Point load for I-beams - I'm building a bridge crane

[ipgenie]

A few years ago I was in a car accident and injured my back. I know that as I get older, I will have to be even more careful not to damage it more so as I've been building my shop, I've planned to include some things to help with lifting. When the pole barn structure was engineered, I included footings to allow for the load that a relatively small bridge crane would need. The space is 11' x 28' with a supporting post at the center of the 28' span. This is a free standing bridge crane in the center of my work space running above my welding table and above a parking/unloading area.

I'm not an engineer and like most of us I'm building this shop on a budget as time and money permits. I have a friend who just offered me some I-beams removed from a large gas station canopy that he replaced. The beams are 12" tall, top and bottom flanges are 4" wide, the web is 1/4" and the flanges are 3/8". There are no markings on the steel but they are coated in a silver paint or other coating to resist corrosion, were protected from weather and are in excellent condition.

The design is a top running bridge crane similar to this image below but with only three vertical posts. My posts are 4" x 8" x 1/4" square tubing anchored to the footings with expansion anchors. The span between posts is 14' centered. I will have to come up with some kind of rail above the beam for the bridge to ride on and I have a heavier 11' I-beam to carry the trolley. I do plan to use some gussets and additional bracing not included in the picture. The timing for these beams is really good as I should be ready to lift them up in place later this winter or first thing in the spring.



I'm hoping for some help determining the load capacity of these I-beams. I have a 1 ton pneumatic hoist that will probably do most of my lifting and I have no concern about the structure supporting that weight but I plan to include another trolley for a manual chain fall and will likely use something with more capacity there. I want to include markings showing maximum carrying capacity and I want this to be reasonably over engineered and as safe as a DIY can be.

Any proper calculations would be greatly appreciated and any suggestions regarding design that will help with safety and convenience would be helpful. I have tried using some of the online calculators but can't seem to wrap my mind around their use, probably because there are so many different ways I-beam is used and each of them are calculated differently.

~Shane

 

[jblnut]

Realistically how much weight do you think you will be lifting ?

No official info below but I also struggled to find charts for what I am doing right now and said screw it, it’ll hold.

Before I started cutting this 30’ long 5.5”x15” 1/2” thick beam I placed it on a 4x4 at each end and set roughly 6,000lbs in the center and measured how much it sank. It sank roughly 1/8” which blew my mind that it was that little. I intend to use it as I span 27’ in my shop as a loft support and was also unsure how to officially test it. I figured it should hold whatever I want to put up there ……


The other beam is a 3/4” thick 11”x18.5” and 40’ long. I put the same 6,000lbs on it and it also moved 1/8” while spanning the full 40’. I think they’ll hold. I struggled to find load charts and stuff so I did my own testing. The green pipes are going to be the legs and are used natural gas line and are 7.5” diameter. I didn’t test them but I’m sure they’ll hold the weight.

 

[readhead]

For calculations it would be helpful to know if the beams are S beams or W beams.

 

[ipgenie]

For calculations it would be helpful to know if the beams are S beams or W beams.

Good question. It looks like a W to me.

 

[ipgenie]

Realistically how much weight do you think you will be lifting ?

No official info below but I also struggled to find charts for what I am doing right now and said screw it, it’ll hold.

Before I started cutting this 30’ long 5.5”x15” 1/2” thick beam I placed it on a 4x4 at each end and set roughly 6,000lbs in the center and measured how much it sank. It sank roughly 1/8” which blew my mind that it was that little. I intend to use it as I span 27’ in my shop as a loft support and was also unsure how to officially test it. I figured it should hold whatever I want to put up there ……


The other beam is a 3/4” thick 11”x18.5” and 40’ long. I put the same 6,000lbs on it and it also moved 1/8” while spanning the full 40’. I think they’ll hold. I struggled to find load charts and stuff so I did my own testing. The green pipes are going to be the legs and are used natural gas line and are 7.5” diameter. I didn’t test them but I’m sure they’ll hold the weight.

WOW, that is going to be a much bigger setup than I will have. It looks like you will have a great setup once it's done.
I'm sure these will be strong enough to carry the weight I have for them but for my own peace of mind I'd like to know how far I can trust them.

 

[readhead]

It is a W beam.

