Hilti Allowable loads into CMU

[ztengguy]

I am designing an angle supporting a concrete beam with hilti Kwik bolts into a CMU wall. I see the loads they give are allowable loads. I have factored reactions from my beam, and designed the angle using factored loads and plastic design.

Now would you re figure a service load and re figure the tension/shear on the bolt and use the allowable loads, or stick with the factored loads, and eat into the factor of safety for the anchor?

Thanks

 

[CELinOttawa]

Always follow the manufacturer's written directions. Do as Hilti tells you to do, and where they are silent, contact their Field Engineering group. Very helpful.

 

[JAE]

Can't you back into your original loads - take off the factors - and determine the service loads onto the anchor?

 

[ztengguy]

Im going to do that, bring them back to service loads and design.
Thanks

 

[Bagman2524]

Sounds like the right approach. The KB 3's have factors of safety of around 4.

“Faith is taking the first step even when you don’t see the whole staircase.” MLK

 

[JLNJ]

I have often thought that in a case like this that if the bolts end up internal to the beam perimeter, then the pullout limit state might not apply and you can use the pure shear load.

 

[TNich]

I see several options but going back through the calcs without the factors is the most precise.

Other options I have used:
1) Contact Hilti
2) Use your factored loads directly against the allowable loads. Yes, you essentially get penalized, but it's only safer than before. You just increase the factor of safety.
3) Use the smallest factor to get back to allowable loads. I.e. if the tension/shear factored load was 1.2DL + 1.6LL, dividing your load by 1.2 would bring you to a conservative allowable load.

2 and 3 are useful to me when it seems impractical to go back through a couple pages of calcs. When it comes to situations like this, I'll never eat into the factor of safety, and will only add to it.

 

[ztengguy]

Thanks. I calculated the service loads. I did notice they are using FS 5 now for CMU application.

 

[GBStruct]

Not to state the obvious, but note also the restrictions regarding installation in fully grouted cells, limit of one anchor per cell, proximity to mortar joints, etc.

 

[ztengguy]

Thanks, yes I saw that also. Its very tough to get anything with significant load to work in CMU anymore.