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. Axial force in exterior columns is unequally distributed due to the flexibility of circumferential beams. This phenomenon is called shear lag which reduces the efficiency of the above system. In this research the earthquake behavior of reinforced concrete framed tube structures in three different plan shapes, including Rectangular as the control model, Triangular and Hexagonal, is investigated. Also Iranian code was used to reload structures in this paper. It is observed that, structures with Rectangular plan shape had the maximum amount of shear lag and the Hexagonal ones had the minimum.