Leverage on pillars

[jimbo1962]

If you're hanging a heavy gate on a brick pillar and there is a danger of the gate pulling the pillar over, does it help if the bottom hinge sits in a ground socket instead of a bracket fixed to bottom of pillar?
I know most of the leverage is on the top hinges so would putting a bit of the load into the ground help?

 

[Screwdriver]

Yes, that will help tremendously. If you hang it off the wall, the pivot point will be right at the base of the pillar. If you place the bottom hinge in the ground, even slightly displaced from the pillar, the cantilever effect will try to lift the pillar rather than pivot from the base of it. The pillar still needs to have some strength to it of course and if the mortar is degraded you might even consider fitting a strap to triangulate from (near) the top of the pillar into a ground anchor. (parallel to or also connected to the rest of the wall behind - or whatever else is connected to the pillar.)

Pics would be handy.

 

[gaz1]

if your following the old cast iron gate hinges that have lasted the test if time

the gate ball cup is within the ground for the weight of the gate whilst the top hinge is also there as an aid however the swing of the gate produces forces and needs to be strengthened to hold the gate

2200h x 18 x 11



whilst that pic is a solid stone piece your brick or block post will fail

 

[Pete.]

Whoever I've demolished heavy gates hung from piers there has been a steel box section within the pier and the bricks are laid around that post to make it look like the brick supports the gate.

 

[Hitch]

Whoever I've demolished heavy gates hung from piers there has been a steel box section within the pier and the bricks are laid around that post to make it look like the brick supports the gate.

Exactly this.

Weld a stud with a heavy end cap off the box, build the pier and leave a bit of plate exposed rather than a pre welded hinge if you're concerned about final fitting.
Making the plate the same size as a brick or half a brick makes for a very neat job.

 

[gaz1]

heres the old style gates

Post in thread 'gate post depth?'

Apr 15, 2025

the victorians never needed so deep with there stone gates and cast iron hanging gates and they was heavy

all they did was bury a nice piece of stone 2-3ft deep and use a curved slide piece in the middle

Dia 2200mm H X 18" X 11"



whilst the top hinge is just a hook the bottom hinge is actually within the ground not on the gate post itself

its just a cast iron eyelet that the gate hinge drops into so the weight of the gate is actually on the plate within the ground

• gaz1

• 

 

[Agroshield]

Please see free body diagrams of a gate attached to a pillar and a gate whose entire weight is supported on a socket in the ground.

Sum forces horizontally. Sum forces vertically. Sum moments around the bottom left corner. The gate is static, so all three cancel out.

It is thus not clear how the horizontal forces on the pillar differ between the two set ups.



If you calculate the horizontal force from the top hinge and the vertical weight of the pillar, the resultant of the two should lie within the middle third of the pillar for no tensile forces to be seen in the pillar (https://en.wikipedia.org/wiki/Middle-third_rule)

A cheap way to give the pillar more capacity is to embed a threaded rod in the foundation, put a nut and plate on the top and tension it to about 3 tonne. That compresses the pillar and gives it more bending strength (just like a concrete lintel).

 

[Screwdriver]

It is thus not clear how the horizontal forces on the pillar differ between the two set ups.

It should be intuitively obvious in this case. Your analysis ignores the offset in the system between the two setups.

If the bottom hinge pin is fixed solidly into the ground, it moves the bending moment (i.e. the cantilever of the gate) away from the base of the pillar. How much difference that makes depends on the offset which may be a few inches vs. the length of the gate. The bottom pin itself will also resist bending and take that force away from the base of the pillar.

It all depends on the dimensions; the length and weight of the gate and as @Pete. suggests the structural integrity of the pillar.

 

[Agroshield]

It should be intuitively obvious in this case. Your analysis ignores the offset in the system between the two setups.

The offset is not relevant. You could have one inch between the gate and pillar or one mile. The horizontal force on the pillar is the same.

Please draw a similar diagram to above, balance the forces and moments and show how the tensile force applied to the pillar at the top hinge (which is what generates the overturning moment in the pillar) changes.

