Steel Embed Plate with Moment

[courtnvm]

What is the most accurate way to analyze a steel embed base plate that has moment and shear? Is it acceptable to design the plate using conventional base plate theory and design the headed studs using PCI guidelines? Any help with this question is appreciated.

Thank You

Val Courtney, PE
Valstone Engineering, Inc.

 

[youngstructural]

How deep is the embedment? Is this into a foundation wall, a floor slab or a stand alone foundation?

Personally in the case of a floor slab, I don't check for shear unless it's a very high shear load. Essentially the load would have to break out a good section of floor in order to be of concern. In the case of a stand alone beam, I design exactly as if it were the end of a concrete beam (stirrups for shear down the foundation, anchor bolts treated as for top and bottom bars analysed as per reinforcing for a beam. With a foundation wall, I combine the two (so long as I have a good load path) since parallel to the wall it is like the floor slab case, and perpendicular to the wall it only works if the base is connected into the floor diaphragm.

I do hope I have correctly interpreted your question!

Regards,

YS

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

 

[UcfSE]

I think what you've stated is reasonable, but you may have issues finding the eccentricity without any axial force present. It might be helpful to resolve the moment into a force couple and go from there.

 

[courtnvm]

I apologize for not giving a little more information. I have an axial, shear, and moment acting on a steel embed base plate that is sitting on a 9" 6000 psi elevated concrete floor slab. This embed plate is the base plate for the stair stringer.

What I did is modeled the embed plates using RisaBase and then followed ACI Appendix D for the design of the steel studs. This seems to me to be an acceptable way of designing the base plates.

Val Courtney, PE
Valstone Engineering, Inc.

 

[courtnvm]

Okay, I have simple question to ask regarding connections to steel embed plates. Is it acceptable to provide a simple shear connection using a shear tab on each side of beam web. What happened was that originally a typical shear tab was provided, but the concrete shear wall was constructed 2" short which made the beam 2" too short. So the fabricator asked if he could supply a new shear plate on the other side of the beam and I said yes. Well they came back to me and said that they have installed plates on both sides of the beam and they want me to bless it. I don't know if this acceptable according to AISC. Any help with this matter would be appreciated.

Thank You,

Val Courtney, PE
Valstone Engineering, Inc.

 

[twinnell]

This is acceptable. Not much different than having double clip angle connection. Make sure you design per the extended shear tab if meets the criteria of AISC.

 

[csd72]

Courtnvm,

one major difference between a shear tab on a beam and a shear tab welded to a solid concrete wall/panel is that the beam will rotate slightly to match the beam end rotation whereas the wall/panel will not.

In this situation I will always design the weld for the shear tab so that it is sufficient to cantilever out to the bolt line. I think you will find a reference to this somewhere is the AISC spec.

 

[WillisV]

csd72 - the welds for shear tabs are (should be per code) always designed to develop the strength of the tab plate anyway (hence the 5/8t weld requirement in the code).

 

[courtnvm]

Yes, what happened was that I was hired to provide structural steel connection design. I initially designed the connection as a shear plate connection welding to the steel embed plate and bolting to the steel beam following the procedures as set forth in the AISC 13th edition.

Then I was contacted by the steel fabricator to inform me that the concrete wall was 2" short and all the steel was already on the jobsite. The fabricator asked me to design another shear plate for him which would weld to the embed plate and weld to the steel beam.

Well now I was contacted by the steel fabricator stating that they welded the initial shear plate to the steel beam also and were needing a letter stating that the connection was structurally okay. It appears to be structurally okay by engineering judgement, but I wanted a sanity check.


Val Courtney, PE
Valstone Engineering, Inc.