Bolted connection for a beam in bending 12

[HanStrulo]

Happy Monday everyone,

I have a new challenge and I am not sure how to approach it.
I have a beam in classic bending (max bending at the middle) and I want to install it using bolts.
The beam will come in two sections that i have to join in the middle( where the max moment is). I have never done a bolted connected design for anything other than tension and shear and I have no idea how to approach this challenge.

Any methodology? references? examples?

Thank you

 

[rb1957]

so as I understand it a 24W104 is 24" deep, with 1/2" thick flanges. 24" = 0.6m
the moment is (I think) 800000 Nm, so couple is 800000/0.6 = 1333 kN
You seem to use allowable shear of a 1" bolt as 140kN ... 10 fasteners on each side of the splice ... 40 in all, plus the web splice
ok, so the shear splice has more (many more ?) fasteners than a tension splice
you could save a few by including the moment carried by the web fasteners (may reduce the cap to 8 per side).

Ixx = 3100in4 = 1.3E9mm4, bending stress in beam is 800000000*300/1.3E9 = 0.8*300/1.3 = 185 MPa = 27 ksi ... ok for steel

another day in paradise, or is paradise one day closer ?

 

[BridgeSmith]

I often use a shim (thickness not spec'd) to allow for fitup during erection

I suppose that could work adequately for most beams in buildings. We require more precise alignment control for bridge girders.

We also like to avoid welds as much as possible, particularly transverse welds, to avoid fatigue issues, which I would imagine is less of an issue for most beams in buildings.

It's probably one of those things where we like what's familiar to us, too, so I'm biased towards the type of splice we use for bridge girders. An all bolted splice does seem simpler to me, but then again, I design that type fairly often, so for those who design with end plates, the weld stresses, etc. are probably easy, too. The differences in fabrication costs are likely minimal, although if the splice would be the only welding required for the beam, it could push the cost up some.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[wrxsti]

dik where is the program for the weld stress XD

 

[dik]

Here.... Celt83 provided a bunch of assistance. I've modified it for C, L, T and square/rectangular sections. The data from the pdf file has to be added.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I'm not disputing that... I just cannot imagine that... I think the same precision is required.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[SSCon]

The Green Book will give you what you neeed:

https://www.steelconstruction.info/images/5/5d/SCI_P398.pdf#page=135

 

[dik]

Thanks for the added information.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[HanStrulo]

Thank you guys for all the information.

 

[BridgeSmith]

I'm not disputing that... I just cannot imagine that... I think the same precision is required.

I could be wrong; I don't know. Our fit up tolerance for bridge girders is 1/8" vertically at any point in the span, which are some cases over 200'. It would only take a tiny change in the angle of the alignment of the splice to throw everything out of whack.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Typical building 'fit up' is 1/16" for structural steel and sometimes 'things don't fit'...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BridgeSmith]

Yeah, sometimes things don't fit up right for bridge girders, either.

When you say 1/16", does that include things like elevation at midspan of the beams, too, or just the connections?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Construction tolerances are something else... you might be looking at a foot or so (just joking)... Structural steel when it arrives on site generally has 1/16" tolerance and it generally fits together fairly well. Buildings and other structures may not have or require the 'fit' that bridges have... for example, 'elevation at mid-span' is likely meaningless. The large shim, noted, is to get something to fit between two fixed objects and a little 'wiggle' room is required to get the piece to fit in place... leave a little slack so that it is easier to place... it's not for sloppy tolerance. I normally don't use slip critical connections for moment end plate connections... only if necessary.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I was just thinking (occasionally do). Do you need that sort of fit? You may be paying a lot of extra money for that 1/8" in 200'... just curious...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[DrZoidberWoop]

We usually rent a beam stretcher to solve those problems.

 

[dik]

...done that a few times.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BridgeSmith]

Do you need that sort of fit? You may be paying a lot of extra money for that 1/8" in 200'... just curious...

For spans in that range, it's all plate girders. We include a web cutting and blocking diagram in the details for the fabricator to cut the required camber into the web. After the pieces are fabricated, they line them up in the yard according to the blocking ordinates, clamp the splice plates on, and drill all the holes. In the field, they erect them, get the bolts in the holes, and then do the final vertical alignment by survey before tensioning the bolts. And yes, they are supposed to be within an 1/8" of the expected elevation everywhere. I don't know what the field guys let them get away with, except that when the elevations were off by an inch on a 285' span, they contacted us to figure out a mitigation strategy. It doesn't take much of a sag to be noticeable at 80mph.

Rod Smith, P.E., The artist formerly known as HotRod10