Reduction in Shear Lag Effects in Tall Buildings Using Exterior Bracing and Diagrid Systems (Recent Developments-review paper)

Abstract

The structural and architectural aspects of the exterior bracing and diagrid systems - two systems which generally reduce building materials, enhance structural performance, and decrease overall construction cost achieve sustainability. When a structure is completed it is expected to look elegant, appealing and, above all it must be structurally correct. These structural systems, diagrids and exterior bracings can visually communicate the inherent structural logic of a building while giving artistic effect. This creates the structural elements that are aesthetically pleasing and geometrically coherent, while also respecting the laws of mechanics. The diagrid (diagonal grid) structural system has now become increasingly popular. A diagrid system consists of series of triangles and horizontal rings of beams which provide the structure support against gravity and lateral forces, while also making a building stiffer and often lighter than a traditional high-rise. Diagrids are usually composed of steel, because of its high strength and ability to resist both tensile and compressive forces. The diagrid can suffer from problems of implementation due to its complicated steel joints, but recent advances in joint detailing and prefabrication are helping to address this issue. Due to their triangular configuration, diagrids can efficiently carry the shear and moment caused by lateral loads and gravity. They are effective in minimizing shear deformation, providing maximum resistance against torsion. In this paper, shear lag effect is being studied based on various works reported and is correlated with stiffness of the building. The study is also done for the different patterns of bracing systems the blend of structural performance and aesthetics, examined to facilitate a better understanding of the aesthetic developments in skyscrapers around the world. For this purpose, different geometric patterns of bracing system are considered. For a relative study for shear lag effect, cross-sectional dimensions of beam and columns, their alignments (column) and the material properties are assumed to be same throughout the height of the building. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads.