Tension Tie Beam Steel

[dfitz]

Hello,
I'm designing a foundation for a pre-engineered metal building, 90' clearspan. The mainframes exert approximately 50k of thrust due to Snow, Dead and Collateral. I intend to tie the piers together with a typical tension tie with rebar and mechanical couplers (2#9 bars). I've been asked to use Dywidag rod and their threaded couplers instead of rebar. The Dywidag rod has a higher allowable load (original designer proposed 1 bar), and the threaded couplers are less expensive. Does anyone have experience using materials other than rebar for tension ties? Are there pitfalls associaated with using a high ksi bar in this manner?

Thank you,

 

[KootK]

I would think that this would be fine. One thing to keep an eye on with these systems is that it's prudent to limit the strain in the tension ties as well as to tend to their strength. Usually the high strength bars still have nearly the same elastic modulus as lower strength bars.

 

[XR250]

That is about 1" strain in the rebar based on service loads of 50k. Seems too high.

 

[JAE]

I'd also like to see at least TWO bars used instead of one - redundancy is an engineer's best friend.

 

[dfitz]

Thanks for the feedback. Is there criteria for what the strain should be limited to for this type of application? XR250, is there criteria for what is acceptable? I calculated the same 1" for 2#9 bars, and 2" for the single Dywidag (although using a minimum of 2 bars seems more appropriate). I don't seem to be getting much bang for jumping to high strength bars considering the trade-off with strain.