View Full Version : 6" x 6" I-beam strength?

Deere John
06-14-2009, 03:55 PM
I've looked for tables on this to no result, so I will start a thread in hopes of getting confidence in what I want to use will work safely.

My shop is 20' wide, and I want to bridge it with a 6" x 6" I-beam that I have found for use with a trolley hoist. The beam's dimensions are 6" wide, 6" tall, the top and bottom flanges are each 1/4" thick at the outside, thickening to 1/2" think in the centre where they meet the web. The vertical web is 1/4" thick.

I want to know if this beam will support at least a 1000 pound hoisted load on a trolley that will roll along its length? My gut feeling says yes, with a good margin, but I want to be more sure than my gut feeling. The beam will be fixed in place.


06-14-2009, 04:13 PM
Someone will have numbers but I had the same setup only 24' long that I used for years. I had two electrics on it and each would hold 1000# at the same time.:):)

06-14-2009, 07:14 PM
My program shows 3.21" deflection in the center with a 1000# load in the center and the beam supported only at each end. I used a 6" 12lb ft beam in the program. Hope this helps some.

06-14-2009, 07:41 PM
if you ar only supporting rigidly at the ends i would say no.

you can download a free program called beamboy that will let you play around with various sizes.

06-14-2009, 08:01 PM
if you ar only supporting rigidly at the ends i would say no.

you can download a free program called beamboy that will let you play around with various sizes.

Beamboy is what I used for his.

06-14-2009, 09:42 PM
The beam you describe is most likely a M6x20. This is an I shaped beam, 6" tall, 5.938" width with a 0.25 web, 20 lbs per foot. Moment of Inertia about X axis is 39.0 in.^4.

I am not an engineer. If you want a definitive answer, you'll need to ask one.

My calculations show that a 1000 lb load hanging at the center of a 20 foot beam with the beam simply supported at each end will deflect (sag) 0.25 inches. The calculation is linear so for each additional 1000 lbs the beam will deflect an additional .25 inches.

What I can not tell you is at what point the beam will buckle and fail. Be aware that any sag in the beam causes a potentially dangerous condition if the trolley is not at the center of the beam and it rolls down the sag to the center under load.

You can always put a temporary jack post under the beam if the trolley is not at the center to take part of the load. You can also attach clamps to the beam to keep the trolley from rolling.

06-14-2009, 10:12 PM
I just downloaded Beamboy and it calculated the same 0.25 deflection.

What values did you guys enter for the beam?

06-14-2009, 10:53 PM
Chumly2071, please pick up the nearest white courtesy phone. :)

LW Hiway
06-15-2009, 03:44 AM
I used something about that same sized beam, but doubled them as a bogey about 24" apart, but would roll the length of the shop as one with crossed braces and double dolly hangers for the hoists.

I'm thinking we could or at least had, picked up about 3,500 lb with nothing breaking.:rolleyes:

06-15-2009, 03:55 AM
I had forgot and was reminded that mine (24') was attached to 2"x6"x1/4" steel tube rafters every 4'. It was an H beam instead of an I beam. It may have had some sag, but I never noticed it. It for sure never had enough that the trolley would move on it's own.

When I was in high school, I had a long battle with a physics teacher about whether a fly landing on a rail road track would bend it.

Another about would there be sound if a tree fell in the forest and no one heard it. (I did not understand this one till I took geometry in college)

He assigned me a semester paper to write on why a butane tank was round instead of square.:):)

06-15-2009, 10:51 AM
If it is just a fixed position beam, it my be possible to add a tri-angle shaped truss on the top edge. Last on I did, 23' span, there was lots of room in the attic, so we built a bolt on/bolt together truss, so as not to have to mess with the sheet rock so much.

The truss members are in compression, so we used 3" x 3/16" wall square tube. Basicaly, we just copied the "W" design of the wooden roof trusses. Much harder to figure the deflection of a truss, but it sure made a large difference over the 6" beam alone. Quad-drupled the studs under each end of beam, plus some plywood and angle iron to tie the beam to the walls. mark

06-15-2009, 06:06 PM
assuming a completely static load condition, a 1000# load at the center of that beam ( i used data for a W6X15) would net about 3/8" deflection, and about 6200 psi bending stress. assuming 36000 psi beam, this is a decent safety factor.... now you need to take into account any potential side loading , or pulling off angle in any direction other than along the beam's length. this can create a buckling condition, and should be avoided (not as much of an issue if the beam is set up with a trolley like a shop hoist that can traverse the length and width of the shop...)...

Anyways, if this is to be used anyplace where you will have employees or customers around for lifting, I'd get a sign off from a PE for insurance reasons.

hope this helps.

06-15-2009, 07:31 PM
Now that is a good teacher.
I bet you still use what you learned.

06-15-2009, 11:36 PM
dont forget to size the end columns to take the side load (buckling) and the slab they bolt to/set in

there are a ton of these things out there built to satisfy varying peoples ideas, as well as tons of engineered ones.

it really comes down to what you are comfortable with. build it and test it.

i think anything more than 1/4 deflection at center span with double the rated load is too much, beams are pricey but not overly so. and trussing is a very good option.

i have only seen one fail and it was at the end column.

now if you can add support to the dead center .............

i myseld am on the hunt for a 23-25 foot bridge to put in the shed .

i have the beams to use for the travel, i want 2500 lbs over my whole shop.

