pile testing rig design 1

[sklgleb]

Hi all,

For those of you who are familiar with pile testing rigs... I am designing one that needs to handle +-600k; the catch is that the contractor asked that I provide a plate through which he will connect his jack to load rig. With the current geometry of the rig, my plate is spanning ~14 inches, and I am taking 16" width to calculate I. Using basic beam theory, I am coming up with a 6" plate thickness! This seems a bit ridiculous. Can anyone point to me to some better approximation methods that would not require doing FEM?

Thanks in advance,

G.S

 

[KootK]

Could you post a sketch showing the geometry, how the load is applied, and the support conditions?

Is there any potential to stiffen the plate? Or would that violate the design criteria?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[oldestguy]

You probably should sketch about what you are using for holding the dials, as well as what the loading system will look like.

 

[XR250]

I could see 600k bending a 6" plate over a 16" span.

 

[hokie66]

The 6" plate sounds about right to me, but I would also like to see the sketch. Make sure you consider stability of the system, as well as strength of the plate.

 

[sklgleb]

Hi all,

Please see the attached pdf. There is a ~3" diameter hole in the center of the plate through which the loading loading rod passes and is secured with a bolt on top ( seems like the rod would have to be made of some super-high strength steel, but the contractor claims 600k capacity). The plate occurs both on top and bottom of the main beams to allow for both tension/compression testing, and also to brace the main beams. Let me know if something is not clear.

Thanks,

G.S.

 

[SlideRuleEra]

There is a ~3" diameter hole in the center of the plate through which the loading rod passes and is secured with a bolt on top ( seems like the rod would have to be made of some super-high strength steel, but the contractor claims 600k capacity).

This is troublesome to me. A 3" diameter rod has a crossectional area of 7.07 in[sup]2[/sup], ignoring any threads that may be on the rod. Allowable yield strength > 85 KSI (600 kips / 7.07 in[sup]2[/sup]) is required. This is far more than the highest value (54 KSI) shown for the high-strength steel used in structural bolts.
Reference Table J3.2, Page 5-73, of AISC Steel Construction Manual, 9th Edition.

There may be an explanation, but I suggest having the Contractor provide suitable written documentation, for your review and acceptance, to support his 600 kip capacity claim for the rod.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Ingenuity]

This is troublesome to me. A 3" diameter rod has a crossectional area of 7.07 in2, ignoring any threads that may be on the rod. Allowable yield strength > 85 KSI (600 kips / 7.07 in2) is required. This is far more than the highest value (54 KSI) shown for the high-strength steel used in structural bolts.

For these applications it is common to use 150 ksi PT threaded bar. Williams Form does a 2.5" dia bar good for more than 600 kips at less than 75% MUTS.

CORRECTION:

3.0" dia (not 2.5" dia) bar is good for more than 600 kips at less than 75% MUTS.

 

[BridgeEI]

Back of the hand calcs looks to be around 6" plate. If that's an issue you can try to get a plate that's a higher grade.

I've had falsework with loads that high and the contractor used stainless steel threaded rod. It has a higher tensile strength, but it comes at a premium if they can find it in stock. They didn't like that they had to use something that pricey but it was their only option. I agree with SlideRuleRra, make sure you get something from the contractor staying they have a rod with an adequate capacity. Those are not fooling around loads should something go awry.