New anchoring system with adhesive bulbs for steel rod joints in wood

Joints with threaded rods glued in wood are a technique of great interest for both new projects and the restoration of old structures. Our research team has developed a comprehensive study, both theoretical and experimental, on joints for different types (sawn and laminated) and species (conifers and deciduous) of wood. This article shows the new system developed to improve anchoring efficiency. The new system involves a widening in the bore that is filled with epoxy adhesive, which creates a bulb that can increase the load capacity of the anchorage and the ductility of the joint. The types of bits designed to create the inner bulb easily are likewise detailed. The article also shows the results of the experimental work performed, comparing the load values and failure modes of this type of joint with the traditional system of straight anchoring.

► We have developed a new anchorage system of rods glued in timber using adhesive bulbs.
► We have designed various drills that allow to carry out the inner enlarging of the holes with great easiness.
► We have carried out an experimental study comparing the traditional straight system and the anchoring with bulbs.
► The adhesive bulb system increases meaningfully the load capacity of the joint.
► The adhesive bulb system allows to get ductile joints using very small anchorage lengths.