Wind loads for high-rise buildings constructed in Sri Lanka

Abstract

In the design of high-rise buildings, it is of paramount importance to control the wind induced accelerations of the buildings to acceptable limits so that the majority of occupants will not feel the wind induced movements of the building. In this respect, it is necessary for the structural designer to evaluate the dynamic behaviour of the building at a very early stage of the design, on the basis of appropriate wind velocities. It is shown here that the 3 second gust wind velocities used for zone 3 of Sri Lanka could be too low for high-rise buildings. The use of low velocities may not control the drift index sufficiently so that the designers may come up with flexible structural forms that would have a dynamic behaviour unacceptable to the occupants. In order to control the drift index adequately, it is suggested adopting an average basic design velocity of 30 m/s for the high-rise buildings constructed in zone 3 and 2 of Sri Lanka. It is also shown that when higher design velocities are used, it would be appropriate to use gust factor method which takes account of the dynamic behaviour of the building for the evaluation of wind loads for structural design purposes.