Experimental or theoretical tests show that dramatically changes of infill area causes soft story mechanism.
“Soft story” mechanism is the most frequent failure mode of reinforced concrete (R.C.) structures. This phenomenon is
caused by the fact that the overall shear force applied to the building by an earthquake is higher at the base floor. If the
lower story is not originally weakened, it is however there that infill are the most stressed, so that they fail first and create
the weak story and finally leads collapse of structures. This kind of collapse was observed many times in Turkey caused
by earthquake. The aim of this paper is to show the contribution of infill walls to the building response during earthquake.
Different type of configuration of infill walls are modeled and analyzed by the Finite Element Method. These models also
have soft story risk. The nonlinear force-displacement behavior is used for structural analysis. El Centro N-S component
is used for time-history analysis.