Recent advances on the prediction of the splitting strength of beams loaded perpendicular-to-grain by dowel-type and nail-plate connections

The splitting failure of timber beams loaded perpendicular-to-the grain by dowel-type or by nail-plate joints is a problem not well recognized by practising engineers. However this kind of failure, if not well understand in its main aspects, can lead to load carrying capacities considerable lower than the ones due to bending, shear or serviceability conditions. The paper presents concisely a new semi-empirical prediction formula for the splitting strength of beams loaded perpendicular-to-grain by both dowel-type and nail-plate connections. The formula is derived by means of a survey on the data of main experimental researches available in literature. However, it takes also into account the results of a recent parametric numerical study performed in the framework of linear elastic fracture mechanics by means of crack propagation analyses. The formula is initially derived for beams loaded by single-dowel connections and then modified by means of two correction factors to cover the case of beams loaded by multiple-dowel connections. Lastly, the correction factor related to connection depth is slightly modified to fit the experimental data of nail-plate connections which are characterized by a large number of punched nail rows. The prediction ability of the new semi-empirical formula is illustrated, discussed and compared with one of design equations adopted by the new European and German design codes for timber structures. Finally, a design proposal is simply derived and compared with experimental results.