Experimental investigation of blockage effects on fluctuating wind forces on standard tall building models

In order to investigate the blockage effects on the fluctuating wind force coefficients and the base moment coefficients acting on standard tall building models, a series of standard tall building rigid models with different blockage ratios (1.7%, 3.1%, 4.5%, 6.3%, 8.6% and 10.1%) were tested by measurements of synchronous multi-pressure sensing system (SMPSS) in smooth and grid turbulent flows, respectively. The results show that the blockage effects on the fluctuating wind force coefficients of each layer and the corresponding base moment coefficients are very small in the smooth flow when the blockage ratio is less than 4.5%. With the increase of the blockage ratio, the fluctuating wind force coefficients of each layer and the corresponding base moment coefficients increase, in particular for the across-wind forces, when the blockage ratio is larger than 4.5%. In the grid turbulent flow, the fluctuating wind force coefficients and base moment coefficients on the tall building are larger than those in the smooth flow. Moreover, the increasing turbulence suppresses the blockage effects on fluctuating drag coefficients and the corresponding along-wind base moment coefficients, and weakens the blockage effects on fluctuating lift, torque coefficients and their corresponding base moment coefficients to some extent. Based on the test results, the modified formulas for the blockage effects on the fluctuating wind forces on standard tall buildings are proposed. The outcomes of this paper can be a useful reference for relevant research. © 2019, Editorial Office of Journal of Building Structures. All right reserved.