Seismic embed plate design for gravity beams
Seismic embed plate design for gravity beams
(OP)
Occupancy category IV, Ss=0.89, S1=0.31, 2006 IBC, ACI 318-05, PCI DHB 6e, V=145mph, Puerto Rico, f'c= 5 ksi, 8" cip walls
I'm having some trouble meeting the ductility requirement at an edge condition for embed plates in a concrete wall supporting steel gravity beams. In a field condition, no problem. Even using the 2.5 times the load exception, a few connections are still giving me problems while others are then ok. I'm checking both the ACI appendix D method and the PCI method (fun).
I'm thinking instead to use tail bars, as shown in an example in the PCI DHB 6e page 6-21. My question is in doing so, since the bars are supporting the reaction in tension, would you consider this to be a ductile failure mode so that I don't need to design the bars for 2.5 times the beam reaction? How do others usually handle the ductility requirement vs the increased load?
I'm having some trouble meeting the ductility requirement at an edge condition for embed plates in a concrete wall supporting steel gravity beams. In a field condition, no problem. Even using the 2.5 times the load exception, a few connections are still giving me problems while others are then ok. I'm checking both the ACI appendix D method and the PCI method (fun).
I'm thinking instead to use tail bars, as shown in an example in the PCI DHB 6e page 6-21. My question is in doing so, since the bars are supporting the reaction in tension, would you consider this to be a ductile failure mode so that I don't need to design the bars for 2.5 times the beam reaction? How do others usually handle the ductility requirement vs the increased load?






RE: Seismic embed plate design for gravity beams
Make sure if you are designing from Appendix D, to follow D3.3.3 if need be, thats another 25% reduction, then also making sure you are ductile. The other thing to do is to reduce the number of studs, which brings down your steel strength of the plate, and maybe then will control. (this worked alot in 2003 IBC where you didnt have the 2.5 factor and call it good)
Let me know if my thinking is way off
RE: Seismic embed plate design for gravity beams
I understand that the concrete is being bumped up by 2.5,and 1/0.75 is only 1.33, but it still doesn't make intuitive sense to me.
RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
SEIT, I haven't found an explanation for the factor either, after checking ACI, PCA notes and the PCI. I took it as additional safety for high seismic and important facilities but that's an assumption. In my case for an essential facility, I think it makes sense, but I don't think it would kill them to provide some explanation of where the seemingly arbitrary number comes from. When comparing failure modes, I compared concrete and steel strength without any reduction factors. I think though if you multiply the numbers by the same reduction, then one that was bigger before reduction will still be bigger after.
RE: Seismic embed plate design for gravity beams
Lots of tests have been performed with various results on this...for example see:
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RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
For a tail bar that is welded to a plate, wouldn't the bar-to-plate connection be non-ductile?
Just askin'.
RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
RE: Seismic embed plate design for gravity beams
Would you consider shear friction bars that get developed each side of the connection to be ductile also?
RE: Seismic embed plate design for gravity beams