Nonlinear Static Analysis of Masonry Infilled Frames with Open First Floor

Abstract

Reinforced concrete frames with masonry infill are often used structural systems throughout the world, especially in developing countries and countries around Mediterranean region. Masonry infill is characterized with significant in-plane strength and stiffness and it can greatly alter the response of structures exposed to seismic loads. Irregular distribution of infill in plane and along building height can lead to series of unfavourable effects (torsion effects, dangerous collapse mechanisms, soft or weak storey, variations in the vibration period, etc.). In order to investigate the influence of irregular distribution of masonry infill on the behaviour of structures exposed to seismic loads, an extensive nonlinear static analysis was performed. Six reinforced concrete frames with different number of storey, designed as bare frames were analysed. In the phase of assessment, all structures were upgraded with the masonry infill panels in all storeys except the first one. Masonry infill was defined with two different strength and stiffness characteristics. The obtained results, expressed in terms of the comparison of damage pattern, capacity curves and stiffness degradation shows significant influence of masonry infill on the strength, stiffness and ductility of analysed frames.