Abstract—Framed tube structural system, proposed by “Fazlur khan” is one of the most influential systems in design and construction of skyscraper. The tubular system in its simplest form, consists of closely spaced exterior columns linked at each floor level with relatively deep spandrel beams. Due to the flexibility of circumferential beams, axial force in exterior columns will be unequally distributed. This phenomenon is called shear lag which reduces the efficiency of the above system. In this research the behavior of reinforced concrete framed tube structure has been studied through three different plan shapes including Rectangular as the control model, Triangular and Hexagonal subjected to earthquake load. Also Iranian code [1] was used to reload structures in this paper. It is observed that, structures with the Rectangular plan shapes had a maximum of shear lag and the Hexagonal ones had a minimum.
