Loading rate effects on embedment properties of dowel-type fasteners in laminated veneer lumber (LVL) and glued laminated timber (GLULAM)

In timber engineering. embedment strength represents the resistance developed by the timber against localized bearing stresses generated by a dowel-type fastener. This property is a key input for determining the design capacity of timber connections and is included in major timber design standards, such as CSA O86, Eurocode 5, and NZS AS 1720.1. This study experimentally evaluates the embedment strength response of dowel-type fasteners inserted in softwood laminated veneer lumber (LVL) and glued laminated timber (Glulam) under loading rates associated with earthquake and progressive collapse events, aiming at providing essential data to design connections under such dynamic loadings. An experimental programme consisting of 640 full-hole embedment tests was performed in accordance with European standard EN 383. Tests were conducted on samples prepared with ⌀12 mm and ⌀16 mm dowels, loaded both parallel and perpendicular to the grain under four loading rates, inducing failure from 200 s (quasi-static) to 0.2 s. Elastic stiffness, yield stress, embedment strength, and ductility were determined for each test. For the LVL specimens, the average embedment strength increased by 17.9–25.4%, while for the glulam specimens, it increased by 10.0–31.9% as the failure time decreased from 200 s to 0.2 s. The increase in embedment strength was found to be independent of the material type, dowel diameter and loading orientation. A rate-dependent relationship equation was proposed and indicated an increase of 15% in the characteristic embedment strength between quasi-static loading and failure developing in 0.2 s. Inputting this outcome in design equations predicts an increase of about 15% in full connection capacity.