U-Bolt rotational resistance
U-Bolt rotational resistance
(OP)
I have been asked to design a solar panel support for two (2) to three (3) panels approximately 3'x5' each (see attached picture). The panel assembly is to be attached to a horizontal galvanized steel pipe with u-bolts. I am not comfortable with relying on the u-bolts alone to resist rotation of the panel frame, so I want to add a brace to the support post to brace against rotation. This is less desirable than designing without a brace because it limits the degrees of freedom for adjusting the plane of exposure for the solar panels.
Can anyone guide me to literature or design guides for u-bolts that provide industry accepted design limits for u-bolts to resist rotation. I would think that this is done all the time for basic traffic signs, etc.
Can anyone guide me to literature or design guides for u-bolts that provide industry accepted design limits for u-bolts to resist rotation. I would think that this is done all the time for basic traffic signs, etc.






RE: U-Bolt rotational resistance
I would think it depends on how "tight" you make the U-bolt??
RE: U-Bolt rotational resistance
random info:
http://www.truckcomponentsonline.com/U-Bolt-Torque...
EIT
www.HowToEngineer.com
RE: U-Bolt rotational resistance
More direct approach, and it could be adjustable depending on the angle required of the solar panel. Do this all the time in the telecom business at the tops of poles and towers to support antenna arrays.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: U-Bolt rotational resistance
RE: U-Bolt rotational resistance
RE: U-Bolt rotational resistance
EIT
www.HowToEngineer.com
RE: U-Bolt rotational resistance
Always use lock washers or locking nuts. Don't oversize or undersize the clamping plate. You want a little bit of plate bend during U-bolt tightening.
U-bolts are typically A36, HD galvanized.
Use U-bolt pairs, as you get beneficial binding action (not counted for in calculation, but real).
A reasonable approach is to use 30% of yield stress x net section of threads, and a low friction coefficient (like 0.3). This gives clamping (normal to pipe axis). For torque (twisting), F*d.
Provide installation notes on your dwgs regarding range of installation torque. Structural engineers don't usually specify installation torque and threaded fasteners, but this is a good exception.
RE: U-Bolt rotational resistance
Yes, U-Bolts are used extensively in Telecom for that, but where the structure gets too large, as in T-Arms of various sizes, a stabilizing arm is installed from one tower leg to one end of the T. Otherwise, in a high wind, antenna performance is too spotty due to the continuous movement affecting the sector angle.
The solar panels, I believe, are too large for that application, and should have stabilizing arm(s) installed. In all probablilty, if the solar panel frame is stiff enough, one diagonal brace should be sufficient.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: U-Bolt rotational resistance
I think the flat plate that clamps into the pipe, you can find a different one with teeth. Also check the Uni-strut catalog page 109 for a similar U-bolt assembly that might work.
RE: U-Bolt rotational resistance
RE: U-Bolt rotational resistance
So when designing these you would have:
Torque = T
Coef. of friction = u
diameter of u-bolt= d
required friction force = F = T/(d/2)
required Clamping force = C = F/u
This must be less than the bolt tension capacity = 0.3*Fy*Anet (as suggested above).
So in this process you would not consider shear in either direction, because of the clamping force and the 0.3 factor used in the tensile calc, correct?
The clamping force required would be
EIT
www.HowToEngineer.com
RE: U-Bolt rotational resistance
For a 2' microwave or 3' long Tee on a 4" pipe, you can calc a double 5/8" U-bolt to work. And I've seen hundreds in the field that have stood the test of time and high winds.