Analysis of the behavior of nailed timber frame shear walls through experimental tests and numerical simulations

In timber frame buildings, a good estimation of the performances of wall diaphragms assumes a great importance for a correct seismic or wind design, as the resistance and displacement capacity of the vertical resisting elements influence the distribution of horizontal forces. The paper focuses on the prediction, by means of numerical simulations, of the capacity curve of nailed timber frame shear walls subjected to in-plane horizontal actions. Non-linear static-analysis were performed assuming that the dissipative capacity of the panel is concentrated in the mechanical connections of the components (nails, hold-down, angle brackets). To assess the reliability of the numerical model, shear walls of different dimensions and connection arrangements were tested under in-plane horizontal cyclic loads. Comparisons between numerical and experimental results prove the validity of the model. Moreover it is evidenced that the distribution of the shear among the sheathing perimetric fasteners is affected by the application method of the steel connections at the base. In particular, when the hold down and/or the angle brackets are applied on the sheathing (not directly on the timber frame), the force distribution among the sheathing fasteners significantly differs from those suggested by the analytical methods proposed in the literature leading to erroneous predictions of the wall capacity. In these cases, the actual fastener orientation effectiveness has to be considered in the model for a correct prediction of the in-plane performance of the shear wall.