Equivalent Strut Width for Partial Infilled Frames

Abstract

The usual practice in the analysis of reinforced concrete frame structures is to analyze the frames with skeleton members comprising of only slabs, beams and columns. However, in reality the structures also possess masonry infills within most of the frames, but they are ignored in the models so as to minimize the computational works. Researchers have indicated that the frames comprising of masonry panels behave significantly stiffer as compared to bare frames. The infills contribute in stiffening the frames, but researches also show that the partial infills can cause adverse effect known as captive column effect. A lot of experimental evidences show that the captive column effect causes the partially infilled frames to damage during earthquakes. It is still a matter of interest to researchers to find out how much shear actually occurs at the location where the wall terminates. The shear force generated at the points where the wall terminates within the frame in the windward side causes the windward side column to fail. This study is done to identify the shear force values at such locations through analytical formula. The equivalent strut width as provided by various researchers is compared with the established formula for verification and further applied to obtain the shear forces at various locations in partially infilled frame. Equivalent strut width formulation is done in this paper, which may be used directly in the frame analysis wherever partially or fully infilled walls are provided. In the analysis of Reinforced concrete framed structures, there is a trend of ignoring the existence of brick infill mainly due to the reasons of complicated computations. Only the frame is considered in the analysis, which actually saves tedious calculation time and effort, but the real existence of bricks within the frames being ignored, actually underestimates the capacity of the structure. From the past studies done by various researchers, it has been found that the brick infills actually contribute in enhancing the strength of the structure by resisting the lateral deflection of frames applied to horizontal forces. Again, the contribution has been felt primarily during the earthquake events, where, most of the infilled framed structures remain less damaged as compared to the frames which are left bare. It is also necessary to examine whether the contribution of infilled frames remain equally good when some openings are provided within the panels. Some past studies also have indicated that the infills which include voids tend to be less effective, although, better than with the bare frames. The contribution of brick infill has been studied in this paper, particularly for partially infilled one because, the partially infilled frames in the past earthquakes have shown damaging