Gate Post stiffener nonviagra

[Suburbancharlie]

So I've read another post hear ( "How to stiffen my pole? | The Garage Journal" https://www.garagejournal.com/forum/threads/how-to-stiffen-my-pole.258311/ ) and I'm in a similar situation.
The salesman got me, and it truly hurts, as I overkill everything. And I know that it's post flex, as the post is 4' in the ground, with nearly 1,ooo lbs of concrete.
I know there's more than a few engineers hiding in the garage, so hopefully someone can help reduce my confusion and explain to me what the flex stresses are appropriately titled? I've found all sort of formulas and onlinecalculators, but none that are helpful since I don't know what to call the hanging stressor of a gate.

So I was sold 3" schedule 40 (⅛, 11 guage, o.120) galvanized round posts, before I became aware that diameter is far more important than wall thickness. These terminal posts are 10' long, above grade 68". In the ground with a belled out 10" hole, 5' deep, and approximately 3' round at the bottom. They took roughly 18 60lb bags of premixed sakrete, to fill the hole to grade, on top of a few inches of sand and tamped gravel for drainage.
The posts are solid in the ground.
My problem is the inability to go the Deadman route, as the gates swing perpendicular to the end of a side run. And I can't add a header over the double drive gates as the city has a 6' height restriction.
I'm apprehensive to go the "fill it with cement" route first, should it not work, removal is the only option.
The gates are a 2" galvanized tube frame, 7' wide, 5' tall, and are skinned with lumber, the total weight is 150 lbs. Bulldog style hinges are set at 12" and 60" above grade.
I understand that a stiffener ⅛" wall 2½" OD steel tube inserted isn't going to double the "strength" but have a hard time understanding how it won't help? A close fit 10' tube inside a 10' tube (in my mind) should greatly enhance the stiffness at some point?
I'm tempted to try filling the gap between the posts with sand, to reduce the void, and compensate for the inability to weld the tubes together at the bottom. Should this work, I could weld the top seam. If it doesn't, hopefully a shopvac can **** out most of the sand?
I'm my quest for a physics lesson, I've found the appropriate sized post would have been a 4", which has a moment of inertia of 2.755, not that I know what it means, and the 3" is 1.128 added to the 2.5" of 0.637 I know doesn't come anywhere close, but surely there is a better solution than removing these posts, scrapping them, and buying all new!?!? Due to COVID pricing and product availability, this nightmare project is already nearly double the budget, as well as extra months of waiting for materials.
I'll admit, I'm out of my wheelhouse and never had any formal physics education, and honestly never expected a fence to be so darn difficult.
I've read about ITW Permatex Chockfast, and was thrilled to think that might be an option for filling the void as well as sealing the added steel from rust, until I learned it's $300 a gallon.
I've got 5 gates made and ready to hang that are all going to be this way, flexing the 3" post, and looking for help with a solution. Thank you kindly for your time and consideration as well as your wisdom.
I'm unsure what other information might be critical, but I'll happily answer any questions.
And yes, I'll be adding a support wheel near the latch end, but wanting to make sure that the post is stout is important.

 

[mcbane]

How did you conclude the post is flexing rather than leaning? A sure fire way to tell is to put a 4' level against it. If it is flexing it will be curved and wont be in contact with the full length of the level. If it is leaning the level will tell you that.

All posts flex under load but based on your dimensions and 150 lb total gate weight, the 3" pipe is not under very high stress and probably isnt flexing much. My quick calc says around 1/8" deflection at the top of the post. Depending upon your soil conditions, the concrete anchorage may be light.

 

[billconner]

3" schedule 40 steel ("black iron") pipe should be 3 1/2" o.d. and walk thickness very near 1/4", so based on your post, I wonder if you got schedule 40.

I could imagine with gate weight lifted driving something like a square steel tube that fits near perfectly in the pipe but not guaranteed to be stiff enough.

Not even enough room for something like a 1/4 x 4" wide plate welded vertically to pipe, with anchor at away from pipe edge? It could be cut diagonally, so 4" wide at base and tapered to 0" at top hinge. The wider the better but even 2 1/2 or 3 inches might do it.

 

[619DioFan]

Is there room to install a second post next to the first with a foot or so space and then connect the two at the top , mid and bottom ? I had to do this for a 12 foot wide metal gate that the single post was too weak.

