Aerodynamic Investigations of the Luling, Louisiana Cable-Stayed Bridge: Fid-Bau Portal

Aerodynamic Investigations of the Luling, Louisiana Cable-Stayed Bridge

H. R. Bosch

This report presents results of a comprehensive laboratory test program recently completed by the Federal Highway Administration, Office of Research. Wind tunnel tests on section models of the proposed cable-stayed bridge across the Mississippi River at Luling, Louisiana were conducted to determine the aerodynamic stability of the suspended span and main towers. Seven different deck configurations were tested, and their critical flutter wind velocities and the vertical motion caused by vortex shedding determined. Based on overall performance, one of the seven models was chosen as the preferred configuration. Three erection stages of the preferred section and one tower erection stage were then tested and their drag coefficients, including that of the preferred section, determined. Flow fields surrounding the deck and tower were investigated for the purpose of developing field wind instrumentation. The following conclusions are presented: (1) the prototype bridge should not experience aerodynamic instability due to flutter; (2) assuming 1% structural damping, vortex induced oscillations should not be a threat to bridge safety or cause for discomfort to users; (3) drag forces measured are reasonable relative to AASHTO design values; (4) none of the erection stages of the bridge deck and tower tested exhibited instability tendencies; and (5) mounting wind monitors on top of lighting poles 35 to 40 feet above the center barrier appears necessary to avoid the boundary layer effect.