Deere John
06-16-2009, 05:46 AM
Thank you all for the relies. My shop is 17 years old, but has a new concrete floor, 6" thick, re-bar laced. The beam ends are supported by vertical 6x6 timbers, 117" from the floor. Each 6x6 timber sits on a horizontal 6x6 timber that spreads the load over 32" of the floor, and the beam is braced sideways in the walls.

If I understand the above replies, my 1,000 pound load will deflect the beam about 3/8" in the centre, but will provide potentially a 6:1 safety margin?

My hoist is rated at 1,300 pounds, so that will be the max, and I can either build a compression truss on the topside (good idea!), or just use a pitprop for those few times that the load actually does approach 1,000 pounds.

The loads will mainly be ATV's, snowmobiles, snow plows for the trucks and backhoe buckets when the backhoe needs another bucket but is away from the shop. All of these are in the 5-800 pound range. I think I'm good to go.

06-17-2009, 06:04 AM
in a purely static load case, yes. any loading other than vertical, and the above calcs are not as valid. Also, the "safety factor" you mentioned is based only on the bending stress of the beam. In a different world, the deflection is a concern, as is the possibilities of loading in directions other than vertical.

Deere John
06-17-2009, 07:51 AM
OK, thanks - I understand what you mean. The starting and stopping moment of an electric hoist would be such an example of a dynamic load. I don't expect any side loading, unless a load should swing on the hoist and pull the beam side to side.

When I was at work yesterday, a co-worker suggested that I get two pieces of 1/4" x 4 to 5" flat stock, each 20 feet long, and reinforce the web on either side by continuously welding the stock to the web. Seems logical to me, as I will never support more than 1300 pounds plus the weight of the trolley and hoist on this beam. Does this sound reasonable? This is in my own shop, and it is not a commercial venture where members of the public will be expected.

Thanks again.

06-17-2009, 11:35 AM
1/2 ton is a nothing load, as far as end bearing on the floor; 500 lbs on each end, plus one half the weight of the steel. Standing on on foot, I exert more pressure than the hoist will create. Easy to get carried away, but I am a big fan of spreading the load in wooden structures, with glued plywood and steel. Don't want the beam ends to act "naughty", get a solid connection between steel and wood.

You can stiffen the side ways on the beam with a flat plate or buy an H-beam, or buy adding a horizontal truss, you could even use cables under tension. :D If I wanted to add horizontal bracing, I would bend some 10 gage into a ~2 foot wide shallow channel. Then drill a series of holes in the 10 gage, and Plug weld the plate to the top flange.

Most likely, I would tie the top flange of the beam to the ceiling structure, in several places, with flat straps. The straps would flex, so the vertical beam deflection is not transfered to the roof, but sideways movements would be resisted. But it is only 1000lbs! mark

06-18-2009, 05:07 AM
Too bad you are so far away. Most home shops here use farm tool bars for the main beam. The farmers bend them and they have to be replaced so a scrap 25' or even 30' long is common. These things run to 40' on the tractor.
The tractor has the power to bend them if the operator makes a mistake on a turn or something. Usually they are 5"x7" and run from 1/4" to 1/2" sidewall. You have to make new sides for the trolley to get the drop. I am going to put up a 3/8" one 24' long. I don't know what it will hold but it is enough. A downside is the clearance for the trolley on top, you loose some total height.
I will start another thread but I have been putting a jib over the mill and lathe and it is made of barn door track. It will hold one drill and have the ability to lift a rotary table of about 90#:):)

06-18-2009, 11:03 AM
I forgot to mention that the brackets that fasten the ends of the steel beam to the building, should have slotted holes (with "loosely tightened" bolts). This is so that as the beam "shortens" in length, due to load induced deflection, it doesn't pull on the walls. The length change is very little, as is the difference in expansion and contraction due to temperture change, but it is a nice detail to allow for.

I have used a ~4 foot length of angle, lag bolted horizontaly to the wall studs, that bolted to the bottom of the I beam, (on each end of course). The wall was also beefed up with a sheet of 3/4" ply glued and screwed to the wall area under the each beam end. The idea, of the angle iron bracket, was to resist any tendency for the beam to rotate. This isn't that big of force, but a swinging load does twist on the beam. Also, McMaster Carr sells the wedge washers that make bolting thru the I-beam flanges "tidy".

Deere John
07-14-2009, 06:31 AM
Thanks guys for the help. I'm attaching a picture of the beam in place, after the beam clamp was removed. It will be great for whatever I'm going to lift, and is held in place with the slotted hole idea.

07-14-2009, 10:17 AM
im glad you came back and posted pictures for us. :)

07-14-2009, 02:02 PM
Thanks guys for the help. I'm attaching a picture of the beam in place, after the beam clamp was removed. It will be great for whatever I'm going to lift, and is held in place with the slotted hole idea.

Can we call that a load test? :p

Deere John
07-15-2009, 05:52 AM
Pretty much - the paint and the rolling trolley were the load test - good enough for the girls I know. :D

07-15-2009, 11:49 AM
I have two beams outside my shop on a covered area. Photos enclosed.