Epoxy Suggestions

[RM87]

Hello folks,

I was wondering if someone could give me some quick advice. I'm designing a partial seismic retrofit for a small two-story home - and I'd like to further fasten the existing 4X mudsill to the existing concrete foundation/stem wall. I'm assuming the following:
Cracked concrete
1,500 PSI unreinforced concrete
150 PLF max distributed uplift based on a simple seismic overturning calculation

I looked into Simpson Strong-Tie products but a lot of their values are based on f'c = 2,500 PSI and I'm not comfortable using some iterative calculation to justify lower values.

Any thoughts?

Thank you,
R

 

[ztengguy]

I would have the concrete tested to see if really 1500 psi. How did you come up with that number?

 

[CELinOttawa]

1500 psi is really very low; Test results could come back far higher, but depending on what you need to do, the current compressive strength should not be used in design. All our design and practice is based upon the characteristics of concrete modelled on the 28 day compressive strength. There have been some spectacular screw-ups based on designing/modifyind structures as if the in-situ ASTM42 test results could give you an indication of deflection, creep, durability, etc.

I usually assume a different 28 day strength depending on the age of the structure and the quality of the workmanship. Test results must be used to confirm this in any and all critical applications. Where you're talking about new anchor bolts for a seismic application, I'd assume a fairly low value and then recommend confirmatory tests. I would not bother to insist on the tests prior to design, but I'd make sure to keep spare capacity in the "back pocket" in case it comes in low.

Make darn sure you select a seismically rated expoxy!

 

[EngineeringEric]

At that value, you may be able to argue using Grouted Masonry design values. (f'm of 1500 psi)

 

[ameyerrenke]

you can input custom strengths in the hilti program.

 

[RM87]

Thanks for the information. If it makes any difference, California Existing Building Code prescribes the strength for unidentifiable existing concrete as 1500 PSI (Table A1-D).

@EngineeringEric - That was the approach I initially used, and I'm sure I can argue it but do you happen to know one that doesn't require masonry?

@ameyerrenke - I'll check out the Hilti program. I was looking around yesterday and some of the community were referencing it.

@CELinOttawa - Will do. I'll keep my eyes peeled for seismically rated epoxy. Thanks

 

[ameyerrenke]

some of the Hilti epoxies are seismic rated FWIW

 

[structSU10]

The problem is ACI 318 explicitly states it cover concrete with 2500 psi strength and higher (1.1.1 I believe). That is likely why you don't see values lower than that, and many programs will not allow you to calculate capacity at lower than 2500 psi.