A new method for dynamic parameters identification of a model-balance system in high-frequency force-balance wind tunnel tests

The high-frequency force-balance (HFFB) technique is one of the most popular methods for assessment of the wind-induced response of tall buildings. Before the measured data being processed, an additional treatment should be made to modify the amplification caused by the model-balance system. This procedure requires determining the dynamic parameter of the model-balance system first. The knocking test method is usually adopted to identify the natural frequency and damping ratio of the model-balance system. However, there are some shortcomings of this approach. First, it requires an additional knocking test, and second, the identified damping ratio by adopting the knocking method is only the structural damping of the model-balance system and the aerodynamic damping of the model is neglected. In this study, a new approach is proposed to identify the natural frequency and damping ratio of the model-balance system based on the measured data in wind tunnel tests. The knocking test is no longer necessary and the identified damping ratio is the entire damping ratio of the model-balance system, that is, the structural damping and the aerodynamic damping are both included. Three illustrative examples, including a hypothetical building, the Commonwealth Advisory Aeronautical Research Council (CAARC) tall building, and two actual buildings with rectangular and nonrectangular cross-sections, are considered to examine the validation of the proposed method. It is shown that the damping ratio of the model-balance system is different under different wind directions, and the actual power spectral density (PSD) of the overturning moments at the base of the model can be calculated accurately by adopting these identification results.