Coupled shear-tension numerical model for modelling of CLT connections

A new numerical model able to account for the interaction between tension and shear forces on typical hold-down connections used in CLT structures is proposed and discussed, starting from results of an experimental campaign conducted at University of Bologna. A specifically developed method appropriate to evaluate the main strength and stiffness parameters from the experimental cyclic force-displacement curves is presented, and the corresponding trilinear backbone approximation is defined. Parameters obtained from tri-linear backbone curves were used to define the effect of the tension-shear interaction on the behaviour of hold-down connections, particularly as far as yielding and peak strength and stiffness parameters are concerned. In order to numerically reproduce the behaviour of connections, a coupled zero-length element is developed and presented. The model is implemented in OpenSees and adopted to model single connection element. The model is calibrated referring to experimental results of specimens loaded only in tension. Then the model is validated referring to tests with increasing level of tension-shear interaction. The proposed model is able to reproduce the actual behaviour of hold-down connection with coupled tension-shear forces under monotonic load conditions. Finally, a first proposal for accounting the hysteretic behaviour is presented, and some preliminary results are shown.