Measurement of forces and base overturning moments on the CAARC tall building model in a simulated atmospheric boundary layer

Mean values, rms values, and the spectra of forces and base overturning moments have been measured on a CAARC building model in a nominally uniform flow and in a simulated atmospheric boundary layer. The measurements were made at wind angles, α, in the range from 0° to 90°, α = 0° being when the flow is normal to the wide face of the model. The purpose of the work was to acquire data which may be useful for design and to use the data to describe some of the features of the flow. For a given undisturbed steady streamwise velocity at roof top, rms values of forces and moments measured in the simulated atmospheric boundary layer can be more than four times the uniform flow values. If the wind is normal to the wide face of the model and a change is made from the uniform flow to the simulated boundary layer, then C D (the drag coefficient based on the average value of the dynamic head) increases, organised vortex shedding persists, and the tendency to gallop remains strong. By contrast if the wind is normal to the narrow face of the model, then C D is virtually unchanged, the shedding becomes disorganised, and the tendency to gallop is suppressed. In both the uniform flow and in the simulated boundary layer, high local base suction associated with organised vortex shedding may occur near the bottom of the model.