bending anchor bolts

[Gorpomon]

Hi,

How do you determine the material length needed prior to bend round bar in to shapes, specifically I'm bending J-bolts and U-bolts with square and round bends.

My problem is in calculating the initial material length to compensate for the bending, are there any references for this anyone knows of, or standardized J-bolt/U-bolt equations. The length of material prior to bending is often called "Developed Length".

If there are no reference tables, should you calculate the circumference of the pin the material is being bent around and then add the straight lengths? Or do you need to get circumference for some point inside the bar to compensate for its deformation?

Any help appreciated.

 

[chicopee]

Concrete forum is your best bet for your questions.

There are a lot of refernces. For example calculation of spring-back for bent rods can be found in strength of material textbooks or ME handbooks.

Developed length calculation can be found under rebar section of foundation textbooks or civil eng. handbooks.

 

[berkshire]

""Or do you need to get circumference for some point inside the bar to compensate for its deformation?""

Yes,
You need to find the neutral line for the material
where the material neither stretches or compresses.

http://www.roymech.co.uk/Useful_Tables/Beams/Beam_theory.html

B.E.

 

[tr1ntx]

There is a direct equation for that, unfortunately I can't find it. I haven't used it in years and apparently it didn't get filed where it should have, so my finding it would be a matter of luckily stumbling across it.

Use 1/3 the diameter as your "point inside the bar" or "neutral line" and that should get you close enough. I mean come in 1/3 dia from the inside of the bend and use that arc circumference for your length.

The actual value depends on the ratio of bar thickness to bend radius and is different for square bends vs. round bends. It also varies with bend angle, but after a certain amount of bend, the variation becomes small, so if you're talking about 90 J's and 180 U's, it's close enough. How close do you need to be? This method should get you within 1/8" on the endpoint of the bar, although I've never verified it on bar diameters greater than 2". (**** Assuming a bend radius of 0.5 to 1.5 x dia)