The effectiveness of various structural systems in reducing tall building response due to wind

Abstract

Recently, many tall building structural systems have been innovated in order to reduce the building responses due to wind loading. However, there are no systematic study conducted on the effectiveness of the different tall building systems in minimizing the responses of the building due to wind load. The objective of this research is to study the effectiveness of five tall building structural systems: core wall, outrigger, belt wall, tube-in-tube and megacolumns in minimizing the building responses due to wind. Reinforced concrete buildings with 64 stories and the ratio of height to the breadth of 6:1 were analysed for their responses to wind load. The buildings that were analysed have five different structural systems. The natural frequencies and eigenvectors of the buildings in the along-wind, across-wind and torsional mode are computed by a structural engineering software. The along-wind responses are determined by employing the procedures from the ASCE 7-02 while the across-wind and torsional responses of the buildings are calculated based on the procedures and wind tunnel data available in a data base of aerodynamic load. The database is comprised of high-frequency base balance measurements on a host of isolated tall building models. It is found that increasing the size of the core wall is more effective to reduce the building responses than increasing the thickness of the core wall. As for the outriggers, the most optimum position to construct the outriggers is between one quarter to two third of the height of the building. However, outrigger system is effective to reduce only the along-wind and acrosswind responses. The torsional responses cannot be reduced by the addition of the outriggers. Interestingly, the addition of the belt walls will reduce the torsional response of the buildings which otherwise cannot be lessened by the outriggers. The belt walls also further reduce the building responses in the along-wind and acrosswind directions. Moreover, the most optimal tube-in-tube structure is achieved when the spacing of the exterior columns is 4 metre, while the addition of megacolumns to the structural systems reduces the building responses drastically in all the three directions.