 

[BukitCase]

Have you actually ASKED the city if that 6' height restriction is for ANYTHING, or just the actual FENCE height? Built right, a post-to-post "decorative panel" could tie the two gate posts together like a truss... Steve

 

[Half-fast eddie]

Have you actually ASKED the city if that 6' height restriction is for ANYTHING, or just the actual FENCE height? Built right, a post-to-post "decorative panel" could tie the two gate posts together like a truss... Steve

The header has to be high enough for fire trucks to drive under.

 

[Suburbancharlie]

The city won't allow "any part of a fence" to be above 72" in a residential area, and only up to 8' on property against commercial land.
The 2nd post idea has come to me, as I do have a portion of fence between the gate post and the house, and the house side post does sag a little bit less. But I did not want any attachment to the brick house. The opposing side, the gate post is mere inches off the property line and I was instructed not to allow the cement to cross the line due to ongoing issues with the one neighbor.
The 3" galvanized is true fence post, and it's my understanding that there is a difference between the fence stuff and typical black iron, which is why I'm thinking of using true steel, as it sounds to me that fence material is a collection of leftover scraps melted together. I'm hoping the galvanized is just not a strong and steel will work as expected?

I really can't imagine that the 18 60lb bags of sakrete is a light anchorage, in heavy clay soil. The 4' of pipe in the ground is beyond what most do.

Again, I'm unsure what the appropriate term is for the cause of the sag, all I know is that everything was built in alignment and as the pickets are added, the gate begins to droop, significantly.
Without any latch side support (weight helper wheel) the latch side dropped over an inch. Yet the frame remained square.
I'm sure the assistance of a support wheel will help, but am interested in preventing further issues from the gate post in the future. This cement is well on its way to curing (poured over a month ago), and don't want to allow the post to shear off at grade.

 

[billconner]

I think the appropriate term is bending. Any way to check? Drop a plumb bob down pipe and look to see - maybe one of those video things? I guess that it is worth confirming bending.

I honestly never heard of schedule 40 fence post but find it now and much different and smaller than schedule 40 pipe. Now I know.

Based on your constraints, I think after confirming it bent (as opposed to concrete tipping or ???) I would consider temporarily removing gate, straightening pipe, and inserting a 2" schedule 80 (maybe 120) black iron pipe. Inside dia of schd 80 fence post should be 2.47 by charts on line and 2" black iron is 2.375 outside diameter.

Did you consider blocking hinge? shimming bottom away from post or adjusting top to be shorter?

 

[Dumber than lumber]

Diagonal bracing facing opposite direction of the closed gate?

 

[Suburbancharlie]

Well it has not bent "yet", so that's a plus, but as soon as I release it to the demons it won't take long. Currently the gates are uninstalled.

Yes, fence is apparently different, therefore the hope that any true steel inner liner sleeve tube will make a drastic improvement. I'm also hoping that means that fence post junk is not true to steel calculations, meaning there's a far less significant difference in my 3" galvanized and a 2.5" tube, as the moment of inertia for the sizes suggests.

Well the 3" ID has a very ugly interior weld seam down the entire length, causing the 2.5" OD to have an attractive and uniform fit of essentially a 1/16 around the entire area. I know that will be difficult to convince sand down, but again, I'm hoping that the sand would be removable should it not work? And I've been toying with the idea of making a bit of a WD40/sand slurry, to aid in rust prevention.
I'd measured the OD of the stock material at a different fence supplier and nothing I found was as close of a fit as the steel 2.5", as I was hoping for another galvanized post to be less of a corrosion concern.
I'll have to revisit a steel supplier and have a look at schedule 80, as I'm still waiting for the 2.5" shipment to come in.
Also I'm not sure what a blocking hinge is, but I'll happily be Googling that shortly.

 

[PCustoms]

Can you weld on a piece of flat stock lengthwise to the 3" pipe? Put it on the opposite side of the gate.

 

[bugnut]

If it is truly flex not angular misalignment, then a section of angle iron, channel or I beam welded to the 3" pipe on the plane of the hinge points should reduce the flex. A gusset and extension foot on the concrete base will remove even more flex and add attachment to the concrete base.

 

[Suburbancharlie]

So I've now looked at blocking hinges, but I'm not sure how to incorporate that?
The post is 3" and the gate frame is 2", both round tube.

As far as adding materials, that would only be possible above grade. I believe the point of contention to be where the post meets the air?

I'll Google the angular misalignment to see what that means? But I do like that gusset idea.

