Seismic behaviour of RC frames with uncoupled masonry infills having two storeys or two bays

Abstract

Reinforced concrete (RC) structures with masonry infills are widely used for several types of buildings all over the world. However, it is well known that traditional masonry infills constructed with rigid contact to the surrounding RC frame performed rather poor in past earthquakes. Masonry infills showed se-vere in-plane damages and failed in many cases under out-of-plane seismic loading. As the undesired interac-tions between frames and infills changes the load transfer on building level, complete collapses of buildings were observed. A possible solution is uncoupling of masonry infills to the frame to reduce the infill contribu-tion activated by the frame deformation under horizontal loading. The paper presents numerical simulations on RC frames equipped with the innovative decoupling system INODIS. The system was developed within the European project INSYSME and allows an effective uncoupling of frame and infill. The simulations are car-ried out with a micro-modelling approach, which is able to predict the complex nonlinear behaviour resulting from the different materials and their interaction. Each brick is modeled individually and connected taking in-to account nonlinearity of a brick mortar interface. The calibration of the model is based on small specimen tests and experimental results for one bay one storey frame are used for the validation. The validated model is further used for parametric studies on two storey and two bay infilled frames. The response and change of the structural stiffness are analysed and compared to the traditionally infilled frame. The results confirm the effec-tiveness of the INODIS system with less damage and relatively low contribution of the infill at high drift lev-els. In contrast to the uncoupled system configurations, traditionally infilled frames experienced brittle failure at rather low drift levels.