piles under tension 1

[rittz]

That is the procedure for calculating vertical reinforcing requirements for cast-in-place-concrete piles under tension. As with steel columns under tension attached to piles with embedded anchor bolts

 

[csd72]

look up the concrete code, I believe that they limit the stress in order to minimise cracking.

 

[rscassar]

Rittz

Can you please try to upload the procedure again, I would like to review and have you provided any specific detailing at the pile cap.

 

[rittz]

kikflip

I did not do a procedure I was asking others to give me one. THe first word in my post was supposed to read "What" not "That" It was a typo. Sorry about that.

 

[TXStructural]

Once you determine uplift on the foundation, compute the area of steel reinforcement required to resist the load. Use appropriate load and resistance factors. Design the concrete as needed for any moments or lateral loads. For axial loads, determine pier size so that there is enough surface area and depth to transmit loads to the soil. Design the rebar as needed for the concrete and load (using the area of steel computed from the loads.) You can discontinue reinforcement as the depth increases and load is shed to the surrounding soil, but doing so generally saves very little in steel and makes the design and construction more difficult. Larger bars mean longer anchor rods.

Lap anchor bolts with nuts and plate washer one development length with the rebar in the footing (use the ld for the rebar.) This assures that the uplift will be transmitted to the foundation. If there is significant horizontal distance between anchor bolts and bars in large piers, use supplemental bars to carry loads from anchor rods to reinforcing bars. ACI 318 App D calculations are not necessary unless there is significant distance between rebar and anchor rods which is not spanned by supplemental bars.

 

[rscassar]

Is the tension force a permanant force such as a cantilevered pile cap or is the tension force coming from transient forces like wind.

The advice I would give is to:

1. Ensure the geotechnical engineer submits an allowable skin friction and confirm onsite for hold down of the piles.
2. For steel columns, ensure that there is sufficient embedment of anchor bolts. This may require embedding an anchor plate if the tension force is significant.
3. For concrete columns, ensure that the column reinforcement is lapped with pile reinforcement.
4. Look at the stress in the reinforcement. I would provide more reinforcement than what is required for strength so that cracking is limited (to some degree).