ABSTRACT
Long-span bridge girders are susceptible to torsional flutter. It is generally recognized now that the dramatic collapse of the Tacoma Narrows Bridge was due to torsional flutter. The weak torsional rigidity and aerodynamically unstable cross-section of the girder are two main factors responsible for the collapse. Since theTacoma Narrows Bridge incident, flutter instability had become the most important issue in the design of long-span bridges. To avoid this instability two different design approaches have been proposed; one is by streamlining the girder using box section; and another one is using the truss-stiffened girder.
