…Since the stress state is characterised by simultaneous occurrence of multiple stress components, the combined effect on the material strength has to be considered. Stress-based off-axis tests, successfully applied to two-dimensional studies on adhesively bonded double lap joints (Keller and Vallée 2006;Tannert et al 2012;Vallée et al 2011;Hahn et al 2012), present a convenient alternative to energy release based concepts commonly used (Balzani et al 2012;Pupurs et al 2013).…”

“…Weibull statistics have proven to be an accurate approximation for statistical modelling of brittle failure modes, which was successfully used in previous investigations on welded timber bonds (Vallée et al 2011;Hahn et al 2012). The cumulative distribution function for the Weibull probability of survival P s of a structural element can be expressed by Eq.…”

“…Although initially developed for isotropic materials failing under uniaxial loads, nothing in the derivations formulated for the Weibull theory limits its extension towards the considered orthotropy and multiaxiality. It has already been extended by Bažant et al (1991) towards main principal stresses; and subsequently several previous studies, including FRP and timber (Keller and Vallée 2006;Tannert et al 2012;Vallée et al 2011;Hahn et al 2012) did address this issue, and concluded that Weibull theory could be considered. Here, one normal stress vector r z , orthogonal to the surface, is combined with an in-plane shear vector s rz .…”