Effect of recessed cavities on wind-induced loading and dynamic responses of a tall building

This paper investigates how the presence of recessed cavities modifies the wind-induced loading and dynamic responses of a tall building. The H-shaped is selected to represent a building section with two recessed cavities. Nine H-section tall buildings, with a systematic variation of breadths and depths of the recessed cavities are tested in the wind tunnel. All H-sections have the same square envelope and all buildings have a height-to-breadth ratio at 6. Fluctuating wind forces and moments on the buildings are measured with a high-frequency force balance from which wind-induced building responses are estimated. It is found that the most important effect of a recessed cavity is the significant reduction of across-wind excitations and responses of the tall building for normal wind incidence on the building face with a cavity. With an aim to understand the mechanism of this wind load modification, wind pressure on all faces of the H-section tall buildings are measured with a multi-point pressure scanning system from which time histories of wind forces on different building faces are obtained. Correlation analysis of these wind forces suggests that while the magnitudes and phase relationship of the fluctuating across-wind forces coming from the two building side faces are not largely affected by the presence of recessed cavities on the windward and leeward building faces, the contribution to the overall across-wind force from wind pressures on the inner faces of the recessed cavities acts in a slightly opposite action to the main contribution from the building side faces. This explains the reduction of overall across-wind excitation on the building.

► Presence of recessed cavities on a tall building reduces across-wind excitations.
► The reduction occurs for normal wind incidence onto the building face with a recessed cavity.
► In general, greater reductions are found with presence of deeper and wider cavities.