Bridge Crane designs and ideas...38' span

[Egon]

Other folks have mentioned quite a few rather important details involved in bridge beam design. The tables you see may only be applicable to a complete component design of the company issuing them. Any deviation from that design negates their use.

Look at concrete beams. Gives a very good description of the compressive and tension areas of a beam. Those compressive areas could be considered a column. The beam web may also be subjected to buckling.

 

[Streetcar]

Euler formula is a method of calculating the torsional buckling of beam column.

 

[LD1]

Euler formula is a method of calculating the torsional buckling of beam column.

Correct. Not a horizontal bean span though.

 

[LD1]

The tables you see may only be applicable to a complete component design of the company issuing them. Any deviation from that design negates their use.

Maybe?

But the tables from harrington and CM, apply to MY situation. Using "their" end trucks or "mine" dont change the span, dont change how the beam attaches to the truck, and dont magically change the properties of the steel. Therefore, if a W18x60 bean is good to span 40' and carry 2k sitting on their trucks and columns, its good enough for me.

 

[MichiganIron]

Lateral torsional buckling is a type of Euler Buckling, at least in the terms we use. The top flange of a beam is in compression, so buckling is usually the controlling design requirement when the span exceeds the depth of the member, in feet. In other words, if the span is 12', it can control for beams under 12" deep.

This is a very serious consideration. Most beam tables are based on a continously braced top flange. You need to be careful to do the proper conversion for unbraced length. Most structural failures are casued by insufficient connection design, second on the list is buckling.

 

[LD1]

Most beam tables are based on a continously braced top flange. You need to be careful to do the proper conversion for unbraced length.

I really wish I knew why everyone keeps repeating this.

Please show me in any of the following tables, where it says its based on a braced top flange?

http://www.harringtonhoists.com/tech_support/edocs/EDOC 0367 rev02.pdf
Adjustable Height Steel Gantry Cranes, Gantry, Gantry Crane
http://www.gaffey.com/descriptions/productspecs/BridgeKit_Man.pdf
http://www.washingtoncrane.com/PDFs/Spanco_gantry_cranes_brochure_2015.pdf
http://www.onecranesource.com/pdf/hoists/crane-bridge-thru.pdf
http://store.americancrane.com/Asset/Crane-Comp-Drawings-and-Spec-CSL-1002-0407-opt.pdf

Sure, some of them have a "*" or specify "w/ CX x XX channel cap. But alot do not. The ones that do not.....WHY do you keep saying they assume it is braced when it IS NOT.


Harrington says I can span 40' with a single unbraced w18x60 and lift 2-ton
Washington crane calls for a W18x55 for a 35' span good to 2-ton unbraced
Goodwin also calls for w18x55 for 35' and 2-ton
CM calls out a w14x53 for 36' and 2-ton
Cranesource calls for a W14x61 being good for both 36' and 38' with 2-ton

So you care to tell me why I cannot rate my W18x60 spanning 37' good for at least 2-ton and not have to worry about buckling?

 

[LD1]

Most beam tables are based on a continously braced top flange. You need to be careful to do the proper conversion for unbraced length.

I really wish I knew why everyone keeps repeating this.

Please show me in any of the following tables, where it says its based on a braced top flange?

http://www.harringtonhoists.com/tech_support/edocs/EDOC 0367 rev02.pdf
Adjustable Height Steel Gantry Cranes, Gantry, Gantry Crane
http://www.gaffey.com/descriptions/productspecs/BridgeKit_Man.pdf
http://www.washingtoncrane.com/PDFs/Spanco_gantry_cranes_brochure_2015.pdf
http://www.onecranesource.com/pdf/hoists/crane-bridge-thru.pdf
http://store.americancrane.com/Asset/Crane-Comp-Drawings-and-Spec-CSL-1002-0407-opt.pdf

Sure, some of them have a "*" or specify "w/ CX x XX channel cap. But alot do not. The ones that do not.....WHY do you keep saying they assume it is braced when it IS NOT.


Harrington says I can span 40' with a single unbraced w18x60 and lift 2-ton
Washington crane calls for a W18x55 for a 35' span good to 2-ton unbraced
Goodwin also calls for w18x55 for 35' and 2-ton
CM calls out a w14x53 for 36' and 2-ton
Cranesource calls for a W14x61 being good for both 36' and 38' with 2-ton

So you care to tell me why I cannot rate my W18x60 spanning 37' good for at least 2-ton and not have to worry about buckling?

 

[bigdeano]

You're going to have to get a roof rack for your car to carry a beam that long :laughing:

 

[Streetcar]

I really wish I knew why everyone keeps repeating this.

Please show me in any of the following tables, where it says its based on a braced top flange?

http://www.harringtonhoists.com/tech_support/edocs/EDOC 0367 rev02.pdf
Adjustable Height Steel Gantry Cranes, Gantry, Gantry Crane
http://www.gaffey.com/descriptions/productspecs/BridgeKit_Man.pdf
http://www.washingtoncrane.com/PDFs/Spanco_gantry_cranes_brochure_2015.pdf
http://www.onecranesource.com/pdf/hoists/crane-bridge-thru.pdf
http://store.americancrane.com/Asset/Crane-Comp-Drawings-and-Spec-CSL-1002-0407-opt.pdf

Sure, some of them have a "*" or specify "w/ CX x XX channel cap. But alot do not. The ones that do not.....WHY do you keep saying they assume it is braced when it IS NOT.


