AN INVESTIGATION OF SHEAR-LAG IN FRAMED-TUBE BUILDINGS

Abstract

Shear-lag is major problem in framed-tube buildings. Like in box-girders, T-beam, etc., unequal straining of longitudinal fibres of flanges leads to unequal stress distribution, which is called shear-lag. In an ideal vertical cantilever tube, having infinite shear stiffness, subjected to lateral loading, produces uniform stress distribution in flanges and linear stress distribution in webs. But when shear deformations are considered then stress distribution are not same as that of pure tubular action. Similarly in an ideal framed tube building if spandrel beam has infinite bending stiffness which produces equal axial stress distribution in all columns in flange frame and linear stress distribution in web frames. In actual scenario spandrel beam bends and axial stress distribution doesn’t remains same as compared to ideal case. Framed-tube building subjected to lateral load possess positive and negative shear lag. The level of shear lag reversal depends on loading type and location. Due to this shear lag, slab diaphragm bends out-of-plane and loads comes on secondary structural elements and partition walls.