Single load path structures, although not preferable for bridges, are "almost indispensable" in many circumstances (CSA, 2006b). Therefore it is important to understand the behaviour, especially the post-yield capacity, of such structures to derive proper design and evaluation approaches. An investigation of the load paths in conventional steel through-truss bridges has been carried out for the Grand River Bridge at Cayuga, Ontario. Three load paths not conventionally assumed in design and evaluation are identified with their associated necessary conditions, critical members and unintended consequences. To "expose" the hidden load paths, the conventional load paths are first disabled by removing one of the main truss members and the subsequent behaviour is analyzed using ANSYS. An example of an unconventional load path attributable to the torsional stiffness of the through truss bridge is discussed in detail. When an end post is removed, the torsional stiffness of the bridge prevents failure of a typical through-truss span essentially under dead load only.
展开▼