Harrington says I can span 40' with a single unbraced w18x60 and lift 2-ton
Washington crane calls for a W18x55 for a 35' span good to 2-ton unbraced
Goodwin also calls for w18x55 for 35' and 2-ton
CM calls out a w14x53 for 36' and 2-ton
Cranesource calls for a W14x61 being good for both 36' and 38' with 2-ton

So you care to tell me why I cannot rate my W18x60 spanning 37' good for at least 2-ton and not have to worry about buckling?

LD
You seem to be pulling ratings from different tables. At times you list stress and other times you give a beam size for a specific span. The stress from beam tables assumes a restrained flange and does not account for dynamic loading . If you use the beam stress you can have failure from loading not checked
The crane tables will be checked for various failure methods and will produce acceptable results

 

[LD1]

LD
You seem to be pulling ratings from different tables. At times you list stress and other times you give a beam size for a specific span. The stress from beam tables assumes a restrained flange and does not account for dynamic loading . If you use the beam stress you can have failure from loading not checked
The crane tables will be checked for various failure methods and will produce acceptable results

Have no idea what tables you guys keep referring to? the ONLY tables I have ever referenced are the ones specific to bridge crane design, which are unrestrained UNLESS OTHERWISE NOTED.

Any other calculation for stress, deflection, etc has NOT been from a table. They were calculated from the formulas.

We can debate all you want, but its a moot point. I have a W18x60 beam. (well actually a 25' and 12' beam that are being welded together). It is going up and will lift whatever I need. I will have no hesitation at all if I need to lift 5k

 

[Jim Timber]

First post was 5 ton, now you're down to 2 ton.

Lots of arguing and we've never seen a print of what you intend to do.

Good luck man. I'm not sure what you're arguing anymore.

 

[CDN Farm Boy]

Can someone clarify a couple of terms for me? It would seem that braced top flange = restrained top flange and unbraced = unrestrained buy what does that look like in the real world? I think someone mentioned welding a C channel to the top flange, essentially making it into a box. Is that what is meant?

I'm a carpenter, my idea of bracing is a whole lot different than what seems applicable in this situation.

 

[LD1]

First post was 5 ton, now you're down to 2 ton.

Lots of arguing and we've never seen a print of what you intend to do.

Good luck man. I'm not sure what you're arguing anymore.

I have re-evaluated my needs. Making one to lift 5-tons wasnt going to be as feasible as I wanted. So I decided to start looking into something in the 4k-6k range, and scored a good deal on some beams that can handle that. If I ever do need to lift more, I can use a temporary jack post or just make sure I lift near one end. But doubt I would ever need to lift more.

It seems the arguing is coming from people/engineers that are saying and assuming things that I NEVER said. Constant references to "charts" and requirements of top flange bracing. Where the ONLY charts I have ever mentioned are ones specifically for bridge crane design and DO NOT require bracing. So when I say something like "I am not concerned with LTB", doesnt mean that I am ignoring it as a factor in design. It just means that the beam is stout enough for the load rating/span that LTB is not going to happen. (according to all the crane mfg's charts.)

SO I guess what I am arguing is why people keep bringing up LTB and falsely saying that "charts assume braced top flange"? Honestly I thought I was done with this thread. I have my beams and my design planned out in my head. I have no more questions about design and calculations.

I dont have any prints But can describe the design..

There will be 4 columns. Made from W10x33 beam with a 12" x 1/2" thick square plate welded on bottom anchored to the floor. These columns will be right about 10' high.

On top of those will sit W8x35 beams that are 15' long. So they will overhang the columns 1-1/2' on each side.
On top of those will be the 15' of 40# rail. The end trucks will have 8" wheels on 4' centers and made from 6x6x1/4 HSS

On top of the end trucks will sit the 38' long beam W18x60 beam. (effective span of 37')

Can someone clarify a couple of terms for me? It would seem that braced top flange = restrained top flange and unbraced = unrestrained buy what does that look like in the real world? I think someone mentioned welding a C channel to the top flange, essentially making it into a box. Is that what is meant?

I'm a carpenter, my idea of bracing is a whole lot different than what seems applicable in this situation.

There are many ways to brace the top flange in the real world. If using multiple I-beams like making a floor or bridge, you can use x braces like you do with the floor joists on a house. Like this Bracing systems - Steelconstruction.info

For single beams like I am doing, if it is required, you can use a channel cap. Like this How to strengthen I beam deflection - Structural engineering other technical topics - Eng-Tips

 

[Egon]

Even the welds have to meet certain standards for design consideration.

 

[Streetcar]

Egon
Comment on support was attempt at humor.
Welds are important in tension areas under repeated loading. That is assuming it is of good general quality.
For home use ,the welds should not be a problem

 

[Streetcar]

duplicate

 

[LD1]

Started a new thread with some pictures of the build
http://www.tractorbynet.com/forums/build-yourself/348347-building-my-bridge-crane.html#post4296425