Deflection of square steel tubing post supported on one end

[Max25]

I'm trying to calculate the deflection of a square tubing post supporting a steel gate. I'm trying to determine the deflection at the top of the post-the free end. Here are the details:

The carbon steel square tubing post is 2"x4"-1/8" wall thickness and 6 feet tall. A continuous hinge will support the door (~6' tall) attached to the 2" side. The weight of the door is 150 lbs. I would like to know if the door is going to create a noticeable deflection near the top of the post.

 

[MikeHalloran]

You'd need to know the width of the door opening to estimate that.



Mike Halloran
Pembroke Pines, FL, USA

 

[swearingen]

A continuous hinge with a 150lb standard (say 3') door/gate on the strong axis of a 2"x4" steel tube is not going to give any appreciable deflection in the tube. What I'd be worried about is the foundation for this post. I'll bet rigid body rotation would account for 95% of any deflection you'd see...


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[rb1957]

really, isn't this a Very simple problem to solve ?

you know the weight of the door and where it acts (1/2 width, no?). therefore the door is putting a moment onto the door post. this moment is applied to the doorpost as a distributed (linearly varying) load; the door weight is also applied to the door post as a distributed (axial) load, which shouldn't affect things much. both loads (the door weight and the moment it creates) are reacted by the foundation. doorpost deflection is due mainly to the distributed moment load.

like swearingen posts, the stability of the foundation is key to the real world results.

this is a static solution; are there dynamic concerns ? (the way my teenage daughter closes her door, there would be)

 

[swearingen]

Another issue that diminishes the effect of the post's deflection is that the hinge is continuous. This means that if the post bends, the door has to as well...


If you "heard" it on the internet, it's guilty until proven innocent. - DCS

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[hokie66]

I agree with others that the footing rotation is the most critical issue. That is what usually makes these things unserviceable.

Remember in checking the post itself that the gate opens, so it has to be stiff enough in all directions. Personally, I wouldn't depend on the continuous hinge assisting. I would apply the gate forces at top and bottom and select the post based on the moment and deflection resulting. That makes it a case of a cantilever with two forces, simple.

 

[kslee1000]

add a small wheel to bottom of the door will eliminate the rotation problem.

 

[Max25]

Thanks to all of you for your great thoughts. Here's what I'm going to do.

10 Pound a rebar inside the square tubing and into the ground for another 2' beyond the foundation and then pour concrete in the tubing with the rebar in side all the way to the top of tubing.

2) Also, there is a 4" pipe that runs underground perpendicular to the post and included in the concrete foundation.

3) Cross bars on the post in the concrete.

Unfortunately, even though I agree that having a top bar that would connect the two sides of the frame would provide much support, it would not go well with the design. But I like the idea of connecting on the bottom; I think that alone will provide some support against the moment discussed by distributing it out and over the tow posts.

Thanks so much for your ideas; I feel much better having talk to you guys about it. Please let me know any other thought you might have.

Cheers,
Max