INFLUENCE OF DENSITY AND PREDRILL IN THE EMBEDMENT STRENGTH OF TWO HARDWOOD SPECIES

The embedment strength is a key parameter in the design of timber connections with metal fasteners. It can be determined by the equations given by Eurocode 5 from the density value. Since those equations were mainly developed for softwood species, the objective of this work is to evaluate the influence of the density in the embedment strength of two high- and low-density hardwood species (beech – Fagus sylvatica- and poplar – Populus x euroamericana- , respectively) in the parallel- and perpendicular-to-grain direction. Four different experimental test configurations were carried out according to EN 383 for each species using a 5-mm nominal diameter and considering the influence of predrilling in the wood specimens. Results showed a good correlation between density and embedment strength for all the test types. In addition, predrilling showed no significant influence on the value of embedment strength, contrary to what is considered in the equations provided by the current version of the structural design codes. Both, current and new equations proposed by the new draft of Eurocode underestimate the values of embedment strength in both species, thus being on the safe side for the structural design of connections.