 

[whateg01]

I notice most discussions of I beam capacity center on a static vertical load. If you have it near capacity and push the load to move it perpendicular to the beam, doesn't that have the potential to introduce a torsional load on the beam making it substantially weaker?

 

[ipgenie]

I notice most discussions of I beam capacity center on a static vertical load. If you have it near capacity and push the load to move it perpendicular to the beam, doesn't that have the potential to introduce a torsional load on the beam making it substantially weaker?

I'm not sure how it's measured but I'd agree with you. In this case, any load movement perpendicular to the long beams should result in the trolley moving along the bridge beam rather than sideways movement of the rail beams.
I figure if I can get the point load calculation of these beams, that load would be shared across both rails, more on whichever side the load is closest to but still on both sides. Any side movement would be supported on both rails instead of just one. The bridge will also have a 3-4 foot span on each side also so even the point load would be spread out over a larger area but a point load calculation would be worst case and the additional support will increase the capacity and safety factor.

 

[Beemer]

Look into using a channel cap on your beam section. Beam top flanges without lateral support like you are going to be using it are weak in lateral stability which reduces their load capacity, especially for a beam only 4" wide.. That can be a tricky design problem for people who don't do it for a living. Be careful not to find a beam load table somewhere because they don't apply to the way you are using the beams and will report much more load capacity than you'll actually have due to the unbraced top flange usage.

As visual example of how lateral stability (or lack of it) affects load capacity, stand a flimsy yardstick in end and press down on the top. It will bow laterally with little load. Then very lightly touch (and hold) both sides of the yardstick halfway down the length and retry loading it. That lateral bracing introduced at midpoint will greatly increase the load capacity.
Those principles apply to a horizontal beam too, just turned 90 degrees. The greater the unbraced length, the lower the load capacity.

You'd do well to buy a little professional design help.




PS: The beam/channel combo is something that needs design and not just adding any pieces together.

 

[ipgenie]

I believe I've found the correct parameters for this beam on The Engineering ToolBox website.
The measurements match a W 12x19 beam. I don't have a 12" section to weigh to confirm that it is 19lb but all of the dimensions match as closely as I can measure them so I believe this is correct. Hopefully that helps with any point load calculations.

 

[41plym]

I bought my end trucks from Harrington hoist. I told them the span and they sized the beam for me.

 

[CraigStu]

I am curious how much do you think you might want to lift?

 

[larry4406]

I saved the attached PDF a long time ago from a post here on GJ about building a rolling bridge crane. Maybe it has some useful information for the construction of yours.

Link to a a crane build here:

OldCarGuy’s New Toy Shop

:bowdown: :bowdown: :bowdown: Now I know what I need for xmas

www.garagejournal.com

Here is a pic I saved that was posted by fiftyV8 on All MetalShaping forum of his crane. I don't think he did a build thread on it.

Keep us posted on your progress, maybe a build thread?

 

[strutaeng]

I'm currently working on a project where the owner is installing a 20 ton crane with an auxiliary 5 ton crane into an existing industrial warehouse for fabrication. I'm working with the crane guy, but our scope just foundation design; they are doing all the beam, column, bracing and all of that and just proving the reactions to us.

Spans are typically 26', but some are 36' for special loading/unloading. Building height is like 45'. I believe they are using 14" wide flange columns and 21/24" beams, not certain on the beam shapes.

 

[My Old Tools]

Mine is a simple traveling hoist. It is engineered for 1 ton, dynamic, and the spans are 20 feet between the supports. I would have to go measure the beam dimensions, I can't remember.

 

[ipgenie]

I saved the attached PDF a long time ago from a post here on GJ about building a rolling bridge crane. Maybe it has some useful information for the construction of yours.

Link to a a crane build here:

OldCarGuy’s New Toy Shop

:bowdown: :bowdown: :bowdown: Now I know what I need for xmas

www.garagejournal.com

Here is a pic I saved that was posted by fiftyV8 on All MetalShaping forum of his crane. I don't think he did a build thread on it.

Keep us posted on your progress, maybe a build thread?

Thanks for the information. That chart has a lot of data in it. The pic and build thread give me some great ideas. These guys have some really cool setups, much much bigger than the space I am working with.

