Experimental analysis of brittle failure in Timber-to-steel connections with small diameter fasteners loaded parrallel-to-grain

An experimental test campaign of timber-to-steelconnections with small diameter fasteners loadedin tension parallel-to-grain has been conducted inorder to study brittle failure (plug-shear). Differentmaterials (timber -GL28h and LVL80S- and fasteners-nails and screws-) and geometries are combined toidentify the main parameters that have an influenceon the load-carrying capacity of the connection.The obtained test results confirmed plug shear as themain failure mode. It is noticed that the failure ofall the loading planes does not happen at the sametime:first, the lateral shear planesL are activated;and then, only if the connection is able to withstandmore load, the head tensile H and the bottom B shearplanes fail.Regarding the ductility Df, both brittle and mixedfailure are reached. The least brittle cases usuallycorrespond to configurations that combine screwswith GL28h. Configurations with screws combinedwith LVL80S usually reach both the highest averageload-carrying capacity and stiffness values.The analysis of the test results provides informationon the influence of different parameters. Some ofthem are confirmed to have an influence (such astimber product, fastener type, spacings, fastenerslenderness, or the pre-drilling of the holes), whileothers seem not to have a clear influence (steel platethickness and timber thickness).Finally, the comparison of the test results with thepredicted values from the existing models dealingwith plug-shear helps to identify some aspects tobe improved. With all this new knowledge, furtherwork would try to provide a new model which couldimprove the prediction accuracy by including theanalysed influencing parameters.