Measuring Flutter Derivatives for Bridge Sectional Models in Water Channel

Abstract

Experimental results of flutter derivatives for sectional models of long-span bridges are presented. The tests were carried out in the Water Channel Laboratory of the Center for Applied Stochastics Research of Florida Atlantic University, which has an 8-m-long test section and a maximum flow speed of 0.5 m/s. The experiments were conducted in the forced-oscillation mode. Specifically, each model is forced to execute a sinusoidal motion, either torsional or vertical, one at a time. In each test, both lift force and torsional moment are measured to obtain the noncoupled flutter derivatives as well as the coupled ones. The advantages of using water as the fluid medium, instead of air, are described. The flutter derivatives obtained in the water-channel tests are then compared with some published data obtained in the wind-tunnel tests using the free-vibration mode. The comparison shows that the water-channel data and the respective wind-tunnel data share the same trends. Finally, the measured flutter derivatives are converted to the corresponding impulse response functions required for the stochastic stability analysis in the time domain.