Aerodynamic stability of a truss-stiffened cable-stayed bridge

Abstract

Wind tunnel tests have been conducted to evaluate the aerodynamic stability of a proposed design for a truss-stiffened cable-stayed bridge. The tests were performed in an open-circuit laminar flow wind tunnel using a 1:60 scale section model representing a 300-ft (91.46-m) segment of the main span. Wind speeds up to and beyond the design speed of 150 mph (240km/h) were simulated as were wind angles ranging from −4 to +6 degrees. Under these conditions, the bridge section exhibited little or no tendency toward vertical motion. The bridge model does, however, demonstrate a sensitivity to vortex-induced torsional vibrations over the full range of wind angle. In addition, the section model ultimately becomes unstable due to single degree-of-freedom flutter in torsion.