Investigation On The Influence Of Infilled Wall On The Seismic Performance Of Reinforced Concrete Frame Structures

Structural frames are often filled with infilled walls serving as partitions. theinfills usually are not considered in the structural analysis and design. since infillsare not included in conventional structural modelling and analysis for the purposesof seismic design, their contribution to the lateral stiffness and strength, ifsignificant, may invalidate the analysis and, furthermore, the proportioning ofstructural members for earthquake resistance on the basis of its results as well.infills may fail in a rather brittle fashion, giving rise to irregularities in the strengthand stiffness of the structure and possibly formation of a soft storey. Therefore, it iscrucial to understand the contribution of infill walls to earthquake response of framestructures.Two different approaches were used to to solve the complicated problem ofinfilled frames. The first method treats the masonry filler walls as diagonal struts,and the second method use the finite element method to incorporate filler walls inanalysis. In the present study, several typical diagonal strut models are compared andanalylized.Of all the methods of analysis available, the finite element method is the mostpowerful one. It can accommodate all the variables like different material properties,complex nature of stress system existing at the interface of infill and frame,separation, slip and loss of friction at the interface. In this paper, a simpler iterativefinite element method of analysis making use of the ANSYS computer programpackage is described and has been utilized for the analysis of infilled RC frameswithout openings.The effect of infill walls on seismic behavior of three sample frames withdifferent infill arrangements was investigated. The diagonal strut approach isadopted for modeling masonry infill walls. Pushover curves are obtained for thestructures using nonlinear analyses option of commercial software SAP2000. Fromthe pushover curves, story displacements, relative story displacements, maximumplastic rotations are determined. Regarding with the analysis results, the effects ofirregularities are determined in the structural behavior under earthquake.