EVALUATION OF 2D COUPLED GALLOPING OSCILLATIONS OF SLENDER STRUCTURES

The necessary conditions for the occurrence of 2D coupled galloping os cillations and a description of the set of general differential equati ons for 2D coupled galloping vibrations are established in this paper. A procedure to predict the 2D coupled galloping oscillations is propo sed. Wind loading was treated as a stochastic process including mean a nd fluctuating components caused by atmospheric turbulence. The formul ae and the procedure presented permit a better assessment of galloping oscillations of a prismatic structure which has the same natural freq uencies-in the directions of the two orthogonal horizontal axes. The e ffects of turbulence on 2D coupled galloping are investigated. It is s hown that 2D coupled galloping oscillations mainly occur in the cross- wind direction. The effect of the turbulence integral scale an the ons et wind velocity of 2D coupled galloping oscillations is negligible. H owever, the turbulence integral scale has certain influences on the rm s response both in the along-wind and the cross-wind directions when t he wind velocity is equal or close to the onset wind velocity for gall oping. An increase in the turbulence integral scale in the range of 10 -40 m considered in this paper increases the galloping response. (C) 1 998 Elsevier Science Ltd. All rights reserved.