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.
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