In the attached chart I could not find any use of W12x19 but it does show that a 14' span of W10x19 for the bridge beam can carry a 1.5 ton load when underhung. I have a couple of options for my girder beam. I could use a piece of this W12x19 and since it only spans 11' it would be able to carry more than the same size beam can carry as the runway but I think I'll go with a little heavier beam for the girder if only to have a thicker flange for the trolley to roll on. This chart will be super helpful.

 

[ipgenie]

I am curious how much do you think you might want to lift?

My pneumatic hoist is rated at 1 ton and is probably as big as I will ever need, but there is always that one project where you need to lift a little more than you ever have before, just this once, and I'd like to have a really good idea what these runway beams can safely carry so I can make sure the girder beam is marked with the overall capacity.

 

[ipgenie]

Mine is a simple traveling hoist. It is engineered for 1 ton, dynamic, and the spans are 20 feet between the supports. I would have to go measure the beam dimensions, I can't remember.

Seeing pictures and being in garages with hoists like this have always made having one seemed like a good idea to me. I was designing an extension to my pole barn when I was in the car accident and I built most of the structure alone with whiplash, one bulged disk and a ruptured disk. There have been many times when I've wished the crane was already in place, but I'm getting closer.

 

[ipgenie]

I'm currently working on a project where the owner is installing a 20 ton crane with an auxiliary 5 ton crane into an existing industrial warehouse for fabrication. I'm working with the crane guy, but our scope just foundation design; they are doing all the beam, column, bracing and all of that and just proving the reactions to us.

Spans are typically 26', but some are 36' for special loading/unloading. Building height is like 45'. I believe they are using 14" wide flange columns and 21/24" beams, not certain on the beam shapes.

I was in a shop a few years ago with two bridge cranes. The smaller one was about 12' tall, 20'x40' and ran over the entire machine tool area so he could lift things onto his mills, lathes, etc. The other crane spanned the whole remaining shop area. I don't know the dimensions but it was big. He used it for many things but at the moment he had one of the bigger steam tractors sitting in a small part of the shop and was using the crane to repair one of the steel wheels. I had stopped to pick up something he had listed on CraigsList and we ended up spending an hour. It was really cool to see some of the tools and equipment he had and the projects he was working on.

 

[JSGAuto]

Any proper calculations would be greatly appreciated and any suggestions regarding design that will help with safety and convenience would be helpful. I have tried using some of the online calculators but can't seem to wrap my mind around their use, probably because there are so many different ways I-beam is used and each of them are calculated differently.

~Shane

I really appreciate the DIY nature of this, but if you can't understand the calculations from your research, I highly recommend that you hire an engineer. There is more to this then a point load calculation at the center of the beam. Besides your own safety, the liability of anything or anyone that walks under these machines is significant. When structures like this fail, horrible things happen.

 

[ipgenie]

I thought I'd try one of these AI engines to see if it would have an answer. Surprisingly, it gave a pretty detailed answer that may or may not be accurate, but it gives me an idea of the beams strength. Pretty cool.



According to www.iAsk.ai Ask Ai Search Engine:

Question:

What is the point load for a simply supported 14' long w12x19 beam allowing 1/8 deflection?


Answer: (Must be read in a robotic voice )

To determine the point load for a simply supported 14’ long W12x19 beam, we need to consider the beam’s properties and the desired deflection limit.

The W12x19 beam is a wide flange steel beam, commonly used in structural applications. The “W” indicates it is a wide flange shape, and the numbers “12” and “19” represent the nominal depth and weight per foot of the beam, respectively. In this case, the beam has a depth of 12 inches and weighs 19 pounds per foot.

For a simply supported beam, the maximum deflection occurs at midspan. To calculate the point load that would result in a 1/8 deflection at midspan, we can use the formula for deflection of a simply supported beam under a concentrated load:

δ = (P L^3) / (48 E * I)

Where: δ = Deflection at midspan P = Point load applied at midspan L = Length of the beam E = Modulus of elasticity of the material I = Moment of inertia of the beam cross-section

In this case, we are given that the desired deflection is 1/8 (or 0.125) of the span length, which is 14 feet. Therefore, δ = 0.125 * 14 feet.

The modulus of elasticity for steel is typically around 29,000 ksi (kips per square inch), and the moment of inertia for a W12x19 beam can be found in engineering handbooks or manufacturer’s catalogs. For this example, let’s assume an approximate value of I = 58.7 in^4.

