Research on the Vertical Setback Problem of Steel Bundled Tube Structure

To study the mechanical performance of steel bundled-tube structures and find the reasonable setback scheme, the 18 calculation model with different setback based on the same bottom, height as well as the volume were designed. The effect of different setback methods on performance indexes such as natural vibration period of the structure, stiffness was analyzed. Stress total enhancement ratio and reference enhancement ratio are introduced to study the distribution rule of the spandrel beam stress under different vertical setback methods. The distribution rule of column stress was also analyzed. The results show that the changing rule of the equivalent wind effect coefficient is the same as the basal shearing force and basal anti-overturning moment. Reference enhancement ratio of the spandrel beam is a fixed value at a certain height and volume. Total stress enhancement ratio of the spandrel beam is mainly related to the remained height. Vertical setback causes abrupt stress in the columns. The setback influence on the columns is less than that on the beams, and the abrupt stress stories are also less. It is advised that the location of the initial setback should be as far as possible from the embedded end. The reasonable setback method should be uniform and symmetric.