Splice Connections in Steel Members 4

[KCRatnayake]

What is the best location to have a splice connection in a UB (universal beam) flexural member in a moment frame? This is a floor beam and about 10.0m long.

What is the best location for splices in UB columns?

Any comments are appreciable.

Clefcon

 

[youngstructural]

Try to locate your splices at pints of inflection in the bending moment diagram. With patten loading that's often a bit of a truck, but you can normally get a location with greatly reduced demand in the governing case (say 30% momment and 15% shear when measured in terms of the section capacity).

When it comes to columns you're normally a little more constrained by geometry and architectural concerns, but the principles are no different.

Good luck,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[geoffdale]

I would agree with Greg, however, I would have them design the connections for full moment and axial capabilities.

 

[kelowna]

I do not know if I fully agree with geoffdale. Designing a bolted splice for 100% of the moment capacity can be very expensive, although I agree that even if the actual moment demand is low, the connection should be designed for more.
The Canadian code establishes a minimum of 75% of the moment capacity.

About the connection location, between 1/3 and 1/4 of the span is very typical and it corresponds to BM inflexion points as youngstructural pointed out. In columns I have no experience so I would rather not comment

 

[GalileoG]

Also, you may want to locate them 2 or so feet above the floor level, so when the steel deck is in place, they can easily bolt the splice.

 

[msquared48]

I thought that four feet above the floor level was common now for column splice locations...

Mike McCann
MMC Engineering

 

[lrhg]

Connections in general are expensive.

If the beam is only 10m long, why is it necessary to add splice connections? It would seem reasonable to only have the 2 end moment connections to the columns. Here, too, if the actual moment is less than full moment, consider designing for less as this can eliminate and/or reduce column stiffners and doublers.

 

[apsix]

"If the beam is only 10m long, why is it necessary to add splice connections"
It's part of a moment frame, presumably with welded connections to the columns.

 

[asixth]

I agree with youngstructural, view your bending moment envelope and provide a splice as close to the inflexion point as possible (for the beam that is).

For regular column grid spacing, a good location is 0.3 x Span Length.

Once I know the location of the splices, I even go back to my model and place a pin at that location. In my view, this would be purely modelling a shear splice, however it is still good form to design the splice to transfer some moment. I believe most design codes will have a minimum moment that needs to be transferred accross a splice, my design code, the minimum moment that is to be transferred across a splice is 30% the section capacity.

I cannot comment for the design of column splices. The Australian construction industry seems to have a stigma about multi-storey steel construction that it can't seem to break.

 

[csd72]

I think people have missed the point here. 10m beams should not require splices, only end connections to the columns.

These end connections should be designed for the maximum moment in the beam.

 

[KCRatnayake]

We're facing some logistic issues in using 10m long beams. Site access is so restricted that we cannot bring more than 6m long beams.

asixth,
Is it alright if we introduce a pin at a splice connection which is in a moment frame?

 

[dik]

Kelowna:
Boy am I in trouble... for plastic design I generally design the connection for 25% Mp as required by S16.

I often have splices at length/6 or length/7 locations, depending on the loads... and I nearly always use continuous construction for roofs and not Gerber. It's generally cheaper, connections are easy, fewer pieces to handle, and faster. Deflections are approx 1/3 those for simple span construction. <Off my apple box>

Dik

 

[csd72]

clefcon,

The answer to your question to asixth is no.

Different load cases have different points of contraflexure and the pin could lead to stability issues.

Can the columns be supplied with 2m long welded stubs to avoid additional site connections? - just a thought.

 

[kelowna]

dik
I was refering to S6 (connection to be designed at ULS to the larger of the calcuclated forces and 75% of the factored resistance of the member).
Both the code and the commentary are silent on the reason, but my guess is that it has to do with something already commented by several people
first, with weak splices your structural model changes, creating, in effect, a hinge
second, possible increased deflections.
Regarding the spacing, I have seen about 1/3 to 1/4 very typically

However, any arrangement and configuration will work if designed properly and all factors considered. Who said engineering was a science? More like an art with a few recipe books thrown in for good meassure.

 

[oneintheeye]

would not a full moment connection designed to carry full moment at that location not be adequate?

 

[youngstructural]

herewegothen: It's not a matter of adequacy, but a matter of design efficiency... Anyone can build a safe building that looks like a pyramid; A structural engineer can build you an efficient, cost effective sructure.

I cannot imagine a 75% minimum, even being Canadian. I honestly think New Zealand's 30% minimum is much more reasonable. And it's my birthday.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[oneintheeye]

yes agreed, im talking about splice connections in the beam which is what he (SHE) requires. All this talk of pins forming etc is surely redundant if the moment can transfer the full design moment and so maintain a continuous structure.

 

[hokie66]

Happy birthday, YS! But is this the way to have fun on your birthday?

 

[KCRatnayake]

Many happy returns of the day YS!

 

[GalileoG]

Happy Birthday YS!