Abstract:
In thc building construction, framcd structurcs are frcquently used due to ease of
construction and rapid progrcss of work. Column and girder framing of reinforced
concrete structurcs is in-fillcd by masonry infill pancls, solid or hollow blocks or concrete
blocks. Masonry infill panels havc bccn widely used as interior and exterior partition
walls for aesthetic rcasons and functional nccds. Usually in analysis only the bare frame
is modeled ignoring the cffect of infills with the assumption that such modeling is rather
conservativc and computationally more cfficicnt. However such assumption may lead to
substantial inaccuracy in prcdicting the latcral stiffness, strength and ductility !Jf a
structure. When an infillcd framc is subjccted to lateral loading, the' infills behave
effcctively as struts along its compression diagonals to brace thc frames. When infill
walls arc omittcd in a particular storcy, a weak storey is formed compared to much stiffer
other storeys. The ground floor is the most common location, which is usually devoid of
infill component due to parking or largc commercial spaces, thus resulting in a point of
weakness in the structure.
Normally in structural analysis it is considered that the Equivalent Static Force Method is
more conservative than more rigorous dynamic procedure for regular structures or
structures of smaller height. Thc present study compares the results of Equivalent Static
Analysis and the Response Spectrum Analysis of frames modelcd with infills. In this
investigation the performancc of masonry infill componcnts on frames under different
conditions have been studicd. The masonry infill has been modeled by equivalent struts.
The size, shape and other propertics of thc equivalent struts have been calculated using
different published litcrature. Thc drift and flexural behavior of the frame with different
combinations of infill walls have been studied and compared using both the Equivalent
Static Analysis and Response Spectrum Analysis techniques. A parametric investigation
has also been performed varying various parameters of the frames to observe their
influences in drift and flexural behaviour of the frames. The present study is aimed at
finding out the effect of infills on structures due to horizontal loading, which would lead
to safe, economic and durable framed structures against earthquakes. It is observed that the Equivalent Static Analysis shows higher values for deflection and
moment than the Response Spectrum Analysis only for the bare frame. Presence of infill
in the frame, however, shows converse results for 6, 9 and 12 storied frames. For 4
storied frames, Response Spectrum Analysis gives higher values for both deflection and
moments for the structures with or without infill components than the Equivalent Static
Analysis. It is observed that moment increased depending on the increase of the infill
percentage. When all bays have infill it shows the highest variation of maximum moment
and conservative results are shown by the Response Spectrum analysis than the
Equivalent Static one.
