On Wednesday 08 August 2007 23:09, R.C.Macaulay wrote: > Not a pretty picture. One note, officials have denied that the > > resurfacing of the bridge had anything to do with the failure; so, you > > know what *that* probably means. > Terry wrote, > Nope, it had absolutely nothing to do with the fact that the bridge > was being resurfaced: > > > Howdy Terry, > > I looked at the inspection reports you posted. At best the truss materials > were an "erector set". Surprised me the bridge was a 1960 model.. I thought > it was a 1938. dont know where I got that idea. The structural engineer that > has his name on this problem will live with it. > > Richard > >
The truss IS and 'erector set'. I am sure that you had one as a boy as well as I did. It was fun, and we learned what would work and what would not. As for the controversy over the 'gusset plates', readers should know that this is not a standard one size fits all part. Every joint of a truss like this had to be stress analyzed for proper resistance and designed accordingly. This means not only thickness, but shape (dat other dimension) as it will have to follow the connected members. Also the bolt pattern, number of bolts, and size of bolts, centroid of action of this bolt pattern, the relationship of this centroid and the resistance of the pattern with the respect to the applied forces. In addition, some or all of these joints may be considered not only pinned connections like in a classical truss, but also framed connections where resistance to torsional loads (rotation about a joint in three dimensional space) must be considered. In a truss frame of many members like a bridge, a computer will be required to do all the load balancing and slope deflection analyses. Now if the computer was not programmed right, then 'garbage in, garbage out'. One cannot dismiss these gusset plates as simply designed and uniform members of the structure. They are in fact the hardest to analyse and design. Standing Bear
