beam splice

[wrxsti]

if i want to do a mep beam splice
and i design the mep for the moment in the beam per say and not the z of the beam

do i need to go back in my structural analysis software and change the section of the beam
at the splice for a z comparable to the mep?

 

[jayrod12]

Maybe I'm the only one, what's an MEP splice?

 

[wrxsti]

moment end plate

sorry

 

[jayrod12]

Ah yes,

I would say no. But then again I don't deal in seismic region so that may have a different answer based on that. However I feel if the splice itself is designed for the maximum moment it is going to see in it's lifetime (with the appropriate factors taken into account), then I don't see why the model itself would need to change. You're providing the required continuity across the connection.

 

[wrxsti]

yea i havent tried it

im not sure if the moment would change

like how it does with redistribution when you vary the Z at center and ends like in
moment frames

 

[jayrod12]

Why would it change? As I said, if the splice is designed to transfer the maximum moment that would ever exist at that location, it would be sufficient to transfer any re-distributed moment across it. Just because your beam is "weaker" for a short instance doesn't affect the ability to transfer the applied loads across a properly constructed/designed splice.

Full moment splices when not required are wasteful.

 

[CANPRO]

There might be some confusion with terminology still. What section property are you defining with Z? It sounds like you're asking if the change in bending stiffness at the splice location will make a difference to the overall structure.

Estimating the stiffness of a connection is difficult, and likely not all that accurate. If this is what you are asking, I have asked myself the same question. The short answer is, of course the stiffness of the connection will make a difference - on the extreme end of things, if your end plate moment splice was closer to a pin connection, you'd have a hinge in your beam. If you have a well proportioned connection, I don't think it would make much of a difference. By this I mean, if your design only requires the splice to handle 10% of the beams bending capacity, I would design for something closer to 50-75%. I'm just throwing some numbers out here with my gut feel, if someone has any clear direction on this I'd love to see it.

The way I typically deal with this kind of uncertainty is to run a couple "sanity checks". In your model, at your splice location, insert a short member say 100mm long into your main member (or a node with a rotational spring)...and then you can play with the stiffness of your connection and see how it impacts the global behavior.

 

[wrxsti]

thanks for the answers guys

@jayrod12 "Full moment splices when not required are wasteful" yea it the connection for full moment looks ridiculous
when you look on the ones used in some of the already built pembs ive looked on

@CANPRO yea it begs the question

 

[wrxsti]

how do you create a same depth moment end plate connection
for full capacity of the beam

when M/d will probably always be greater than σ * tf * bf

since the design of the flange welds and bolts
revolve around M/d

 

[dik]

Something like...

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

-Dik

 

[dik]

and... Doesn't like my file naming...


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

-Dik

 

[dik]

how do you create a same depth moment end plate connection

You may no be able to, or maybe with very thick end plates and lots of bolts... I usually only connect for a small % of the Mr.

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

-Dik

 

[wrxsti]

dik i guess youre analysis can help a bit more since you consider moment capacity for the web weld

whilst the aisc examples are coming up with a flange force

Ff = (M*12)/(d-tf)+P/2

this concept limits the capacity of the connection
by the amount of force that can be transferred by the flange
versus working with the Z of the section

 

[dik]

wrxsti... check it prior to using any parts of it... I have another SMath for weld pattern that I use as a check...

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

-Dik

 

[wrxsti]

the same one you had uploaded previously?

 

[dik]

Should be... I don't recall editing it...

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

-Dik

 

[wrxsti]

cool thanks alot dik

what is your opinion on the methodology on relying on the flange weld alone for the moment?

 

[CivilStructural01]

The tensions bolts will deform, calculate the elongation

 

[dik]

Yup... but will have a minimal impact on the limit load...

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

-Dik

 

[dik]

Flanger weld provides most of the flexural moment... but I still like the web too... My moment splices are at nearly 1/7 pt... and shear tends to be higher.

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

-Dik