Substituting these values into the equation, we can solve for P:

0.125 14 feet = (P (14 feet)^3) / (48 29,000 ksi 58.7 in^4)

Simplifying the equation:

0.125 14 48 29,000 ksi 58.7 in^4 = P * (14 feet)^3

Solving for P:

P = (0.125 14 48 29,000 ksi 58.7 in^4) / (14 feet)^3

P ≈ 6,371 pounds

Therefore, the point load for a simply supported 14’ long W12x19 beam allowing a 1/8 deflection is approximately 6,371 pounds.


Edit to add: Remember, this is not from an engineer, this is from an online AI. It sounds very professional and exact but it may be completely incorrect. Don't consider this to be information that you can actually use.

 

[ipgenie]

I really appreciate the DIY nature of this, but if you can't understand the calculations from your research, I highly recommend that you hire an engineer. There is more to this then a point load calculation at the center of the beam. Besides your own safety, the liability of anything or anyone that walks under these machines is significant. When structures like this fail, horrible things happen.

I agree with you. An engineered structure would be the wisest choice. Many of the DIY builds I see are just based on "Well, that should hold" and I suppose they are often just fine but who knows at what point it won't hold anymore.

At this point I'm kind of in the middle. I have this material to build it at a price I can afford, but I'd like to know how strong it actually is so I can allow for plenty of safety factor and won't be tempted to push the unknown limits. I do have an engineer neighbor/friend who may be able to help with some calculations. I started this thread to get some more information and knowledge from a larger group, knowing that this is still "Just what some guy on the internet said".

 

[larry4406]

But the AI Bot confused inches and feet ?

 

[JSGAuto]

I agree with you. An engineered structure would be the wisest choice. Many of the DIY builds I see are just based on "Well, that should hold" and I suppose they are often just fine but who knows at what point it won't hold anymore.

At this point I'm kind of in the middle. I have this material to build it at a price I can afford, but I'd like to know how strong it actually is so I can allow for plenty of safety factor and won't be tempted to push the unknown limits. I do have an engineer neighbor/friend who may be able to help with some calculations. I started this thread to get some more information and knowledge from a larger group, knowing that this is still "Just what some guy on the internet said".

That's good to hear. The equation you posted is generally correct. I didn't break out the calculator, or check on the assumptions (moment of inertia, ect) For a simply supported beam with a point load. You are designing a structure, so you need to look at all the pieces and how they interact with each other.

The beam itself is not usually the issue when it comes to design (or relevant failures). Just google around, your not going to find many examples of structural failure due to undersized beams.

It's a fun discussion. I just don't want the people lurking to think its that easy and do something dangerous.

 

[ipgenie]

But the AI Bot confused inches and feet ?

That is a little confusing and it's my fault because I didn't specify 1/8 inches in my question.
I changed the question to include inches and the AI spit this out:

Calculating Point Load​

To find the point load for a simply supported 14’ long W12x19 beam allowing 1/8” deflection, we need to solve the deflection equation for the point load (P).

P = (16W^2) / L (d / (5/384) (EI))

Substituting the given values:

• W = 12 inches
• L = 168 inches
• d = 1/8 inch (0.125 inch)
• E = 29,000 ksi
• I = 368 in^4

P = (16 (12)^2) / 168 (0.125 / (5/384) (29,000 368))

P = 35.64 kips

Thus, the point load for a simply supported 14’ long W12x19 beam allowing 1/8” deflection is approximately 35.64 kips.

I don't know what kips is but an online calculator shows this:



A completely different answer than the first time. Probably neither one is correct (15 tons! There has to be an error somewhere) and underscores the fact that these are not real calculations by real engineers who understand the specifics.

 

[larry4406]

Kips is 1000’s of pounds.

I kip = 1000 lbs.

 

[gsmith22]

That is a little confusing and it's my fault because I didn't specify 1/8 inches in my question.
I changed the question to include inches and the AI spit this out:

Calculating Point Load​

To find the point load for a simply supported 14’ long W12x19 beam allowing 1/8” deflection, we need to solve the deflection equation for the point load (P).

