AISC 358 Endplate connection with RBS.

[X4vier]

Is it possible to combine AISC 358 Endplate prequalified connection with RBS?
Usually SMF are controlled by deflection and shape required are so strong that D/C ratios below 0.2.
There is any hint on codes than indicated that I can reduce the beam (RBS) to use a smaller but still properly designed connection?

 

[X4vier]

Help!

 

[KootK]

Speaking only to what is rational in my mind, I would think that you could:

1) Design the RBS as one normally would.

2) Design the end plate connection using over strength / capacity design principles to force yielding into the RBS.

As you know, however, just doing what feels rational does not always guarantee performance or AHJ acceptance in this space. One could argue that the RBS and the end plate connections are now one composite "connection" that is no longer prequalified.

 

[Harbringer80]

Is it possible to combine AISC 358 Endplate prequalified connection with RBS?
Usually SMF are controlled by deflection and shape required are so strong that D/C ratios below 0.2.
There is any hint on codes than indicated that I can reduce the beam (RBS) to use a smaller but still properly designed connection?

In my opinion there are more than hints in the code that you cannot alter pre-qualified connections, it's explicitly stated, read chapter K1. I think the code is correct in this one. Ensuring ductility in moment frame connections is unlikely to be successful without full scale laboratory testing.

Options are:
1. Design as ordinary if your seismicity allows for it.
2. Don't use an end plate connection and use an RBS.
3. Select another pre-qualified connection that meets your needs. There are a lot, I doubt your condition is so unique that you need to invent one.
4. Spend a few million and get your alternative connection tested and added to the code.
5. Select a different LFRS.

 

[JoshPlumSE]

Well, it depends on what you mean? You could easily do it for an OMF and no one should bat an eye. But, if you do it for an SMF, then the AHJ may have a problem with your doing this. Especially if this were done for a school or Hospital building.

Personally, I think a lot of other jurisdictions would say it was okay if you make it clear that there was a valid reason for doing this.... like your client doesn't allowed field welding on their site. But, it would still slow down the approval process.

This kind of reminds me of the post Northridge era.... Where you still had to build moment frame structures, but there wasn't yet a code approved method of doing so. We were all kind of working with the AHJ's to come up with something that would satisfy them.

 

[Harbringer80]

Well, it depends on what you mean? You could easily do it for an OMF and no one should bat an eye. But, if you do it for an SMF, then the AHJ may have a problem with your doing this. Especially if this were done for a school or Hospital building.

Personally, I think a lot of other jurisdictions would say it was okay if you make it clear that there was a valid reason for doing this.... like your client doesn't allowed field welding on their site. But, it would still slow down the approval process.

This kind of reminds me of the post Northridge era.... Where you still had to build moment frame structures, but there wasn't yet a code approved method of doing so. We were all kind of working with the AHJ's to come up with something that would satisfy them.

There are all field bolted pre-qualified connections. Just use one of those.

 

[JoshPlumSE]

Harbinger: There are all field bolted pre-qualified connections. Just use one of those.

Exactly the type of argument that a building official might make.

They'd have to counter that with an argument that would be that they are trying use a bolted end plate connection. They just want to reduce the demand on the end plate, panel zone or such.

Honestly, this is a perfectly rational connection. Which is why it reminds me so much of the post Northridge days. This was before Bolted End Plates were allowed and after RBS was allowed. We couldn't do the standard RBS connections because we couldn't do any field welding (customer was a petrochemical plant). The company I worked for at the time chose to use a haunched bolted end plate connection to get our projects done. Following all the FEMA rules for calculated expected moment and shear from the hinge locations.

It was over-kill for certain compared to what we're doing now..... But, so is what the OP is proposing. Rational and I'd be willing to bet good money that testing would easily prove it's ductility. However, it's still up to the AHJ to approve it or not. Many will not. Some probably will.