NHL Forces on a Truss

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Chris Achilles
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Location: BOLTON

NHL Forces on a Truss

Post by Chris Achilles »

I've got a heavily load trussed box structure (22m x 6m x 5m high) with most of the loads applied to beams supported by the bottom booms and I'm a bit puzzled about where to apply the NHL forces. The end diagonals go to the top of the end posts so most of the force is applied to the ends at high level. The end frames are moment resisting and susceptable to sway. If I apply the floor NHL forces at low level then the structure walks it as none sway (braced below bottom boom). If I apply the proportion of NHL forces calculated from the load in the end posts at high level (where they actually apply) then it becomes a sway frame. I think I'm going to apply most of the NHL force at high level to the end frames and add some stiffness to make it none sway (Just out - Lambda Crit 9). Anyone come across this problem? - Am I being too conservative? Loads applied at bottom boom level but ultimately supported at the top boom level?

Any opinions would be appreciated.
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