Wind Actions on Cable-Supported Bridges

This paper addresses the wind actions on cable-supported bridges including the relevance of wind tunnel testing. Background is given on flutter and vortex-induced vibrations, from which wind tunnel testing is made necessary. References will include wind actions on long span bridges in the United States, Canada, Norway, and Denmark. A long term experience have shown that section model wind tunnel tests may be efficient and accurate when predicting wind-induced vibrations on bridges. The combination of full-scale measurements and experimental wind tunnel data complement each other giving the most accurate wind-induced response of the structure. For very streamlined bridges often used for European cable-supported bridges, vortex-induced vibrations measured in the dynamic test rig may depend on the Reynolds number and hence the length scale of the section model. Experimental data is taken from 1:10 and 1:50 section model tests performed in large and small boundary layer wind tunnel facilities with an h x w cross section of 3.0 x 2.5 m and 1.55 x 1.75 m, respectively. Low Reynolds numbers simulated with a 1:50 scale model give much larger vibrations than found for intermediate Reynolds numbers simulated with a 1:10 scale model. This behavior is similar to the behavior of circular cylinders. Full-scale measurements performed on Great Belt Bridge show a good correlation with wind tunnel tests on scale 1:50 section models.