1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

Infill walls significantly affect the resistance of structure. However, in the design it is generally neglected which leads to erroneous assessment of stiffness, load bearing capacity and serviceability. Seismic response of reinforced concrete frames with masonry infill can be analysed employing models of different complexity: micro-, meso- and macromodels. Macromodelling strategy, where masonry infill is represented by homogenized orthotropic continuum, requires low computational effort and basic material information without losing accuracy of global structural behaviour. Highly nonlinear behaviour of RC frame and masonry infill as well as their mutual interaction was modelled using quadratic membrane elements in DIANA FEA. Total strain rotating crack constitutive model was used for concrete, von Mises for embedded rebars and engineering masonry model for hollow infill. Mohr-Coulomb contact elements with gapping, applied at the interface between frame and infill, had significant influence on the structural response. The sensitive interface properties were calibrated after experimental tests which included masonry infilled frame with and without opening as well as bare frame. In order to match the response of the model and the experiment, it was necessary to model friction between rollers and the columns using bilinear springs. Cyclic static loading was imposed on the structure under constant vertical precompression. Failure modes pertain to crushing of infill corners and gradual separation of brittle masonry from the frame which further leads to formation of diagonal strut. The development of damage in the reinforced concrete frame and masonry infill according to the EMS-98 scale is described and recommendations for numerical modelling are given.