BEHAVIOR OF REINFORCED CONCRETE FRAME WITH SHORT COLUMN EFFECT UNDER LATERAL CYCLIC LOADING

In this paper an attempt was made in reinforced concrete structures where windows or door openings have been left in the infill walls due to architectural necessities. The columns with partial infill has been damaged seriously during the past earthquakes due to short column effect and this type of column leads to major failure of structure during earthquake. The behaviour of such columns is not known fully. This paper investigates analytically the behaviour of short column under cyclic lateral loading. The aspect ratio of infill wall (Lw/Hw, where Lw = infill length, Hw = infill height) and its placement configurations were the parameters of the analytical study. The behaviour of the three short columns in the frame with different aspect ratios were studied for load displacement hysterisis curve, stiffness degradation, ductility ratio, Von Mises Stress and crack pattern. Test results indicates that when the aspect ratio of the infill was increased, the lateral strength and rigidity increased and at the same time displacement and ductility of structure were decreased. In addition to this, crack pattern results indicates that in the bare frame without infill, initial cracks are developed at the beam column joint and at the ultimate load level, a series of wide cracks are developed at the support which makes the structure instable and leads to failure. In the partial infill frame, cracks are developed at the junctions of beam column and masonry infill. Nominal cracks are developed at the support since the portion below is completely restrained by the tight fitted masonry infill. So this tends to the formation of short column effect in the frame member with partial infill, which leads to major collapse.