Improvement of occupant comfort of tall buildings with outriggers

Abstract

The national tend in Sri Lanka today is to construct tall buildings in city centers. This may be due to various reasons such as availability of only a limited space in commercial areas and city centers, convenience in operational activities, aesthetic aspect and elegance. The developments in concrete technology make the latest building much more taller and lighter than the earlier buildings. In the design of tall buildings, it is more important to control the wind-induced acceleration to acceptable limits so that the majority of occupants will not feel the wind induced movements of the building. It is necessary for the structural designer to evaluate the dynamic berhaviour of the building at the early stage of the design on the basis of the appropriate wind speeds. This means that the design engineer has to optimize the lateral load resisting system by adopting efficient structural arrangements. Install flexible buildings, it is important to control the drift of the structure as well which is generally expressed as a drift index. If excessive drift occurs, occupants may find it disturbing and some partitions and finishes may be damaged. Excessive drift can be controlled by changing the geometric configuration of the structure, increasing the bending stiffness of horizontal members and adding additional stiffness using core members, coupling the shear walls and providing the outriggers. This study was carried out to determine the optimum use of outriggers for controlling the wind-induced behaviour on tall buildings. A detailed case study was carried out for thirty and fourty storey buildings for various loading conditions by providing outriggers at different levels. The results indicated that the ideal location for outriggers is just below the level where the hard zoning arrangement necessitated the termination of some parts of the lift core. The results of this study can be used as guidance for controlling deflection and acceleration due to wind effect in tall buildings. II