Reduced Anchor Bolt/Development Length 1

[YankeeeSJR]

I have a situation where anchor bolts need to be developed by using the pedestal reinforcing steel. The height of the pedestal is restricted due to existing conditions and limits on overall foundation depth.
Lets say to fully develop a reinforcing bar in tension requires 30 inches. My bolt/reinforcing "lap" is limited to 20 inches. The "lap" uses the distance from the bolt to the bar, the cover at the top of the ped, etc. Can I use 0.66 (20"/30") of the bar strength fy, 0.9 * Fy * As. The code states that a reduction in development length is permitted for As required/As provided. Can this similar situation be used for Ld provided/Ld required to reduce the tension?
If not, any insight on how to handle this situation? In the past I have utilized a greater number of smaller bars, but this has raised some eyebrows in the field.
Thanks

 

[tincan]

weld a 4" x 4" x 1/4" plate to the bottom of the anchor bolt. Check the resistance. It should make up for the shallow anchor bolt

 

[JAE]

If you have net uplift - then you have to check:

1. That the anchor bolts are strong enough to resist the uplift,
2. That the anchor bolts are embedded into the concrete deep enough to resist the uplift,
3. That the reinforcing in the pedestal is strong enough to take the uplift,
4. That the reinforcing in the pedestal is developed PAST the cone of failure of the anchor bolts,
5. That the reinforcing is developed into the footing below.

I think your original question deals mostly with my item 4 above.

Anchor bolts and deformed bars are never discussed as splices. Each must engage the concrete beyond the failure mechanism.

 

[YankeeeSJR]

JAE,
Thanks for the reply.

The word "lap" was incorrect and Item #4 describes the failure mode I was trying to describe. Items 1, 2, 3, and 5 are met.
The cone of failure is assumed to be at a 45 degree angle from the centerline of the bolt to where it intersects the centerline of the reinforcing. The available development length above that point is less than that required to fully develop the bars in question. What I am doing is using the ratio of available Ld above the failure plane / required Ld to fully develop the bar, to obtain the actual tension force the reinforcing is providing. (available Ld / required Ld) * bar area * Fy * phi = Tension.
Thanks