Approximate Analysis of Framed Tube Structures for Static Parabolic Shape Lateral Loads

According to increase of population in cities, tall buildings and especially framed tube structures have been become interesting for structural engineers. Framed structure act primarily like cantilevered box beams and since they generally have much larger lateral dimensions than the internal shear wall cores, they are more effective in resisting the overturning moments of the lateral loads. However, due to flexural and shear flexibilities of the frame members, the basic beam bending actions of the framed tubes are complicated by the occurrence of shear lag, which could significantly affect the stress distributions in the frame panels and reduce the lateral stiffnesses of the structures. In this paper, a method has been adapted to study the shear lag coefficients for web and flange panels and for point, uniform distributed and triangular distributed loadings and then, the shear lag coefficients for the web and the flange panels are obtained for the parabolic shape lateral loads. Finally, by analyzing a 40-story framed tube structure under parabolic Shape lateral loading using this approximation method and comparing it with computer analysis, the error value in stress and displacement is estimated. The results of the research indicate that this method is suitable for the initial stages of the analysis and design of these types of structures.