Physics-Based Method for the Removal of Spurious Resonant Frequencies in High-Frequency Force Balance Tests

Abstract

The high-frequency force balance (HFFB) test is a widely used method for estimating lateral turbulent wind loads on tall buildings in a wind tunnel. The method relies on use of a highly accurate force sensor placed at the base of the tall building model to measure base forces and overturning moments. Because the turbulent wind load excitation is broadband, it is important to adequately design the connection detail between the model and the sensor. Accurate design is needed to avoid contaminating the measurement of the lateral wind loads by the potential spurious resonant effect, which is induced by flexibility in the connection detail. This design often relies on the experience of the wind tunnel modeler. On occasion, because of the limitations of test setup and environment, the connection detail between the building model and the HFFB force sensor may not be sufficiently stiff. Consequently, resonant response caused by the flexible connection may affect the power spectral density function of the measured wind loads. One of the methods to address this problem is to filter the HFFB output signal and to remove undesirable response within a specific frequency interval by conventional digital filter methods. However, this may cause the removal of important features of the wind loading. This paper presents a simple yet efficient method, based on classical dynamic theory, to eliminate the spurious effect. The method is applied to the “correction” of an experimental wind load spectrum.