U bolt Question

[MER3]

Using a U-bolt to clamp a plate to a structural pipe. Assuming both of the nuts on the u-bolt are torqued to the same torque, would the tension in the u-bolt itself be the sum of each of those preloads? For a bolt with a single nut, I calculate preload F from F=kD/T. For a u-bolt with two bolts, would the preload essentially be F= 2kD/T assuming the nuts were torqued equally?

 

[Guest102023]

If the nuts are torqued equally then the load will be about equal in the two legs.
The clamping load on the pipe will be equal to the total of the loads in the two legs of the U-bolt.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[3DDave]

The force applied in a u-bolt is double just like there were two bolts going into a separate clamp. The tension in each leg would be the same as in each single bolt. Actual values might vary considerably because the u-bolt is constrained to by its shape, but were it flexible like rope around a pulley that variation would be smaller.

 

[racookpe1978]

In practice, be aware that 90% (if not more) of the u-bolts over-torqued against the restraint of a simple plate on the other side of a pipe bend the plate. Consider a angle iron or channel if you really, really want to torque on the u-bolt.

 

[tbuelna]

Agree with what 3DDave said. But in reality the nuts of a U-bolt are never tightened at the same time. Usually they are tightened back and forth, and due to factors like friction or bending in the components, the preload in each leg of the U-bolt for a given wrenching torque will not likely be the same.

Just for fun, consider the situation where one nut is installed on the U-bolt by hand until it just contacts the plate. The torque applied to install this nut would be very tiny. Then the other nut is installed and torqued to a much higher level. The installation torque of each nut was far different, yet the resulting axial preload in the respective legs of the U-bolt is not that much different.

 

[Ron]

The torque will be different for the reasons noted. The axial load will be essentially the same in each shank section. The axial stress is additive....the torque values are separate, though not necessarily independent, considering the tightening technique.

 

[BUGGAR]

Think two kids on a teeter totter over the pipe.