Structures built with cross laminated timber (CLT) are an attractive alternative to traditional construction materials in terms of environmental performance and habitability, but its structural behavior is not well understood for each timber specie. This work provides a comprehensive study of the structural behavior of radiata pine CLT shear walls, by means of laboratory testing and numerical analysis of hold down connections. The observed test response of connections is replicated by calibrating two hysteretic models on OpenSees, and its fidelity is revised through the analysis of a full scale wall test and simulation. Main outcomes suggest that advanced modelling tools can accurately reproduce the hysteretic behaviour of the connections of timber panels. In terms of connections behaviour, it is observed that hold downs on radiata pine CLT elements reach less load capacity than hold downs on other wood specie, and no significant difference with the parallel to grain capacity of angle brackets connections is noticed. Besides, it is found that radiata pine CLT walls can achieve suitable cyclic loading performance and reach high levels of displacement ductility. Furthermore, the importance of friction on the load capacity of the wall is showed.
The mechanical behaviour of steel-to-timber joints with annular-ringed shank nails is investigated using numerical modelling and a component approach. These joints are used in Cross-Laminated Timber (CLT) buildings to anchor metal connectors such as hold-downs and angle brackets to the timber panels. At first, a general hysteresis model is introduced, where a single fastener joint is schematized as an elasto-plastic beam embedded in a non-linear medium with a compression-only behaviour. A second hysteresis model is then presented, where the mechanical behaviour of the joint is simulated by a non-linear spring with three degrees of freedom. Both models are calibrated on the design rules prescribed by the reference standards. Moreover, average strength capacities are determined from the corresponding characteristic values assuming a standard normal distribution and suitable coefficients of variation. As first applicative examples of the proposed models, shear tests are simulated on single steel-to-timber joints with annular-ringed shank nails and on a connection made of an angle bracket and sixty nails. The scatter of mechanical properties in steel-to-timber joints is also taken into account in the simulations and a stochastic approach is proposed, demonstrating acceptable accuracy.
