Abstract
Outrigger is one of the tall building structural systems that are used to reduce the building responses due to the wind. Outrigger is a stiff beam that connects the core wall to exterior columns and this enables the vertical shear to be transferred from the core to the external columns, thereby forcing the perimeter columns to participate in carrying the overturning moment due to the wind. Belt wall is often added to a building with outrigger system to further reduce the displacement and acceleration of a tall building having an outrigger system. However, it is not known how effective the belt wall is in further reducing the building responses. Thus, 64 story reinforced concrete buildings are studied in order to determine how the belt wall improves the building responses due to the wind. Buildings with an outrigger system and buildings with a combination of the outrigger and belt wall system are analysed by a structural engineering software in order to determine the natural frequencies and eigenvectors in the along-wind, across-wind and torsional direction. The along-wind responses are determined by employing the procedures from the ASCE 7-16 while the across-wind responses of the buildings are calculated based on the procedures and wind tunnel data available in a database of aerodynamic load. Results from the analysis show that the belt wall reduces the along-wind and across-wind responses slightly. However, belt wall reduces the torsional acceleration of the buildings significantly, which otherwise cannot be reduced by the outrigger system.
Highlights
Deflection and acceleration of tall buildings must be controlled as large deflection and high acceleration may cause discomfort to the building occupants
The reduction of the across-wind responses due to the wind in all the three wind environment: Malaysia, New York and Hong Kong when belt walls are added to the buildings with the outrigger system is less than the reduction of the acrosswind responses when the outrigger system is added to a building which has no outrigger at all
The purpose of conducting the study on the belt wall system is to find out how the addition of the belt walls improves the responses of a building which already built with the outrigger system
Summary
Deflection and acceleration of tall buildings must be controlled as large deflection and high acceleration may cause discomfort to the building occupants. Deflection of more than 1/200 of the height of the buildings, for example, can result in improper drainage, impaired operation of doors and windows, and damage to lightweight partition [1]. The deflection cannot exceed a certain limit that has been specified by the local building authorities. The limit of drift index, which is the ratio of the maximum deflection at the top of the building to the total height is between 0.001 to 0.005 for different countries. The maximum total drift and interstory drift of structure that is subjected to wind force allowed by Malaysian Code, MS 1553:2002 [2], is 1/500 and 1/750 of the height, respectively. [3] recommended the drift limits of building to be between 1/600 to 1/400
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