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U-Bolt Clamping Capacity

U-Bolt Clamping Capacity

U-Bolt Clamping Capacity


I need to connect two perpendicular pipe sections together using 2 pairs of u-bolts and a steel plate. I am concern about the capacity of this connection against sliding at the u-bolt and pipe interface. I founded several similar details, stand-off mounts in particular, shown in antenna supporting structure catalog of various manufaturers. But there is not anything about the connection capacity.

Does anyone know any reference on clamping capacity of u-bolt?


RE: U-Bolt Clamping Capacity

Nope.  Use a torque wrench on it.  Convert the torque to tension (yes, I know it isn't exact) but it will get you in the ballpark.

RE: U-Bolt Clamping Capacity

The usual way is to determine how much force you need to resist first, then select a connection.

But it's a simple friction joint.  Clamping force and friction.

If it's an important connection, you should determine these things by test using your actual components.  Otherwise you can guess or use handbook values and torque-tension tables, which amount to about the same thing.


RE: U-Bolt Clamping Capacity

Hi hdn32

Here is some data on torque capacity for U bolts:-


It would be best however if you analysed the max load you can put on the two pipes without crushing them and determine a torque for the U bolt based on that load.

an approximate formula for axial load = P = T/(0.2*d)

where P = axial load

      T = Torque on nut

      d = bolt size

      0.2 = friction factor for dry threads.


RE: U-Bolt Clamping Capacity

Your concerns are warranted big time.

You need clamps similar to these to clamp a pipe as U-bolts don't do a very good job.


RE: U-Bolt Clamping Capacity

In the antenna business, cheap seems to always win over strong, so you may find 'pipe' with extremely thin walls, and with a seam that may or may not actually be welded, and 'plate' that anyone working in any other trade would call 'sheet' or maybe 'foil'.

So the actual clamping capacity of the u-bolt may be irrelevant, because something else in the joint may bend or collapse.


Mike Halloran
Pembroke Pines, FL, USA

RE: U-Bolt Clamping Capacity

Resistance against sliding will be greatly improved if you can also pin bolts straight thru each pipe and backing plate.

RE: U-Bolt Clamping Capacity

I don't have experience with this, but I strongly suspect that if a bar clamp is used correctly, it deforms the pipe, within it's elastic limit, but enough to gain mechanical interlock as well as friction. To slide, the clamp must overcome friction, and, climb up the hill.

Timing has a lot to do with the outcome of a rain dance.

RE: U-Bolt Clamping Capacity

I forgot to say, I expect that the tightening would be by feel, you can feel the grip, when the deformation happens.  

Timing has a lot to do with the outcome of a rain dance.

RE: U-Bolt Clamping Capacity

Thanks everyone very much for responding to my question.

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