Out-of-plane loaded masonry walls retrofitted with oriented strand boards: Numerical analysis and influencing parameters

The computational prediction of the out-of-plane behaviour of unreinforced masonry walls is a challenge. However, computational numerical models may provide, if properly calibrated, a powerful tool to predict the behaviour of new retrofit techniques. This paper presents the Finite Element (FE) modelling of masonry walls retrofitted with oriented strand boards (OSB) aiming the prediction of its out-of-plane behaviour. Such retrofit measure has been proposed by the authors for brick masonry walls and its efficiency has been demonstrated through experimental studies on small-scale and larger-scale masonry specimens (out-of-plane monotonic tests). The data gathered in the experimental phase has been used here to calibrate the numerical FE-based models (i.e. non-retrofitted and retrofitted). For this purpose, a detailed micro-modelling strategy has been followed assuming a perfect bond between mortar joints and brick units. The so-called Concrete Damage Plasticity (CDP) model has been adopted to describe the constitutive relation of the masonry and the OSB timber panel. The connection between the masonry and the OSB panel has been modelled through elastic anchors. Numerical results show a good agreement with the experimental data, in terms of observed damage pattern and capacity curve (within 10% difference). The calibrated numerical model has been instrumental in developing a parametric analysis to study the effect of different OSB thicknesses, the side of the application of retrofit, and the spacing between connections through anchor rods. These revealed that the out-of-plane capacity of the system is directly proportional to the OSB thickness and that the spacing between steel connectors should be lower than 500 mm for an adequate response.