ANALYTICAL APPROACH TO SEISMIC BEHAVIOUR ASSESSMENT OF RC FRAME STRUCTURES WITH RUBBER JOINTED MASONRY INFILL

Infilled structures are the most used type of structures in seismic-prone countries. Masonry infills are the most vulnerable part of these structures, even under medium-intensity earthquakes; hence, developing systems to prevent their failure to protect goods and human lives is crucial. Since current design codes are very advanced in reinforced concrete structures designs and there has been worldwide recognition of the importance of the infilled part of these structures, spotlight has been given to research and experimental and numerical analysis of behavior, seismic assessment and improvement of masonry infill – RC interaction. Recent experimental and numerical studies demonstrated that flexible joints in the infills or decoupling systems between the infill and the surrounding frame reduce the adverse effects of the frame-infill interaction on the ductility of the system. The main focus of this paper is to investigate the applicability and accuracy of a discrete macro element as a practical numerical tool for the design and assessment of RC masonry-infilled frames equipped with rubber joints alongside the frame. The model, implemented in OpenSees, can be represented by a simple equivalent mechanical scheme consisting of an articulated quadrilateral panel with a 1D diagonal link simulating the masonry shear deformability and eight 2D perimeter contact links governing the masonry axial and flexural responses and the infill-frame interaction. The analyses are conducted on a full-scale prototype subjected to shaking table tests conducted within the ERIES – FLEJOI project by a research group at the Institute of Earthquake Engineering and Engineering Seismology, Skopje. The experiment results and the numerical analysis show that these flexible joints aid in improving and balancing the structure’s bearing and ductility capacity and protect the masonry of pre-term damage. The comparisons between the numerical analyses and the experiments, presented in terms of displacement time histories and damage patterns, demonstrate that the macro-element can predict the complex non-linear dynamic response of the system with reasonable accuracy. Key words: infilled RC frame, rubber joints, discrete macro element, OpenSees.