vierendeel truss analysis 3

[joistg]

I have to analyze warren truss with one diagonal missing somewhere in the centre of the truss.I understand that top and bottom chords will have additional moments. The required opening in the truss should quite large, so there is no room for reinforcing both top and bottom chord of the truss. Also, it is a matter of saving (there is lots of trusses like this). How can I analyze this truss? Also, should I be concerned about deflection and how can I calculate it?

 

[joistg]

paddingtongreen,

I do not understand this:
"two, four bay trusses, connected by a beam, bridging the central gap, the beam connected to the first two node points on either side of the gap". Can you explain?

 

[BAretired]

One four bay (or panel) truss to the left of the opening, the other to the right. The beam bridging the central gap consists of four angles which attach to two node points of each truss.

By anti-symmetry, the beam has an inflection point at the middle of the opening, so you are dealing with two propped cantilevers with a load applied at the inflection point. If you want to consider the bottom chord contribution, you have another pair of propped cantilevers of different stiffness.

BA

 

[BAretired]

You really should include the bottom chord in your analysis as it has a shorter backspan than the top chord.

BA

 

[rb1957]

"all i said was that this halibet was good enough for Jehovah"

 

[dhengr]

Yah, yah..., halibut, shmalibut..., Jehovah only had an 2-bit abacus and all the beads were the same color.

 

[ToadJones]

If you cannot use an abacus for your calcs, you are not a real engineer.

 

[csd72]

If you need an abacus for your calcs then you are not a real engineer!

 

[dik]

ToadJones... I was thinking of producing a workable solution... I hope that you're not of the opinion that a FEM model will provide more accuracy <BG>... at best, it just gives you numbers... as noted earlier, if you have a bunch of these, it would warrant doing a refined analysis...

Regarding an abacus... I worked with a Chinese engineer about 40 years back that used an abacus... really a fast calculator if you know how to use it...

Dik

 

[rb1957]

certainly FE gives you a bunch of numbers (and some very nice pictures), but i would say it does improve the accuracy of the answer (else why do it ? maybe 'cause you can't do a hand calc ??) ... a hand calc would require a bunch of assumptions to simplify the real problem to something solvable, and most of these are explicit (ie clear to the analyst and the reviewer) but some are implicit (ie hidden). a problem with FE is that there are alot of implicit assumptions, and it's thse guys that'll get you in trouble.

 

[ToadJones]

dik-
take my post with a grain of salt...I wasn't seriously issuing a challenge.
FEM would produce, instantly, more numbers.
Several of these would be very accurate deflection numbers. Deflections that might control the design. Ponding comes to mind.