Behavior of masonry-infilled concrete frames subjected to lateral loads

Abstract

Konstruktionen aus mauerwerksausgefachten Stahlbetonrahmen sind überall auf der Welt häufig anzutreffende Bauelemente. Früher wurde die Ausfachung im Allgemeinen als nichttragende Elemente behandelt. Die vergangenen Erdbeben (wie z. B. Türkei, Bam und China) haben gezeigt, dass die Ausfachung von Rahmenkonstruktionen das Trag- und Verformungsverhalten deutlich beeinflussen kann. Die Beobachtung von negativen und positiven Effekten der Ausfachung, hat dazu geführt, das Verhalten von Rahmenkonstruktionen mit Berücksichtigung der Ausfachung zu untersuchen.<br />Das Hauptziel dieser Arbeit bestand darin, unter Verwendung des FE-Programmes Atena ein Modell zu entwickeln, in dem das Verhalten von Stahlbetonrahmen mit Ausfachungen aus Mauerwerk besser beschrieben werden kann. Durch die Verwendung des FE-Programmes ist es möglich, die nichtlinearen Struktur- und Materialeigenschaften von Mauerwerk abzubilden und Einflüsse von verschiedenen Parametern auf die Tragfähigkeit zu quantifizieren.

Infilled frame constructions have been in use for more than 200 years. Masonry infills have often been treated as nonstructural elements and their structural presence is often ignored by engineers. The infill panels may interact with bounding frames when the structure is subjected to strong lateral loads induced by seismic load. Such interaction shows some positive and negative effects of the structure and has been a subject of many debates. The previous experimental results demonstrated that the masonry infill walls benefit the buildings due to the amount of increase in the initial stiffness of reinforced concrete frames. On the other hand, infill walls have been related to failures, such as the development of soft stories and the brittle shear failure of columns induced by short-column effect.<br />During the last 50 years, a number of different analytical models (micro- and macro-models) have been developed to evaluate infilled structures under in-plane and out-of-plane horizontal dynamic actions.<br />All studies have shown that the behavior of an infilled frame is heavily influenced by the interaction of infill with its bounding frame. The finite element analysis may be the most powerful tool for evaluating the behavior of infilled frames, and such models are able to provide better predictions of the behaviour of infilled frames. In this study, two different numerical modeling techniques are used (simplified micro-modeling and macro-modeling) and the results of FEA analyses (pushover analysis) are compared for these two idealizations.<br />Furthermore, a parametric study has been conducted to examine the influence of the geometry and material parameters on the numerical results and indentify the important modeling parameters. Finally, a simplified method based on diagonal spring is described for infill wall here to assess the maximum lateral strength of reinforced concrete infilled frames.