The application of wind-tunnel testing of long-span bridges to their construction

With modern bridges spanning unprecedented lengths, wind-tunnel tests of these light, flexible structures in a boundary layer wind tunnel have become a necessary part of the bridge design process. The focus of the wind tunnel tests varies greatly depending on whether the impetus comes from the owner, designer or contractor. In the case of the Normandy Bridge (Pont de Normandie), the impetus came from the steel contractor and concerned the effect of wind loads during the critical construction phase, when extraordinary 420 m bridge decks will be cantile-vered from each of the two pylons just before closure. This paper presents: i) the particular problems of the bridge during construction; ii) typical wind tunnel tests conducted to measure the critical responses of the bridge; iii) results selected to demonstrate the influence of a mitigation device on the bridge responses and the effect of winds approaching from oblique angles to the bridge axis; and iv) the influence of the test results on the construction of the prototype bridge.