NON-LINEAR ANALYSIS OF INFILLED FRAMES

Abstract

Unreinforced masonry in fills has long been known t o affect the strength and stiffness of frame. Under the action of a lateral load the principal compressive diagonal acts as a strut or b racing and increases the initial lateral stiffness of the framed structure. However, in the presence of openings in walls, which is more practical, the behavior of infill changes. The primary objective of this paper is to study the variation of lateral stiffness, principal compressive diagonal strut width with modulus of m asonry infill, with and without openings. In the study a non-linear (multi-linear) analysis is performed, since it is more realistic. From the analysis performed using ANSYS Version 10.0 it is seen that linear analysis over-estimates the lateral stiffness of the infill frame. Further, it is observed that the width of compressive diagonal generally decreases w ith increase in the modulus of masonry. It is also seen that incase of two frames with equal area of openings, the frame with larger width of opening exhibits slightly more initial lateral stiffness due to possibility of formation of single diagonal strut.