 

[billconner]

I believe the post is bending at the top of concrete, so I doubt stiffening on outside only above concrete will help. And I can't be sure but no room outside of posts opposite hinge side for any guy or additional steel, not even 3 or 4 inches. And no way to bury or sink additional posts in concrete on any side of existing.

That seems to leave two options for stopping bending. One is internal stiffening as I outlined with 2 1/2" pipe. Perhaps a heavy square steel tube would work and give opportunity to miss welded seam. I think diagonal of 1 3/4" share is close to ID. Install 45 degrees so Z axis is in line with gate.

Stiffening on outside of post and not opposite hinges would only work if gate only swings one direction and might narrow opening a few inches, but a compression member between top of post and concrete opposite of swing anchord to concrete. Lots of options but very thick and/or a flange in edge. Maybe a 6 x 6 x 1/2 " angle with a base plate. Both legs could be tapered from wide on ground to very narrow at top. Grout under base plate and a stout anchor(s) opposite swing side because that's in tension.

I left out option to tear out posts and embed a stronger post.

 

[Jagmandave]

I don't understand why adding the wheel on the end of the gate won't fix your issue? It will take all of the weight of the gate easily....

Some pics of the installation would probably help.

 

[Sumboodie]

3" sch 40 is about .200" thick. Between 3/16" and 1/4".

Find a piece of tube that'll fill in the ID and slide it down.
Or remove it and go with something stronger. Well casing, or structural tube.

 

[afazz]

I coached a friend with a similar scenario (almost exactly!) a few months ago and this is what we came up with. He lived a few states away at the time and has since moved so I never personally visited the property, but he said it worked well.

He jacked the gate up by a little more than amount that it was sagging. The posts above suggesting that there is a "hinge" point at the concrete surface do have some merit, but there will also be bending within the pole so this will help. Welding it in the bent state (by jacking up the gate) helps counteract the static sag.

Warning: the gate will still sag in the open or closed position, this will only stiffen the post in one direction. I don't know how much clearance is below your gate.

 

[afazz]

Also, this can be modeled as a fixed cantilever beam with two loads (at the hinge points). It can be approximated by a single load at the upper hinge point. You're trying to maximize the moment of inertia with respect to the primary bending axis, but also since the gate is a constant force, you can also try to offset this static deflection with a pre-bent beam. Here is a starting point for your Google seminar:

Cantilever Beam Calculations: Formulas, Loads & Deflections

Maximum reaction forces, deflections and moments - single and uniform loads.

www.engineeringtoolbox.com

 

[billconner]

Suburb - what way are you going?

 

[Suburbancharlie]

Thanks for asking.
Well, I haven't decided that yet.
I've been trying to get a hold of the manufacturer to get a better idea of the specifications. It seems that there are a few MTM companies, but they've all told me that isn't theirs?
But in my continued search, I've definitely found that the fence industry is not up to the same standards as steel tube, which means anything I add is stronger than what's there.
Online, of course I've found more formulas that I don't comprehend, but I think I also understand why many people are thinking of it as traditional steel tube, when in fact it is far from it.
In searching for the actual manufacturer, I find many spec sheets, but none to match the dimensions of what I have the stamp of, which is even more complicating.
But I did get some support wheels from Menards, but haven't installed them yet, again, as my concern is to prevent buckling of the installed post.
Hopefully in a day or two a local supplier will get some 2.5" tube so I can waste money on to see if that does anything, although a local weld shop foreman I spoke with today worded it as, "I'm not an Engineer but learned from experience that....." doesn't seem to think my slop fit steel tube will do anything.
I just don't know how the heck I'd get the 1,ooo pound concrete bell out of the ground without absolutely destroying the ground and not have to use 3,000 lbs to make a stable footing for a replacement post. And I can't come up with a means of a quality attachment to this post footing that would allow me to "reuse" it.

I did contact an architect who was a customer, she told me her engineer would call me in a couple days. Hopefully they can confirm or deny my liner tube concept?
I'll also step up my deadman/strongback game on the short return to the house side gate post, to see if that helps any???
Admittedly I have only been working with the neighbors side property line gate (terminal) post, as that's the one I can "disturb" the easiest and not get even more issues from my better half.
So, still in the works

 

[nadogail]

I was able to grab a nice length of I beam from a former employer, years ago, dug a 4’ hole and drove the beam 2’ deeper and filled the hole with concrete. Drilled and tapped the beam to bolt on hinges. It has been 21 years and the gate has not sagged yet.
Pallet beams also make decent gate posts.

