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# Vierendeel Truss Design3

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## Vierendeel Truss Design

(OP)
I am looking into an existing steel truss design. Its a box type with no diagonals. Does anyone have any tips on its design or references for a Virendeel Type Truss.

### RE: Vierendeel Truss Design

Have a look at this link:
users.pandora.be/karel.roose/vierendeel for pictures of Vierendeel bridges. Take a close look at the information page http://users.pandora.be/karel.roose/vierendeel/waterhoe... it shows the first Vierendeel bridge built by A. Vierendeel himself. If you need translation to english let me know.

### RE: Vierendeel Truss Design

I did a preliminary design for a pedestrian bridge using a vierendeel truss (too expensive).  I used a typical space frame analysis to determine forces and then determined the allowables based upon "non-braced" frame equations (no diagonals).  In other words, it's not really a traditional "truss" because all the joints must transfer moment, shear, and axial forces.  Good Luck.

### RE: Vierendeel Truss Design

I did one similar a few years back.  Hopefully, I did it right! If your top and bottom chord are the same, it's a bit easier.  Unfortunately, mine were not.  You know, for all intensive purposes, the deflection of the top chord is the same as the deflection of the bottom chord.  Therefore, your loads will be distributed rationally.  If the two chords are the same, half the load goes into the top chord and half into the bottom.  If not, it's ratioed by their moment of inertias. For the proportion in the top chord, Itop/(Itop + Ibott.)* the uniform load and, obviously, the bottom chord is taking the remaining load.

I calculated the maximum bending moment and shear in the top chord by placing the total uniform load across it, with vertical point loads acting upward at the uprights.  The vertical point loads are the tributary width between the uprights * the load for which the bottom chord is responsible. I aslo calculated the maximum bending moment and shear in the bottom chord by placing the vertical point loads down on it.  Check both chords for shear capacity.  If the point loads are high, which they probably will be, you'll need to check for crippling of the webs of the chords.

I then calculated what the total moment of the truss would be which, for me, was just (Uniform load * Length^2)/8.  Then I took this number and divided by the distance between the neutral axis of the top and bottom chord to get my axial force in the members (F=M/D).  Once you have the axial forces check the top and bottom chord for combined axial and flexure.

Check the verticals for axial capacity.

FYI the top chord of the one I analyzed was overstressed by about 5%, so I just added additional bracing.

Hope this helps,
Chip

### RE: Vierendeel Truss Design

Just fabricated a Vierendeel style truss, pedestrian bridge, from HSS ASTM A500 Steel.   All welded joints were full penetration with backing.

I estimate this style of truss with full pen welds cost $15000 more than a comparable warren truss fabricated from HSS. After a special UT procedure was developed and qualified, all welded joints were 100% Ultrasonic inspected. UT acceptance was over 90% so rework was nominal. The Vieredeel Truss looks nice but at a co$t.

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