Finite Element Modelling of RC Infilled Frame

Abstract

A comprehensive study has been conducted to evaluate the safety of existing masonry infilled RC reinforced concrete structures under earthquake loadings.The construction of reinforced concrete building with unreinforced infill or reinforced masonry is common practice even in seismically active countries. All buildings prior 1998 were constructed without seismic provisions while those constructed after this period adopted seismic codes. However, the codes have limited information on the design of infilled structures besides having differences in architectural requirements which may compound the structural problems. Although the influence of infill on reinforced concrete framed structures is known, the present seismic codes do not consider it due to the lack of sufficient information. From various research paper studies, it shows that the influence of infill on the structural performance is significant. The structural responses such as Fundamental period, roof displacement, inter-storey drift ratio, stresses in infill wall and structural member forces of beams and column generally reduce, with incorporation of infill wall. The structures designed and constructed with or without seismic provision perform in a similar manner if the infills of high strength are used.

To study the means and methods of modeling masonry-infilled RC structures, a comprehensive review of previous work and an analytical investigation is conducted. This thesis summarizes the results of those studies and verify on ATTENA, which specifically addressed the performance of RC frames infilled with unreinforced concrete masonry panels and subjected to in-plane lateral loading. The objective in modeling masonry-infilled frames has always been to develop a simple model that would capture characteristics of the masonry. Achieving this objective requires understanding the behaviour in more detail. The only feasible approach for simple and accurate modeling is to identify relevant parameters and employ numerical simulation, using well-calibrated analytical and experimental models to replace most of the expensive physical modeling. The aim here is to identify such numerical finite element models, demonstrate their capabilities, and facilitate the use of those models by identifying a commercial finite element analysis program having similar capabilities. The finite element models identified are a cohesive interface model to simulate the behaviour of mortar joints between masonry units and the frame/panel interface, and a discrete element approach to model the concrete. Analytical verification studies were carried out to determine the capabilities and limitations of the models.