 

[FredWanaker]

adding a sprung wheel to pick up load is a good idea if the surface it would run on is firm. So far in my reading in this thread, I haven't heard how we are measuring "sag". How do we know that the frame with the wood isn't drooping or the hinge flexing. I have an old wide gate that was sagging and it turned out to be nothing more than the bolts that held the frame to the post had worked loose over the years.

 

[Suburbancharlie]

I honestly don't know how I'd go about measuring it, but the post is a side property line end (90°) and gate post. The adjacent section of fence has very noticeable movement, while the ground below the post does not appear to budge.
I guess I'll come up with some kind of Jawhorse and level setup and measuring the gap between the "no weight", loaded, and gate swinging open in a variety of positions gap differences?

The ground the wheel will ride on is grass.
The gate frame is 2" schedule 40 (1 ⅞" od) from the same supplier, a 3 rail design, and measuring to remain as square when hung as it is laid on the ground.
Yes, the bulldog style hinges do have a tremendous amount of "slop", but the gate frames were designed with the slop figured in and I left enough swing end to swing end space to allow for a spacer shim to return the gates to plumb once I come up with a plan for ensuring the post isn't going to break on me.
I don't have any specs on the hinges, but other than the frame I built, they are the most stout part of the post.

 

[billconner]

While the wheel should work best at the end furthest from hinge, it might work closer to hinge end, which would require a smaller level track area.

Can you check gate by measuring diagonals flat and mounted, and rule that out or in?

 

[Suburbancharlie]

Bulldog Chain Link Hinges for round posts are an economical alternative to our Pressed Steel ****/Box hinges. Two are required for most single chain link gates, four are required for most double gates. Consider using three Bulldog hinges on gates which are taller than 8' high, or heavy. These chain link hinges will fit 1-5/8" O.D. and 2" O.D. gate tubing uprights simply by moving the collar on hinge. Hinges are very easy to install and may be used on gates which are automated. The larger portion of the hinge shown with U-Bolt simply bolts around the gate post. The smaller portion, or collar, wraps around gate upright. The collar does not fit snug around gate upright, therefore allowing the gate upright to pivot freely. The hinge must be positioned so that one of the horizontal rails rests on the collar. You may bolt hinges just below the top horizontal rail, or build your gates so that they have a longer leg on one side to slide into the Bulldog hinge.

These hinges allow for a 90 degree swivel in either direction. To allow hinges to swing a full 180°, you will need one 180° hinge adapter per hinge. 180° adapters are easy to install. The U-bolts bolt around gate frame, 1-5/8" or 2", and the 'leg' portion simply slides into **** hinge

Stolen from the Hoover Fence site


"Chain Link Fence Gate Bulldog Hinge | Hoover Fence Co." https://www.hooverfence.com/chain-link-bulldog-hinge

 

[Suburbancharlie]

Oh yeah, top left to bottom right is the same as the opposite angle measurements hung or laid down, with and without the lumber.
Checked that a few times.
But as I mentioned, I can watch the ground contact area and up of the post just bend as I remove the shim I have under the gate, and the flex distort as I swing the gate.

I'm currently babying the post till I find a solution, so the other gates are taken off, and the one that is up, is supported, and left untouched

 

[isb cornbinder]

I use ****** regularly. I just show the package to my wife and "she gets up" and makes coffee. I have found ****** improves my hearing. I become very aware of approaching foot-steps. I need only a few seconds "to hide the evidence", so to speak.

Back to reality. I have two swinging gates at the back of our property, . I have set the galvanized posts in concrete.

 

[FredWanaker]

also - a lot will depend on how often the gate is used. Mine for example might get opened 3 times a year. As such, I support it when closed and open, and I am the support in between. If however this is a 3 or 4 time a day gate then it would need to be self supporting 100% of the time. I am curious what the company who sold you the metal has to say.

Also - if you aren't sure if the posts are robust enough, and you are considering digging them up, maybe consider waiting until they show signs of failing before going thru all the trouble. Lots of trees bend in the wind but never fail. Same for posts.

 

[619DioFan]

If the current gate post is hollow all the way to the ground ( bottom of the hole ) I would drop a few long pieces of rebar down and drive them into the earth , then fill the post with concrete. won't cost much and can't hurt. another more radical idea is to find a piece of thicker wall pipe that will slip over the existing tube , weld some brackets to the bottom of said bigger pipe , slip over existing gate post and fasten to the concrete at the base with wedge anchors ( big ones ) then reattach the gate.

