Ductile End Connections for Glulam Beams

Ductility, which is the capability of a structure to deform significantly beyond the elastic limit without brittle failure, is a fundamental property which can be an important requirement in many instances. In particular, the behaviour of structures under seismic actions depends on the capacity to withstand large displacements in the plastic field without reaching the collapse. Wood suffers from the unfavourable material characteristic that exhibits no (tension) and limited (compression) post-elastic deformation capacity. Therefore timber structures rely on steel dowel-type connections to provide ductility and energy dissipation. In general, good performance can be achieved by light timber structures with a large amount of steel connectors, designed to favour steel yielding as the governing mechanism. For heavy timber structures, because of the lower redundancy of the structure, a more "engineered" joint design is needed to ensure a safe performance during seismic events. The research reported in the present paper has been devoted to the investigation of an innovative steel-to-timber joint suitable for different joint configurations within a frame, where a timber element is connected to a steel stub by means of an end-plate and glued-in steel rods. The proposed system has been investigated by means of numerical models and experimental tests, in order to determine strength values and moment-rotation relationships of the joint. Some interesting conclusions can already be drawn from the available experimental tests, suggesting a possible full implementation of such techniques in seismic resistant timber structures, which is the ultimate goal of the research.