Tension Chord Bracing (Built-Up Steel Truss)
Tension Chord Bracing (Built-Up Steel Truss)
(OP)
Hi all
I am engineering a welcome center and in the entrance room, there is a high curved roof that is being supported by built-up steel trusses that span 68 feet long and are generally 30 feet apart.
I was wondering if there are any provisions on tension chord bracing for these long steel trusses? Any help would be greatly appreciated.
Thank you.
I am engineering a welcome center and in the entrance room, there is a high curved roof that is being supported by built-up steel trusses that span 68 feet long and are generally 30 feet apart.
I was wondering if there are any provisions on tension chord bracing for these long steel trusses? Any help would be greatly appreciated.
Thank you.
Struct Engineer






RE: Tension Chord Bracing (Built-Up Steel Truss)
I personally believe that tension chord bracing is a good idea and always use it (if calcs show it necessary). If you think about it, the only thing bracing the diagonals that are in compression are the top and bottom chords. The top chord is usually sufficiently braced, but the bottom chord also needs to provide adequate strength/stiffness to act as a brace for those diagonal compression members.
RE: Tension Chord Bracing (Built-Up Steel Truss)
Section D1 of the AISC does state that an "L/r preferably should not exceed 300" for tension members. This could be achieved by increasing the member size or some form of bracing... but as stated, it's preferred but not required.
Most of the trusses I have designed are for roofs and therefore required some amount of uplift.
RE: Tension Chord Bracing (Built-Up Steel Truss)
There is a very informative AISC engg. Journal by James S. Fisher ( 1983-Q3) on tension chord bracing. You can buy it or if you are a member you can download it free.
Lokstr
RE: Tension Chord Bracing (Built-Up Steel Truss)
I see an awful lot of stadium trusses etc. with no tension flange bracing...
RE: Tension Chord Bracing (Built-Up Steel Truss)
RE: Tension Chord Bracing (Built-Up Steel Truss)
RE: Tension Chord Bracing (Built-Up Steel Truss)
While I may agree that the buckling length of an individual web member would be the actual length (k=1), that still doesn't address the idea of global stability (i.e. LTB of the section).
I'm thinking of sidesway web buckling in a steel beam. I have this paper (I'm attaching it) that talks about how sidesway web buckling manifests itself and how a compressive stress field in the web acts as a column and is dependent upon the tension flange to brace it out-of-plane.
I'm failing to see the difference between this and bracing the tension flange of a truss.