 

[ez-duzit]

...Hopefully they can confirm or deny my liner tube concept?...

You're wasting your/their time. Pull out the undersize posts and do the job right.

 

[Suburbancharlie]

Ya, it's a residential gate, and I've never in my life had a fence, so I can say that most of the 5 gates are not going to be opening often, but one of them will be at least a few times a week, the oversized pedestrian gate that fits the riding lawn mower.
I'm really not looking to remove them, should that time come, they definitely will have broken by then.
The seller didn't have much to say, other than "should have used 4", to which I reminded him of the 17' returns I planned to make gate, and the 800 pounds of material he sold me for making the gates. There wasn't anything more to say, he felt the look he was given.

The issue I have with an oversized tube outside of the cement is that would still rely completely on the same potential point of failure in the small post, which is why I am stuck in the belief that only something interior is going to help, like the rebar idea. I'm just apprehensive to go to cement just yet.

Most all the gates won't be used, and have an external (muffler clamp style) hinge.
The self closing fancy pedestrian gate has through bolts that attach the hinges. That's the one that will be getting the most use. I've been wanting to find a provable solution for the vacant posts, before moving on to the most often used one that has the restrictions. Kinda why I have been stuck on the 2.5" round steel tube. I can shove it in, mark the holes, pull out and drill, and then when I battle to put the hinges back on, I'll have some kind of feel that it is somewhat fixed.
The external hinged posts, I can sorta experiment with far easier.

 

[billconner]

I missed you had 5 such gate posts. Before trying one insert, be sure post is pushed back vertical. I think at least for first I'd weld a bar or eye or something inside top of insert so I could pull it out.

A square steel tube that just fits inside might be easier because of less friction and the weld seam.

Either one, I'd also grind a bit of a bevel on entry end.

I got a remote video camera for my phone from Amazon, to look in walls, and if you could it might be useful to look in existing post for obstructions.

 

[Suburbancharlie]

Well as far as I know, there shouldn't be any obstacles in the posts, these were just set at the end of July early August, and for the most part have had the domed caps placed on top.
Again, nothing has changed in that time, so no buckling or kinking has yet occurred.
I guess it is simply me trying to avoid an issue, or prevent a problem before it occurs.

As far as the 5 gates, I may not have mentioned it, because they are all basically the same situation, frames made to the same dimensions and posts set the same way. Yes, if this was just one post, I would have simply scrapped it and chocked it up to failure, but 5,000 pounds and thousands of dollars is a bit too bitter pill to swallow.

Ya, I've been trying to find some way to prove or deny a round is better than square, but the round just hasn't yet come in, and I can't convince myself that all the wasted space around the square is going to be helpful.
I've been searching epoxies and pourable groups, and as expensive as they are, the smaller the void, I think the better off I am?

And yes, have definitely been thinking of means of removal. With a liner tube being in the 60 lb range, I was thinking of just a nut welded inside and a short bolt could be threaded in as a hold, or removed for ease.

 

[bassJAM]

Ya, I've been trying to find some way to prove or deny a round is better than square, but the round just hasn't yet come in, and I can't convince myself that all the wasted space around the square is going to be helpful.

You're probably right. A square tube with the same cross sectional area of a round tube will be stronger against bending moments, but trying to fit a square peg into a round hole means you're giving up quite a bit of cross sectional area to the round tube in this situation so round will probably be better as it's cross sectional area will be higher. That being said, it's going to need to be a VERY, VERY tight fit to work. Like pound in with hydraulic press and hope you don't bend anything in the process tight. Without the ability to weld the sleeve to the post below grade you're relying on a friction fit to make them act as single unit and I just don't see that working.

I think your best course of action without pulling out your posts is to lighten the gates here. Remove the wood skin, or remove the metal frame and build with wood.

You can also try pouring a concrete/mortar in the tube with a high tensile strength. It's a band aide more than a fix but it might help some.

I've looked into this stuff to make an outdoor table out of because it seems pretty resistant to cracking under bending moments without rebar. Heck, you could even drop a piece or two of rebar down the posts and then pack with mortar, it might be a little more resistant to cracking then.

