In reality, because of requirements of commercial
or residential uses, many buildings become vertically irregular. A structure
with irregular distribution of stiffness along the building height is
classified as vertical stiffness irregularity. Change in size of beams and
columns in the specific stories compared to other stories to fulfil functional
requirements of structure and for other commercial purposes are the example of
stiffness irregularity. The past earthquakes data show that the seismic responses
of vertically irregular buildings can be signi?cantly different in comparison
to the regular structure. Therefore, conventional analysis methods, which are
often used for regular buildings, may be unable to predict the behavior of
irregular buildings with an acceptable accuracy.
Many researchers has shown interest in the
area of study of vertically irregular buildings. Al-Ali and Krawinkler (1997)
has studied the seismic response of vertical irregular one bay frame structure
in terms of elastic and inelastic dynamic analysis. Chintanapakdee and Chopra
(2004) has done comparative study on response of vertically irregular and
regular frame building using non-linear response history analysis and they also
investigated the accuracy of modal pushover analysis. Michalis et. al. (2006) presented methodology
based on incremental dynamic analysis (IDA) to study the effect of vertical
irregularities on the seismic performance of multi-story building. Karavasilis et. al. (2008) made extensive analytical
parametric study to examine and evaluate the seismic inelastic response in
steel moment resisting frame with vertical mass irregularity. Kashkooli and
Banan (2012) investigated the effect of frame setback irregularity in height on
accuracy of modal pushover analysis for predicting target displacement, story
drift and base shear. Varadharajan et.
al. (2013) have reviewed the research work done in the past in the area of
structural irregularities and different types of modelling approaches used.
Shelke and Ansari (2017) made comparative study on vertical irregular and
regular RC structure using response spectra analysis.
The main objective of this paper is to evaluate
the seismic response of vertical stiffness irregular frame subjected to
earthquake ground motions corresponding to seismic hazard level of 2%
probability of exceedance in 50 years. Seismic responses are shown in terms of floor
displacement and height wise distribution of story drift. To achieve this,
building frame model is introduced with irregularity at three different
location using single modification factor. Comparative study is made to
understand behavior of regular and irregular frame structure under same set of
earthquake ground motion.