Ductility of large-scale dowelled CLT connections under monotonic and cyclic loading
In the last decade, several tall timber buildings have been constructed in Europe, North America and Australasia. Often engineered wood products such as Cross Laminated Timber (CLT) are used in combination with strong connections to construct timber buildings exceeding 10 storeys. For tall timber buildings located in seismic areas it can be challenging to design strong yet ductile hold-downs in CLT shear walls. One common solution is to use dowelled connections with inserted steel plates. Design code calculation rules for timber connections are usually derived from smallscale testing assuming that strength and ductility properties can be extrapolated for larger connections in actual buildings. For CLT connections, fastener spacing requirements are derived in a similar manner under the general assumption that brittle failure modes can be prevented due to the reinforcing effect of cross-layers in CLT. In order to assess the validity of these assumptions, experiments were conducted on different layouts of small-scale and large-scale dowelled connections in CLT, Laminated Veneer Lumber (LVL) as well as a LVL-CLT hybrid, all made out of New Zealand Radiata pine. The tests comprised of 40 small and 12 large samples subjected to monotonic and cyclic loading. Strength and ductility were compared between the different connection sizes and layouts. For the large-scale connections, particle tracking velocimetry (PTV) was used for the first time to measure displacements.