Extraction of bridge aeroelastic parameters by one reference-based stochastic subspace technique

Abstract

Without output covariance estimation, one reference-based Stochastic Subspace Technique (SST) for extracting modal parameters and flutter derivatives of bridge deck is developed and programmed. Compared with the covariance-driven SST and the oscillation signals incurred by oncoming or signature turbulence that adopted by previous investigators, the newly-presented identification scheme is less time-consuming in computation and a more desired accuracy should be contributed to high-quality free oscillated signals excited by specific initial displacement. The reliability and identification precision of this technique are confirmed by a numerical example. For the 3-DOF sectional models of Sutong Bridge deck (streamlined) and Suramadu Bridge deck (bluff) in wind tunnel tests, with different wind velocities, the lateral bending, vertical bending, torsional frequencies and damping ratios as well as 18 flutter derivatives are extracted by using SST. The flutter derivatives of two kinds of typical decks are compared with the pseudo-steady theoretical values, and the performance of <TEX>$H_1{^*}$</TEX>, <TEX>$H_3{^*}$</TEX>, <TEX>$A_1{^*}$</TEX>, <TEX>$A_3{^*}$</TEX> is very stable and well-matched with each other, respectively. The lateral direct flutter derivatives <TEX>$P_5{^*}$</TEX>, <TEX>$P_6{^*}$</TEX> are comparatively more accurate than other relevant lateral components. Experimental procedure seems to be more critical than identification technique for refining the estimation precision.