huangyhg

help with old steel roof truss
i am trying to find a reference for the design of a steel truss with the type of connection shown in the attached picture. thanks for the help.
this looks like a gable truss with a knee brace. both connections to the column look like they may be pinned (which is normal). knee brace is for lateral stability. i suggest you model this on the computer rather than by hand.
it looks like a wind brace added to a truss to provide stability. it's very common. look for a steel design book with examples of industrial buildings. i have one called "design of structural steel" by lothers which i suspect is out of print.
those should be picking up some lateral and inducing moment into the columns.
it looks like a modified "fink" truss with knee brace. at the time of (old) design, all connections were considered pinned, and the truss was simply supported. this type of truss can be found in many old industry buildings with span up to 120', the knee brace reduces the span length, and brings the thrust to a point lower than the end bearing, thus stabilize the truss and reduces the tendency of sagging (deflection).
a predecessor to a tapered beam, rigid frame bent...achieves same result. chances are this truss is much better built than most anything you'll find today! lateral x brace and tie rods....what is the span on this truss?
it would be interesting to model this, but keep in mind it was designed by hand with a slide rule, so if you try to "over think" the connections, it might not be a representative model!

ron:
full agree with you. this type of roof truss is of rare use in modern buildings, however, it has stood with time and been proven for sheltering industrial buildings. ironically, with the rapid advancement in computer technology, the over-thoughts may have just killed the simplicity of the good-old design.
thanks for all of the input. the span is 40'.
you can see a section of the building in my other post titled warhouse renovation.
thanks again.

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