| The prediction of the response of a long-span bridge structures to wind excitation is a complex task. The nature of the forces involved requires simultaneous analysis of the dynamic properties of the structure and careful evaluation of the aerodynamic loading acting along the bridge span. Assessment of aerodynamic loads for any specific structure is usually not possible without experimental testing in wind tunnel.;This study discusses results and challenges associated with the design, assembly and calibration of a wind tunnel balance for the measurements of aerodynamic loads from section model dynamic experiments, and representing at a reduced scale the behavior of the typical cross section of the bridge. This balance was recently conceived and developed at Northeastern University. The force balance, employed for the testing, was installed in an existing wind tunnel with a relatively small test chamber.;Using a combination of wind-tunnel experiments, analytical modeling and system identification techniques, the dynamic response of a two-degree-of-freedom system, simulating the motion of the actual deck under steady wind excitation, was carefully determined. Investigations were based on a frequency-domain method for the extraction of motion-induced coefficients (flutter derivatives). This formulation directly takes into account fluid-structure interaction coupling effects as part of the simulation of the dynamic response of a long-span bridge to wind excitation. The section model corresponding to the prototype deck of the Carquinez Strait Bridge, a suspension bridge located in San Francisco Bay (California, USA), was used as a benchmark case for validation of the experimental setup. Despite the inherent scale limitations of this facility for research applications, good correspondence was observed between the measured quantities and their reference values, derived from the literature. |
