Hello Mr. Ohliger,

I hope I have the example correct.

Yes upon considering the example, I believe there are some scenarios where the "U" bolt, acting in concert with a structure that is in contact with the pipe for some significant horizontal distance would provide rotational restraint.

I believe that in most cases a single "U" bolt can only act on one plane - the plane on which the "U" bolt lays. I believe that when a single "U" bolt is used at a location it may provide only restraint against the three translational movements (and the restraint against the axial movement of the pipe depends upon friction and should not be depended upon to restrain very well).

In the example, if the "U" bolt is oriented on the Z-Y plane it will provide Y translational restraint (support) and Z translational restraint. It will provide some X restraint but only if the "U" bolt is installed very tightly and even then the restraint would be unreliable. If the "U" bolt is holding the pipe firmly against a structure (for example a vertical wide flange column, say a WF14) that is in contact with (along) the pipe for some significant horizontal distance, then the "U" bolt and the face of the column (that is in contact with the pipe) may act together to provide a moment restraint about the Y axis (but NOT about the Z axis).

If I saw a horizontal NPS 4 pipe supported by a horizontally orientated L3x3x3/8 angle (the angle orientated perpendicularly to the centerline of the pipe) with a "U" bolt going over the pipe and holding the pipe and the angle together (the "U" bolt being on the Z-Y plane), I would assume NO significant moment restaint would be provided by this combination of angle and "U" bolt. If however, I see the same scenario but with a horizontal WF8x31 beam supporting the pipe instead of the angle and with two "U" bolts (one bolted through the upper flange of the WF on each side of the web) then I would assume that the combination of the WF with two "U" bolts would provide rotational and translational restraint along and about the axes that were perpendicular to each other and perpendicular to the centerline of the pipe. I would assume NO translational restraint along the centerline of the pipe and I would assume no rotational restraint about the centerline of the pipe (I do not trust friction).

I suppose what I am saying is that there are many scenarios that could involve one or more "U" bolt(s) and each one should be judged individually.

Thank you for the "reality check". I admit I have negative feelings about "U" bolts.

Regards, John.