I am being consulted on some DTI s

[Lutfi]

I am being consulted on some DTI (Direct Tension Indicators) that were installed as follows:

1. ¾ inch diameter A325, for slip critical joints, contractor used DTI
2. Contractor installed DTI under nut which is not the best application
3. Contractor did not use a hardened washer between DTI and nut (turning element)
4. Contractor asked DTI manufacturer to duplicate the filed condition using Skidmore tool
5. Test results from six (6) bolts indicated that only at tension of 34 kips; the feeler gage had refusals to qualify proper tension

Does any one have words of wisdom? There are many bolts that already installed. Your quick response would be greatly appreciated.

Good night

 

[etompos]

Review the DTI manufacturer's installation instructions. If the instructions were not followed exactly, the installation is wrong. It is unwise to put your neck on the line and recommend that a product be used in a manner inconsistent with what the manufacturer recommends.

 

[nerd4life]

Sometimes engineers require slip critical connections when in fact, a bearing connection will work just fine. If you can not find a way out of your problem, research if in fact the connection has to be slip critical.

 

[jonford]

nerd4life has a valid point to pursue, but if you need these joints to be slip critical, then you have a resolve your problem. There are reasons to place the washer under the bolt head and for using the harden washer if under the item being rotated. I don't know which year of the "Specification for Structural Joints Using A325 or A490 Bolts" you are using, either 1985 or 2000, but both have an "Arbitration" section for accepting joints that are questionable. In the 85 Code , it is section 9; in the 2000 Code, it is section 10.

Now having said all that, I just opened the 85 code and Table 4 requires 28 kips for 3/4 bolts. Adding the additional 5% gets you a value less than 30 kips. So your DTI manufacturer says he gets 34 kips, you are allowed to go over, what is your concern? If you question the acceptability of the joints, and I would based on the improper use of DTI's, arbitrate them.

 

[dik]

Is there enough thread to engage a hydraulic loading device used for proofing bolt tension. If there is, the tension can be applied to representative bolts and if they can be snugged down, then the pre-load is inadequate.