Beam bearing on cast in plate 1

[Veer007]

Hey guys,

I have a case where beam W690X192 bearing on cast in plate at both ends, which has 6000mm(unbraced length) span with 1550kN.m moment force per beam selection table if I go with full moment capacity of beam.

Can I divide this 1550/2 as this supported on both end? So that I have 775kN.m

Is this fine?

Thanks in advance!!

 

[jayrod12]

Shouldn't you just put through the RFI to the EOR?

Who's to say there isn't a brace somewhere allowing the unbraced length to be 3m or 2m.

Quick RFI should answer your question. They'll likely default to MAX UDL/2. But if that value is too high for you, then you could ask for the actual loads.

Are you designing the bearing plate? Or just the connection from the beam to the bearing plate?

If the latter, why does it matter? If there's uplift, or lateral loads at the connection, that direction would need to come from the EOR, and if not then it's all gravity and you just need to provide enough of a weld to keep the beam in place during construction.

 

[BAretired]

I don't understand the question. Why would you divide the moment by 2 because the beam is supported at both ends? Doesn't make any sense at all.














BA

 

[MIStructE_IRE]

I thought it was just me BA.. I read this 5 times and assume I must be missing something as this makes no sense to me whatsoever

 

[BAretired]

Hopefully the OP will clear it all up for us, MIStruct.

BA

 

[Veer007]

Aplogies for the inconvenience..

I got this moment value from CISC along with length of beam which is so high...

That's why I asked, can it be divided by 2 as it's reaction to be udl/2

Is it wrong?

Thanks in advance!!

 

[Veer007]

There is no uplift force, just have to connect for its actual reaction..

Yeah I have to determine Bearing plate to beam weld..

Thanks in advance!!

 

[MIStructE_IRE]

I’m still unclear. What has the moment capacity got to do with a cast in plate?

Perhaps a sketch would help clarify?

 

[Celt83]

If your connecting to cast in plates on both ends of the beam make sure you allow for one end to have some slip. Any temperature swing after the beam has been placed will rip one of the embeds out to the wall if it is rigidly attached to both of them.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[BAretired]

I don't know what grade of steel you are using, but my CISC handbook lists W690x192 (G40.21 steel) as having a factored moment capacity Mr of 1540 kN-m at an unsupported length of 6m and a factored shear capacity Vr of 2230kN.

If the beam is uniformly loaded to full moment capacity, then W_f*L/8 = 1540kN-m, so W_f = 1540*8/6 = 2053kN where L is the span and W_f is the total factored load on the beam. That means the factored reaction Rf = 1027kN at each end. Whether this is your situation or not, I cannot say. These are very large values, and should be confirmed with the EOR as suggested by others.

BA

 

[jayrod12]

CISC version 11. Page 5-38. Total load on a 6m W690x192 = 2670 kN. UDL/2 would equal 1335kN. But again, I highly recommend querying the EOR for the actual loads.

 

[Veer007]

I don't know what grade of steel you are using, but my CISC handbook lists W690x192 (G40.21 steel) as having a factored moment capacity Mr of 1540 kN-m at an unsupported length of 6m and a factored shear capacity Vr of 2230kN.

Steel material is 350W

Thanks in advance!!

 

[Veer007]

just to be clear using UDL to determine Reaction force whereas Using moment force to determine reaction force, actually which one is more efficient?

Thanks in advance!!

 

[jayrod12]

It doesn't matter which one is more efficient. It matters which one the EOR is expecting/needing.

And as you can see by the two calculations between BA and I, it gives a different answer. I'm this case, 30% higher.

If you would've put in the rfi yesterday morning you might've gotten a response already.

 

[BAretired]

There is a reason for the difference, jayrod12. Your result is based on a laterally supported beam and is correct for that condition. My result is based on a laterally unsupported beam spanning 6m which was one of the stipulations in the OP.

I cannot dispute the suggestion that the OP should question the EOR about the factored reactions to be used.

Using moment force to determine reaction force, actually which one is more efficient?

There is no question about efficiency. Bending moment is used to generate load, then load is used to determine end reactions. The difference between the two results is due to lateral bracing considerations. They are both correct, one for a braced beam, the other for an unbraced beam.

BA

 

[jayrod12]

There is a reason for the difference, jayrod12

Oh, I'm aware of reason behind the difference. But based on the questions we have received from the OP in previous posts, and the information included in this post to date, I would be hesitant to assume anything and therefore would be defaulting to the larger load.

And who knows, this 6m unbraced length beam may be loaded by an off centre point load causing higher shear on one end but staying within the moment capacity. There just isn't enough information given so far. And I'm getting rather tired of having to ask for it all in order to formulate reasonably accurate responses. And if it is uniformly loaded, what is loading it and why can't you consider the top flange braced then?

And lastly, if this beam is in fact just gravity bearing, then again I say that any sort of connection will likely be adequate between the beam bottom flange and the cast-in bearing plate. If there's no lateral load, and no uplift, the connection just needs to keep the beam in place from accidental hits to the bottom chord, and/or construction loading.

 

[BAretired]

No argument, jayrod12. Hopefully the OP will fill us in on some of the details.

BA

 

[Veer007]

Guys, thanks for the info.
I have raised an RFI stating that we need actual reaction force. So far I have not received any response.

For this case, 2 columns will be supported over a beam and we used UDL load to determine reaction force at both end.

How can we separate beam is braced or unbraced?

Thanks in advance!!

 

[Veer007]

Guys I got response from EOR, dead load 975kN, Live load 300kN and SL=80kN...

Thanks in advance!!

 

[jayrod12]

So a factored reaction force of 1710 kN. Good thing you asked since that is higher than either of the methods.

And this is why, for all the young engineers that are lurking on this forum, you should always list your reactions on your plans.