LIFT OFF TESTS
LIFT OFF TESTS
(OP)
We are having trouble determining the exact lift-off load on anchors. The bar is a 1.0 inch DSI grade 75. The lock -off load is only 10 kips. We have to wait 48 hours, then perform a lift-off test. The lift off load must be between 9-10 kips. We have a hand pump so it is difficult to pinpoint when the nut lifts off the plate and slows the rate of pressure gain as the entire unbonded length starts extending.
The unbonded length is only 5 ft.(bonded length=18 ft) and we have about 2 ft of free length between the plate/nut and the 120 kip hydraulic jack. I uderstand wire is sometimes used behind the nut, but I don't know the details of that method.
Thanks.
The unbonded length is only 5 ft.(bonded length=18 ft) and we have about 2 ft of free length between the plate/nut and the 120 kip hydraulic jack. I uderstand wire is sometimes used behind the nut, but I don't know the details of that method.
Thanks.





RE: LIFT OFF TESTS
I have never done a lift-off test at a load that low, but it seems like nailing the lift-off load down to within 1 kip would be tough no matter what method you use.
RE: LIFT OFF TESTS
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RE: LIFT OFF TESTS
As for a tell-tale, use a feeler gage and slide under the nut with each increment. Very accurate as feeler gages can be as thin as 0.001", with "off the shelf" gages down to 0.002".
RE: LIFT OFF TESTS