AN INVESTIGATION OF WIND INSTABILITY OF LONG-SPAN BRIDGES BASED ON THE CONCEPT OF AEROELASTIC MODES

Because of their advantages - ease of testing, good control of simulated conditions, etc. - wind tunnel tests using spring-suspended sectional models are generally employed in the examination of aerodynamic instability of long-span bridges. As the spring-suspended sectional model is two-dimensional and rigid, several questions remain in order to accurately estimate aerodynamic instability of bridges based on tests of sectional models. This is because the full bridge is a three-dimensional structure affected by aerodynamic forces - wind velocity, angle of attack, amplitude, sectional shape of bridge decks, etc. - and these forces generally vary across the span. This paper discusses investigation of wind-induced instability of full bridges from sectional model tests, using the concept of aeroelastic modes. It is intended to clarify the significance of sectional model tests in the wind resistant design of bridges, especially with reference to the relation between two-dimensional models and three-dimensional structures.