| Summary: | Development of technology facilitates construction of tall buildings. One of the common kinds of them is Tubular systems, divided into different types: framed tube, tube-in-tube, trussed tube and bundled tube systems. The main problem of tubular systems is the shear lag phenomenon that decreases the bending rigidity and moment resistance of the structures. In this paper, the phenomenon of shear lag in all kinds of steel tube systems is investigated analytically. In order to reach this objective, sixteen steel multi-storey tubular structures with the same plan, but a with a different number of stories and different tubular systems were designed by ETABS software based on AISC. Then the shear lags of each structure in different elevations are calculated by using the linear response spectrum analysis. The results show that nearly in the upper half of the structures the negative shear lag happens. Besides all, the formula was derived for each system with regard to the analyses data with linear regression examine by SPSS software, which showed that there is a significant relation between shear lag and three independent variables: story number, height ratio and distance from the web of the structures.
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