Structural Arrangements And Mechanical Performance Of High-rise Twisted Diagrid Tube Structures

As a new type of structural systems, twisted diagrid tubular structures attainattributes of beautiful shapes, reliable structures, and practical functions. Its proposalcan effectively promote the application of tubular structures in twisted high buildingsand the innovation of design and construction. This paper mainly focuses on lateralresistance and mechanical performance of such structure type with different geometricparameters and various structural plans.The general structural arrangements of twisted diagrid tubular structures wereillustrated according to structural efficiency and lateral resistance. The sensitivities ofthe lateral stiffness of this structural type to relevant factors were evaluated, includinggeometric parameters such as story rotation angle, distance between two adjacent ringbeams, and height-to-width ratio, i.e. aspect ratio of the building, along with structuralplans. Elastic response spectrum analysis was carried out for a series of structuralmodels. Rotation angle and height-to-width aspect ratio are dominant while the distancebetween two adjacent ring beams is of little influence. The distance between twoadjacent ring beams is related to angle of diagonal bracings, which is recommended tobe45degrees, and can be mildly adjusted to meet the requirements of construction andaesthetics. There is a suitable range of story rotation angle responding to the maximumlateral stiffness, which narrows with the increase of aspect ratio. Out of the range, thetwisted structures are inferior to the traditional structures in terms of lateral stiffness.When the accumulative rotation angle at the top reaches90degrees, structures withdifferent aspect ratios and structural plans all achieve the optimal stiffness. With theincrease of side number of the polygonal structural plan, the sensitivity of the lateralstiffness related to the accumulative rotation angle decreases, and the twisted structuresbecome closer to the traditional ones in the lateral stiffness point of view.A series of structural model analysis was carried out to evaluate the sensitivity ofmechanical performance of this structure type to some related factors. The accumulativerotation angle has a remarkable effect on spiral columns and diagonal bracings. With theaccumulative rotation angle increasing, the axial forces of spiral columns decrease whilethe axial forces of diagonal bracings increase. Compared with the traditional structures, twisted structures can efficiently reduce the moments of spiral columns and diagonalbracings，and distribute the axial forces reasonably. With the increase of side number ofthe polygonal structural plan, the sensitivity of structural changes in force magnitudes tothe accumulative rotation angle decreases. Under the vertical load, axial forces of mainring beams caused by reaction force of outward displaced diagonals is too large to beignored. Axial forces of main ring beams have to be considered for over half storiesupward from the base, particularly for large aspect ratios and polygonal structural planwith less side number. Generally, compared with the traditional structures, twistedstructures with the accumulative rotation angle of90degrees at the top can significantlyimprove the mechanical performance, furthermore, the fewer sidesof the polygonalstructural plan it has, the more remarkable effect it brings about.