NUMERICAL MODELS FOR THE NON-LINEAR IN-PLANE BEHAVIOUR OF TRADITIONAL UNREINFORCED AND REINFORCED TIMBER FLOORS

Traditional timber floors are usually characterized by a very low in-plane stiffness and they often need to be reinforced to improve the seismic performance and to obtain a global “box behaviour” of the building. In a recent research project, cyclic tests were carried out to assess the effectiveness of different timber-based, dry-connected, strengthening solutions for the in-plane retrofit of timber floors. The tested techniques use CLT and OSB panels connected to the timber joists and planks. These interventions are reversible and minimally invasive and are characterized by low mass and low thickness. The tests showed a significant increase in shear strength and stiffness of the reinforced floors with respect to the unreinforced ones. In this paper, two numerical models to describe the in-plane behaviour of the timber floors are presented. The models allow to simulate the non-linear cyclic behaviour of unreinforced and reinforced floors. In particular, the stiffness and strength decreases due to the cyclic action are properly taken into account. The first model is more detailed and is addressed to investigate the role of the different parameters as geometry, fastener stiffness and spacing, sheathing thickness and orientation, opening location, which determine the global floor behaviour. The second one allows a simple and relatively fast modelling of the unreinforced or reinforced floor which can be used in a global model of a building thanks to the lower computational cost. It uses constitutive laws commonly available in many commercial finite element software. Both the proposed models are calibrated and validated on the basis of experimental results