| An aerodynamic model is defined as a wind-tunnel model used to measure the externally applied, or aerodynamic, load due to wind, in a form from which the dynamic response of the prototype can be readily calculated for various values of wind speed, density, stiffness, and damping.;Aerodynamic models have been developed during the past 10 years and are now routinely used, in the form of an aerodynamic base balance, to determine the wind response of tall buildings. The advantages of this method over the traditional aeroelastic model test are so great that informal acceptance has outpaced its technical development. Effects of nonideal model shapes, coupled components, and aeroelastic response have not been satisfactorily resolved.;In its simplest form, the aerodynamic base balance method applies to a structure having mode shapes which are linear in sway and constant in torsion. Real structures do not satisfy this and adjustments are necessary. Adjustments proposed in the literature are incomplete and have resulted in widespread misunderstanding of their significance. An approach for mode-shape adjustments is developed herein which relies on understanding the underlying physical phenomena, separating deterministic from unknown effects to express the real uncertainty involved. The method is further expanded to include mode shapes which are coupled in two or more components.;An aerodynamic base balance was designed, constructed, and placed into routine service. This has required a number of practical difficulties to be overcome, including signal/noise ratios, bandwidth maximization, and complex data reduction.;Validation of the method is demonstrated by comparing the results of aerodynamic and aeroelastic models of an 8:1:1 square cylinder while varying the parameters velocity, density, stiffness, and damping over a wide range. It was found that the degree of aeroelastic amplification can be expressed concisely as a function of reduced velocity and the Scruton number. The amplification is near unity for a wide range of practical values. Further validation and a high degree of accuracy is demonstrated for additional practical structures, including a tall building for which full-scale field measurements were available. |
