Full scale and model studies of wind loads on a pair of circular cylinders

The paper describes a full scale investigation of the wind effects on a group of reinforced concrete chimneys conducted by the University of Western Ontario. Excessive across wind motions resulted in a failure in one of the stacks. The winds associated with the failure were in a direction that was inline with an upstream chimney that was roughly 25% larger in diameter with a spacing ratio of 5.1 diameters. Results suggested that the lift forces due to vortex shedding were amplified by a factor of 3.7 due to buffeting from the upstream structure. Subsequent to the full scale study, model tests were performed in the 1 MW wind tunnel at Monash University to further investigate the effect of buffeting. The maximum Reynolds number achieved was 106 compared to the full scale Reynolds of order 107. The experimental results confirmed, at least in a qualitative sense, that the shedding and buffeting peaks merge causing an increase in the total lift force.