Sakrete Products

Home Improvement Products offers professional grade, easy-to-use, packaged concrete and other products. Our products are designed for D-I-Y and contractor-based home repair and improvement projects.

www.kpmindustries.com

 

[billconner]

The square vs round will depend on wall thickness - which gets most material furthest from center. The plate suggestion was interesting, but it would have to be an "X" welded up. In this case, absolute strongest would be a solid steel round bar for a solid steel post.

I think I might have known fence post was quite a bit weaker than pipe, but now I will definitely know if I'm every installing fence. Thank you for the public service!

 

[Nowater]

If you would consider a counterweight on the opposite side of the post and attached to the gate so that it rotates around the post in tandem with the gate, a counterweight would transform the bending stress to a downward stress. I don't think your posts and concrete will sink with additional weight. The counterweight can be smaller the further from the vertical axis of the post.

I think even a trial of say 100 pounds would be worthwhile.

 

[Suburbancharlie]

The only issue with the deadman/strongback/counterweight is that I'm just a hair off the property line, as I was unwilling to give any of my land to the reason I was essentially forced into having to put up the fence in the first place.

 

[Suburbancharlie]

You're probably right. A square tube with the same cross sectional area of a round tube will be stronger against bending moments, but trying to fit a square peg into a round hole means you're giving up quite a bit of cross sectional area to the round tube in this situation so round will probably be better as it's cross sectional area will be higher. That being said, it's going to need to be a VERY, VERY tight fit to work. Like pound in with hydraulic press and hope you don't bend anything in the process tight. Without the ability to weld the sleeve to the post below grade you're relying on a friction fit to make them act as single unit and I just don't see that working.

I think your best course of action without pulling out your posts is to lighten the gates here. Remove the wood skin, or remove the metal frame and build with wood.

You can also try pouring a concrete/mortar in the tube with a high tensile strength. It's a band aide more than a fix but it might help some.

I've looked into this stuff to make an outdoor table out of because it seems pretty resistant to cracking under bending moments without rebar. Heck, you could even drop a piece or two of rebar down the posts and then pack with mortar, it might be a little more resistant to cracking then.

Sakrete Products

Home Improvement Products offers professional grade, easy-to-use, packaged concrete and other products. Our products are designed for D-I-Y and contractor-based home repair and improvement projects.

www.kpmindustries.com

Oh wow, sorry, I guess I'm not familiar with the quote thing....

So apparently you are familiar with the grout?
I literally just got off the phone with a guy about pourable grout. In my reading I came across a guy mentioning ITW Chockfast. It's an epoxy and has some impressive features. I'd avoided it knowing I'd need almost 4 gallons per post, and at $300 gallon it was difficult to swallow. Well that was the Orange.
Just found out that Red is WAY cheaper and now I'm totally torn. This really looks like an option and it comes in at less cost than the steel tube, leaves no void, requires only mixing and a careful pour.

I'm just trying to figure out how to properly calculate or determine what is best.
This stuff looks amazing.


"Chockfast Red - ITW Performance Polymers" https://itwperformancepolymers.com/products/chockfast/grouting-compounds/chockfast-red/

 

[Walkers]

A couple pics would answer a thousand questions.

 

[bassJAM]

Oh wow, sorry, I guess I'm not familiar with the quote thing....

So apparently you are familiar with the grout?
I literally just got off the phone with a guy about pourable grout. In my reading I came across a guy mentioning ITW Chockfast. It's an epoxy and has some impressive features. I'd avoided it knowing I'd need almost 4 gallons per post, and at $300 gallon it was difficult to swallow. Well that was the Orange.
Just found out that Red is WAY cheaper and now I'm totally torn. This really looks like an option and it comes in at less cost than the steel tube, leaves no void, requires only mixing and a careful pour.

I'm just trying to figure out how to properly calculate or determine what is best.
This stuff looks amazing.


"Chockfast Red - ITW Performance Polymers" https://itwperformancepolymers.com/products/chockfast/grouting-compounds/chockfast-red/

I'm not really familiar with grouts, I just know that concrete is sometimes added to beams to provide stiffness but that's often more with static loads, which isn't what you have so I was thinking the mortar might do a bit better. But the stuff you linked has much better tensile strength @ 1890 psi as well as better flexural strength so if it's affordable that's what I'd try, if anything for one pole and let it dry for the 2 days is says it needs to cure and see what happens. The orange certainly has even better numbers but it sounds prohibitively expensive. I'm still not sure it's the answer, as the vast majority of the strength of a beam comes from the area around the perimeter but I guess it's worth a shot.