 

[bricol]

It should be intuitively obvious in this case. Your analysis ignores the offset in the system between the two setups.

If the bottom hinge pin is fixed solidly into the ground, it moves the bending moment (i.e. the cantilever of the gate) away from the base of the pillar. How much difference that makes depends on the offset which may be a few inches vs. the length of the gate. The bottom pin itself will also resist bending and take that force away from the base of the pillar.

It all depends on the dimensions; the length and weight of the gate and as @Pete. suggests the structural integrity of the pillar.

Afraid I'm with the man with the diagrams.

It intuitively obvious that without the pillar resisting the force the gate puts into the pillar from the weight acting around the bottom hinge, wherever the bottom hinge is, then it will fall over - the mass of the gate will pull it over.

Try it with a removeable top hing pin - the gate will fall, pivoting around the bottom hinge when you pull the pin. That's what the pillar needs to resist.

 

[Pete.]

The top and bottom hinge pins have to be inline with each other or it won't swing properly. You don't want it swinging ino the ground.

 

[Screwdriver]

The offset is not relevant. You could have one inch between the gate and pillar or one mile. The horizontal force on the pillar is the same.

Please draw a similar diagram to above, balance the forces and moments and show how the tensile force applied to the pillar at the top hinge (which is what generates the overturning moment in the pillar) changes.

Tried that and, damn: you're right too. I need to brush up on the dynamics of that situation because (as I have already admitted) that is counterintuitive for me.

FWIW, where I went wrong is an interesting situation where despite a substantial part of the vertical load going into the ground, the maths insists the bending moment (lit. the horizontal force) at the top of the pillar actually works out to be identical as @Agroshield suggests. What I am still not understanding is how a force wanting to bend a pin firmly embedded into the ground does not reduce the force applied at the top of the pillar. My intuition still tells me the mere fact that bottom pin is resisting a bending load means it must be carrying it away from the pillar!

The maths appears to suggest otherwise so I guess I'll have to dig deeper. Thanks for putting me right.

 

[Gareth J]

Tried that and, damn: you're right too. I need to brush up on the dynamics of that situation because (as I have already admitted) that is counterintuitive for me.

FWIW, where I went wrong is an interesting situation where despite a substantial part of the vertical load going into the ground, the maths insists the bending moment (lit. the horizontal force) at the top of the pillar actually works out to be identical as @Agroshield suggests. What I am still not understanding is how a force wanting to bend a pin firmly embedded into the ground does not reduce the force applied at the top of the pillar. My intuition still tells me the mere fact that bottom pin is resisting a bending load means it must be carrying it away from the pillar!

The maths appears to suggest otherwise so I guess I'll have to dig deeper. Thanks for putting me right.

It's because, in your mind, the ground pin/socket is able to take up some moment.

However , it won't actually do that until there is some deflection of that post. That scenario is not covered by the fbd. It's a static scenario. And for this setup,bit shouldn't consider there to be any useful moment taken up by the bottom hinge either in my opinion.

For two reasons;
-the post is brick, it would take significant flex of it to load a sunk hinge to the point it would meaningfully contribute in that way. To the point the post would be damaged/fail.
-the type of lower hinge generally used in these types of gate hinges is a ball/cup that sits above ground. For good reason, a post/socket long enough to transfer moment, below ground, would quickly get filled with water/grit and wear itself away.

 

[jimbo1962]

And if there's any danger of the pillar breaking off about its base, would it help if the top hinge was lowered as far as practical?

 

[knighty]

And if there's any danger of the pillar breaking off about its base, would it help if the top hinge was lowered as far as practical?

it doesn’t really make any difference because the gate itself weighs the same, there's no gained leverage etc.

or... as you raise it up you gain leverage against the post, but then lose leverage in the gate by the same amount

(this is for the post bending... the higher the hinge the less strain there is on it and it's mounting points)

I think... I've not done the maths... ever

 

[indykid]

And if there's any danger of the pillar breaking off about its base, would it help if the top hinge was lowered as far as practical?

As above, the bending moment in the post doesn't change for a given gate size, but keeping the hinges further apart will reduce the force at each hinge so they'll wear less