P = (16W^2) / L (d / (5/384) (EI))

Substituting the given values:

• W = 12 inches
• L = 168 inches
• d = 1/8 inch (0.125 inch)
• E = 29,000 ksi
• I = 368 in^4

P = (16 (12)^2) / 168 (0.125 / (5/384) (29,000 368))

P = 35.64 kips

Thus, the point load for a simply supported 14’ long W12x19 beam allowing 1/8” deflection is approximately 35.64 kips.

I don't know what kips is but an online calculator shows this:



A completely different answer than the first time. Probably neither one is correct (15 tons! There has to be an error somewhere) and underscores the fact that these are not real calculations by real engineers who understand the specifics.

HIRE AN ENGINEER. you (and your AI bots) are completely ignoring the fact that the beam is not braced for lateral torsional buckling. Your beam capacity is no where near what you think it is. refer to post #9 for ideas of how to stiffen the top flange of the support beam for lateral buckling of the compression flange

 

[ipgenie]

HIRE AN ENGINEER. you (and your AI bots) are completely ignoring the fact that the beam is not braced for lateral torsional buckling. Your beam capacity is no where near what you think it is. refer to post #9 for ideas of how to stiffen the top flange of the support beam for lateral buckling of the compression flange

It's not being ignored and they are not my bots. I tried to make it pretty clear that they are not real calculations and only included them in the thread as a point of interest. No need to start yelling. I'm not fighting with anyone or trying to convince anyone that I'm right about anything.

Perhaps you missed the part about bracing and gussets that are not included in the pics I included from some of the online sites. And perhaps I will hire an engineer. I already reached out to my neighbor/friend engineer and he's happy to help me run some calcs, but that's not the same thing as hiring someone to put their stamp on it. The info in this thread has already helped me be more knowledgeable and prepared for that.

 

[Steve_P]

If I was doing this for myself, I would assume a factor of safety, say 2, and then calculate an allowable point load based upon a maximum stress of 18000 PSI (36ksi/2=18). Randomly picking an allowable deflection wouldn't be how I'd do it. The moment of inertia, I, should be 130 for this beam if I looked it up correctly; this agrees with the engineering toolbox value. You should also take into account the stress due to the weight of the beam itself, which will be minor.
So, at 18KSI allowable, neglecting the weight of the beam, I get 9164 lbf if I did the point load calculation correct.
But, as said, this assumes that the beam is laterally supported, and it isn't in your case; this makes it much more complicated in reality.

You also need to look at the buckling strength of the columns. This is more complicated than a simple beam point load formula, and it's also an easy place to get yourself into trouble; columns fail catastrophically without warning by buckling.

 

[gsmith22]

1. There is nothing in this thread related to lateral torsional buckling and its affect on the moment capacity of your beam that supports the trolley. And that is the governing condition of the beam capacity because it is unbraced for long distances. Its a complex design condition that most engineers struggle with. You are kidding yourself if you think some websites will bring you up to speed.

2. W12x19 are possibly one of the worst members you could use to resist lateral torisonal buckling because the flange width (4") is so narrow. which is why post #9 was hinting that you should throw a channel on top to stop the compression flange from buckling sideways. But its more complex than that. you have to connect the beams to the columns and the columns to the ground so that lateral forces in the beam top flange (destabilizing forces due to gravity) that are trying to buckle it have a load path to ground. If this paragraph leaves you confused, don't move forward without engineering help.

3. at best this thread is going to get you into trouble because it is giving you a false sense of security. hanging 1000 lbs (note that is 1 kip and not 35.64 kips) above your head is deadly.

 

[gsmith22]

If I was doing this for myself, I would assume a factor of safety, say 2, and then calculate an allowable point load based upon a maximum stress of 18000 PSI (36ksi/2=18). Randomly picking an allowable deflection wouldn't be how I'd do it. The moment of inertia, I, should be 130 for this beam if I looked it up correctly; this agrees with the engineering toolbox value. You should also take into account the stress due to the weight of the beam itself, which will be minor.
So, at 18KSI allowable, neglecting the weight of the beam, I get 9164 lbf if I did the point load calculation correct.
But, as said, this assumes that the beam is laterally supported, and it isn't in your case; this makes it much more complicated in reality.

