Rods glued in engineered hardwood products

Abstract

Glued-in rods (GiR) represent an adhesively bonded structural connection widely used in timber engineering. Up to now, common practice largely focused on softwood. Most structural adhesives have been, accordingly, specifically formulated to perform on softwood, in particular spruce. The paper presents an overview over extensive research carried out with 9 adhesives, 3 engineered wood products (EWP), and 4 types of rods. Investigations started at component level, by fully characterising all adhesives, EWP, and rods. They were then extended to characterise the behaviour of interfaces, providing by this a methodology for selecting adhesives. Investigations at full scale followed, involving 5 different adhesives, 3 EWP, and 4 rod types; a total of 180 individual specimens were tested. Combining the material characterisation with finite element analysis (FEA), and reformulating strength in probabilistic terms, then allowed performing predictions of joint capacities for all 60 experimentally investigated GiR configurations. The comparison between predicted and experimental values showed a good agreement with relative difference amounting to-3% for beech glued-laminated timber (GLT), -2% for oak GLT, and +1%, respectively