Trunnion support plate bending strength

[vi_shj]

Dears,

I have a 8" sch 120 pipe as trucnnion for a frame with 200 mm length. the trunnion in connected to frame by welding a 25 mm thk plate ( 600mm length x 300 mm width ). How to check bending strength of the plate & trunnion pipe. is there any formula in AISC to check the same. Alos one side in CJP weld. which formula in AISC should be used for the same.

Regards
VKM

 

[Tmoose]

Please post twenty seven eight-by-ten color glossy photographs with circles and arrows and a paragraph on the back of each one explaining what each one was to be used as evidence.

 

[vi_shj]

Dear.

Please find the details as attached

 

[dhengr]

Vkmummer:
Is this frame/skid built already or just in the design phase? I think that trunnion detail could be significantly improved, and improve the frame/skid in the process. The long frame members are 24WF beams of what size, and the trunnions will put substantial torsional loadings on these beams unless you install a large enough cross frame beam member btwn. the two 24WF long beams to take the trunnion moments out. These cross frame members should be centered behind/on the trunnions. Then, the 600x300x25 connector pl. should be changed as follows: cut a circle out of the center of this pl. so the trunnion pipe can pass through to the WF web; cut the 600mm down so this connector pl. will fit within the flanges of the WF beam vertically; change the #57 stiff. pls. in height, because they will now sit atop or below the 8" trunnion or on the cross frame beam member; remove the little #59 type stiff. pls., they just mostly add some nasty load/stress concentrations, and shorten the 8" trunnion by 75 or 100mm, to reduce the trunnion cantilever moment. Now, everything from the 24WF web outward can be made-up as a subassembly before it is finally fit/applied to the 24WF beam, and essentially the same subassembly can be done for the cross frame beam and its end stiff. pls. (#57's). You will have some difficult interior welds from the trunnion subassembly to the 24WF web and flgs., so pay attention to welding access. The outer weld to the flg. tips is now just a fillet which is about 1/16th inch smaller than the flg.thk. Your design effort should be to minimize the trunnion canti. moment, then handle it in the most efficient way possible, not by connector plate bending, and get those loads into the web of the 24WF.

 

[vi_shj]

dhengr,

It is in fit up stage. it W24x55 beam with cross beams and stiffeners. client advised to provide 3 stiffener plates at front & back of W beam. But as you told this arrangement makes hard for welding. will this arrangement increase the stress in trunnion and fail?. Please advise. refer attached drawing for more information. expected load is 20 Ton and size is 8" sch 120 A 106G r.B
Thanks in advance

 

[dhengr]

Vkmummer:
The best way to attach your sketches is in PDF format, that works better for us on this end, in terms of viewing, printing for our study and redlining, etc. Using your last sketch, I suggest you reread my earlier post a few more times, sentence by sentence, and redo your sketch according to each step of my suggestions. You do have some nasty stress concentration areas in your detail. You do not have a very clean load path and stress flow situation, and it seems you could reduce the trunnion cantilever length. You do not show the cross beam behind the 8" round trunnion and this is an integral part of a good clean trunnion design. New, improved detail thought...., Ideally, I would just run the 8" round pipe right through the 24WF webs, to make it continuous from trunnion to trunnion. Do you really need 8" Sch. 120 pipe for this? Then, put some kind of doubler pls. (doughnuts, thick washers, .5-.75" thk., o.d. = 12-16" and i.d. to match your 8" pipe) right onto the 24WF webs. You transmit the loads and shears right into the WF webs, where you want it, in a fairly uniform fashion, and the canti. moments and torsional action transfers right through the WF. Trying to transmit the trunnion canti. moment through plate bending (that 25mm connector pl. which is 300x600 in size) and then a complex bunch of stiffeners leads to a bunch of stress concentration locations which are difficult to resolve and rationalize. By eliminating the outside #59 and “D13 “ stiffeners you can reduce the trunnion canti. length by at least 75mm. I have not looked at the exact size and thicknesses, etc. of the various parts, but they look about right proportionally, subject to a cleaned up sketch of the detail and a complete stress analysis of the detail. Doing the above is a slight improvement on my first post, and it will cost you a bit more for the added length of 8" pipe, but when you consider all the junky pieces and fabrication you could save, it would probably be a practical trade off.

Every place you have a stiff. pl. transmitting a load through the thickness of a beam web, and then to another stiff. pl. which crosses the first stiff. pl. is an absolutely awful load path and stress concentration condition which almost defies analysis. When you try to take the trunnion pipe end moment out to the beam through a fairly flexible connector pl., you are sorta designing a pinned connection, or at best a semi-ridged connection, as a function of the pl. stiffness, which is quite low. I would stop the frame fit-up and give some thought to cleaning up the detail and design. This will probably save you some time and headaches in the long run.