You also need to look at the buckling strength of the columns. This is more complicated than a simple beam point load formula, and it's also an easy place to get yourself into trouble; columns fail catastrophically without warning by buckling.

wrong, you won't get 18ksi allowable because that assumes full braced capacity of a grade 36 steel beam. it laterally torsionally buckles at a stress value way below that. Try finding the moment capacity of a W12x19 at 14' unbraced. (hint: its near 0 and close enough to 0 that for practical purposes is 0)

 

[ipgenie]

1. There is nothing in this thread related to lateral torsional buckling and its affect on the moment capacity of your beam that supports the trolley. And that is the governing condition of the beam capacity because it is unbraced for long distances. Its a complex design condition that most engineers struggle with. You are kidding yourself if you think some websites will bring you up to speed.

2. W12x19 are possibly one of the worst members you could use to resist lateral torisonal buckling because the flange width (4") is so narrow. which is why post #9 was hinting that you should throw a channel on top to stop the compression flange from buckling sideways. But its more complex than that. you have to connect the beams to the columns and the columns to the ground so that lateral forces in the beam top flange (destabilizing forces due to gravity) that are trying to buckle it have a load path to ground. If this paragraph leaves you confused, don't move forward without engineering help.

3. at best this thread is going to get you into trouble because it is giving you a false sense of security. hanging 1000 lbs (note that is 1 kip and not 35.64 kips) above your head is deadly.

This is exactly the kind of info I was hoping would be discussed.

This building was built using pole barn construction. This picture isn't my building, I need to take some pictures, but it's similar in framing design:


In my case each section is 12' wide and 14' long so the taller center bay is quite narrow. This higher place is where I will put the crane.
The building is open from side to side, but has supporting posts holding up the trusses for the center bay and supporting one end of the beams for the wings. The steel 4x6 posts for the crane are bolted to the same footing as the 6x6 fir posts. I dug the footings twice as big as needed (3'x4' and 4' deep poured monolithic with the floor) so they would have capacity for the crane and I am placing the steel posts adjacent to the fir posts with about 2" between, but not attached since the building was not engineered to support them.

Unlike the online pics, I am planning to connect the ends of the rail beams to each other and to include full height gussets to brace them and I have sketches of brace plates running in a Y shape from the posts up along the sides of the rail beams to the top to give some lateral support. I had not considered Beemer's top channel support idea and I really like that. I do have some red iron channel that may work well for that. I believe I could go with a 6" wide channel and still clear the upper side wall of the building (the place where you see small windows in the picture above). Because it is top riding, I can also add any amount of bracing along the web to support the top and bottom flange. This will be much easier to weld in place before the beam is lifted up. Also, the rail that the end trucks ride on will provide some minimal lateral support.

I would love to see some additional suggestions regarding bracing, gussets, etc. that would increase the safety factor of the design. I've been thinking that I should only plan for the capacity of the crane to be what the beam itself can hold and not rely on the additional bracing to increase capacity, but JSGAuto is correct in stating that this is a structure and not just a point load on a beam. If these beams should not be used for this purpose, I can just keep waiting until I find others, but if I can design around these and make use of them, the price and availability are perfect for me. My needs are not for massive amounts of weight, but even a hundred pounds can make for a really bad day if it lands on your lap (or someone else's). If I can (with help) put together a competent design, I may be able take it to an engineer and have them check the calculations for a much lower cost than if I ask them to design it for me from scratch.

 

[NDJ]

wrong, you won't get 18ksi allowable because that assumes full braced capacity of a grade 36 steel beam. it laterally torsionally buckles at a stress value way below that. Try finding the moment capacity of a W12x19 at 14' unbraced. (hint: its near 0 and close enough to 0 that for practical purposes is 0)

So it would fail under its own weight if a bird landed on it ? Sounds a bit extreme

 

[gsmith22]

So it would fail under its own weight if a bird landed on it ? Sounds a bit extreme

A W12x19 with a laterally unbraced length of 14' (distance between support columns) can support its own weight plus a 196lb concentrated load at midspan. So basically if an adult male hung from the beam at midspan, it would have no additional capacity to hold anything else with that 14' unbraced length between columns. so more than a bird, far less than a 1000lbs and not even laughably close to 35.64kips.

