Ladder column

[LOKSTR]

I have a vertical wind column which is in the form of a ladder with outside and inside chords 300mm apart and rungs @ 300c/c. The column is oriented such that the wind is parallel to chords(side of ladder). The tributary wind area is 8'x40' (wxh). The outside chord is pinned at top and bottom.

All the members are welded and are of 4"x4"x0.095" thick.

Can it be taken as a truss or not? Since there are no diagonal web members and it is not acting as Viendeel truss also.
I need to calculate section modulas Sxx (in the plane of chords)for the ladder column.

Any help/guidance will be greatly appreciated.

 

[civilperson]

It is exactly a Vierendeel Truss, no diagonals and thus bending moments are transferred to the chords/webs. The connections,(welded), are capable of transferring moments.

 

[LOKSTR]

Civilperson,

The web member itself is not capable of taking the moment at the junction of chord and web. I have around 15kn-m of moment at this junction if I treat it as a vierendeel truss. All members are only 12gauge thick.

 

[hokie66]

Your wind column has no chance of spanning 40'. Back to the drawing board. These members are much too light.

 

[COEngineeer]

you can call it vierendeel truss if you analyze the welding of the each ladder plate instead calling it pin. Or you can analyze it as double plate (outside+inside chord) taking the load and forget about the web. If that is good, then call it good.

Never, but never question engineer's judgement

 

[civilperson]

By definition: A Vierendeel Truss has no diagonals and must transfer moments through the connections. How else do you propose to transfer the forces if not through the connections, (no diagonals remember). A possible cure is to plate the rectangles made up of overstressed members.