Comparative BehaviourOf High Rise Buildings With DiagridsAnd Shear Wall As Lateral Load Resisting System

Abstract

Structural systems for tall buildings have undergone dramatic changes after observing that conventional Rigid Moment Resisting frames alone, the earlier predominant structural system for steel or concrete tall buildings was inefficient in resisting lateral loads. The intensity of the seismic and wind load increases with increase in height of the structure and demand the use of an additional Lateral Load Resisting System (LLRS) for enhancing performance. The LLRS for high rise buildings depend largely on the height of the building. Some of the LLRS that are currently used are Shear Wall (35m), Tube Structures- Frame tube (80m) and bundled tube (100m), Diagrid (100m), Super frames (160m) etc. Diagrid is a technique typically used for constructing large steel buildings by creating external triangular structures with horizontal support rings. The Diagonal members in Diagrid structural systems can carry gravity loads as well as lateral forces. In the present study, the behaviour of Diagrid structures in terms Lateral sway is compared with that of building with shear walls to evaluate the efficiency of Diagrid structures. A 45 storey steel building with a plan area of 36×36m and triangular pattern for diagonal members with a Diagrid angle of 63? is considered. The variations considered are density of Diagrid as 3, 4 and 6 and length of Shear wall, each 6m and 12m along X and Y directions at the corners of the building. Seismic analysis is carried out for seismic Zone V considering various load combination as per IS Codal provisions using SAP2000 V-15.It is found that Lateral displacements of a Diagrid structure are much less than that of shear walled structures proving its efficiency. The study also determines the optimum density of Diagrids considering the structural behaviour and practical considerations.