 

[gsmith22]

and just to show how flange width matters for long unbraced legths of the compression flange, taking a W12x40 (12" deep, 8" wide flanges) with an unbraced length of 14' can support its own weight (40lb/ft) plus a 2,267lb concentrated load at midspan. yes, the beam weight went up because there is more material, but the distribtuion of that material mostly to the flange width helped dramatically with overcoming the lateral unbraced length of the compression flange between supports. which is why adding that channel at the top flange is a common way to build up a member that supports overhead crane rails where the support beams cannot be braced except at the supports (columns at 14' in this case)

 

[Beemer]

I agree with you. An engineered structure would be the wisest choice. Many of the DIY builds I see are just based on "Well, that should hold" and I suppose they are often just fine but who knows at what point it won't hold anymore.

At this point I'm kind of in the middle. I have this material to build it at a price I can afford, but I'd like to know how strong it actually is so I can allow for plenty of safety factor and won't be tempted to push the unknown limits. I do have an engineer neighbor/friend who may be able to help with some calculations. I started this thread to get some more information and knowledge from a larger group, knowing that this is still "Just what some guy on the internet said".

You can see from the postings that some people understand the implications of unbraced compression beam flanges and hopefully that is of value in your accumulation of knowledge on the subject.

Also be aware that Engineers are educated in and practice in specialties just like doctors.
Someone whose practice is in structural design is who you'd want to sit down with.
You might also find that your Building Dept requires the design of the structure be Engineered and certified.

Good point about "what some guy on the internet said".
That won't fly with the judge if something bad happens.

 

[ipgenie]

A W12x19 with a laterally unbraced length of 14' (distance between support columns) can support its own weight plus a 196lb concentrated load at midspan. So basically if an adult male hung from the beam at midspan, it would have no additional capacity to hold anything else with that 14' unbraced length between columns. so more than a bird, far less than a 1000lbs and not even laughably close to 35.64kips.

WOW, now this is exactly the kind of information I need. I don't know how to run that calculation but obviously these beams are not going to work for this purpose. There must be a way to calculate what adding 6" C channel cap on top would do to increase the capacity (I have enough 6"x2"x1/4" channel to cap both sides) but I have no idea how to calculate that and I'm pretty sure it's not in any charts. I will have to put this on hold until I find some beams better suited to this use.

I have room to use an I-beam with a 6" flange width but the upper walls would not leave room for anything like an 8" flange. If I limit the depth of the beam to 10" I might be able to squeeze an 8" flange but it would be tight against the building along it's full length. Probably too tight of a fit.

gsmith22, I'm curious to know how you would size the beam if you were in my shoes (and I understand that like me, you too are just a guy on the internet).

I have some W10x26 but only enough for one side so I'd have to find or purchase another 28'. Looking at Gorbel Gantry cranes, they rate their mobile gantry with a 13'9-3/16" span of W10x26 at a 3 ton capacity. That is slightly more span between posts than I would have (14' is center to center).





I don't imagine the mobile gantry function would differ much from the fixed bridge crane function but if anything I would expect the fixed position to have less chance of buckling. There is also the added benefit of having the point load spread out over the length of the end trucks vs a trolley hanging directly on the bottom flange. This sounds like a better fit but I'd sure appreciate any feedback.


If anything, this thread is giving me (and hopefully others) a greater desire to have projects like this engineered. There are so many build threads and videos online where guys just seem to take whatever they have and hang it up in the air without seeming to have any kind of load calculation. I would like to figure out as much as I reasonably can regarding this design, then take it to my neighbor and see what his calcs show and then take that information to someone who can put a stamp on it (the shop that engineered the building would be a good option). Hopefully that will help keep costs down and it would definitely be the safest/wisest.

 

[Beemer]

There are so many build threads and videos online where guys just seem to take whatever they have and hang it up in the air without seeming to have any kind of load calculation.

Unfortunately sometimes failures don't happen until years have passed giving false sense of security.
And then the reality of what can happen comes into view.....

 

[My Old Tools]

Fixed has a greater chance of buckling. The rollers on the mobile gantry will give and absorb some of the lateral force. Fixed takes 100% of the force in the member and joint.

 

[helterskelter]

If you're not comfortable doing the load calculations I would recommend buying an already engineered structure. I design lifting equipment for a living and it's easy to miss something. Anyone qualified to design something like this isn't going to provide instructions on a forum. Too much risk.