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Participant

Join Date: Jun 2006
Posts: 2

02/11/2007 9:07 AM

I am engaged in design of overhead cranes. I understand that oval cross sectional design of girders are more cost effective than the conventional square section or I section girders. Would anyone be kind enough to enlighten me as to where I can find literature/ books to get into the calculation details?

Pathfinder Tags: design girders overhead cranes
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Anonymous Poster
#1

02/11/2007 6:16 PM

It is a case of sigma = my(bar)/I where sigma is stress, m is bending moment, y(bar) is largest distance from y axis (to top of web for symmetrical CSA) and I is the second moment of area.

The bending moment can be derived but there are a lot of empirical formulas in books like the steel designers manual (Amazon.co.uk will have this) or ASD (American Steel Design) no way near as good but if you have to use those codes then you may be stuck with it and web sites like efunda also search Google there are many web sits offering XL files for such a task. The gantry beam should be a simply supported beam, highest bending moment occurs when the load is in the centre that is why you can reduce CSA as you get closer so the supported ends.

Oval girders are usually plate type girders (fabricated from plates) I do not know of any complete rolled section ones (doesn't mean they don't exist). You use a plate girder when you cannot find a rolled one big enough or you have a special case design such as weight reduction. U.B. are made up to 914mm high

So if you can use a rolled section be UB, UC, W and they do make a section with a wider top flange that is quite commonly use in rolling gantries.

Call a large steel supplier, in the UK SPS and Browne McFarlane will supply a very good pocket book that has all the section sizes and mechanical and section properties, in the US the suppliers I use have nothing like it for the US sizes of section.

You have to determine your capacities, SWL's, dynamic forces, working span, before you can determine what the best type of beam design to use is.

Just persevere with the internet and most things you need you will be able to find.

Make sure you load test it properly before using it in the work place. Standard lifting equipment has a SF of 5 (i.e 5x rated SWL)standard load test is 110% SWL for a crane you would have to check gantry type, all slings and shackles should be tested to 200% SWL

The US Navy provide a very good crane guide for free, it covers all crane types it is call P307 and can be found on the NAVFAC website I recommend this.

Oval girders are usually plate type girders (fabricated from plates) I do not know of any complete rolled section ones (dosen't mean they don't exist). You use a plate girder when you cannot find a rolled one big enough or you have a special case desing such as weight reduction. U.B. are made up to 914mm high

So if you can use a rolled section be UB, UC, W and they do make a section with a wider top flange that is quite commonly use in rolling gantries.

Call a large steel supplier, in the UK SPS and Browne McFarlane will supply a very good pocket book that has all the section sizes and mechanical and section properties, in the US the suppliers I use have nothing like it for the US sizes of section.

You have to determine your capacities, SWL's, dynamic forces, working span, before you can deterine what is the best type of beam design to use.

Just persavere with the internet and most things you need you will be able to find

Anonymous Poster
#2

02/12/2007 12:33 AM

the cranes at my workplace are capable of lifting 500 to 750 tons not metric tons, 500 to 750 US Tons. They roll all the way down the bay on big I beam design girders. The I- Beam Girder is probably 8 ft. tall with a lot of I beams welded in perpendicular to it. This Girder is supported by roughly 16" X 16" I-Beams from the ground up spaced probably 20ft. apart. He is right, the US Navy does have good information on cranes. The name on the crane says "Whiting", Hope this helps

Anonymous Poster
#4

02/12/2007 7:02 AM

Here is the the link for the P307, the US Navy and Army Core of Engineers is a very good source for free information, on design codes.

The below is also very good for the basic mechanical engineering principles

Participant

Join Date: Jun 2006
Posts: 2
#9

02/13/2007 9:41 PM

Dear Guest

Your comments are most helpful.Many thanks. I would like to pick up some of the reference books/papers you suggest. Can you tell me how do I go about it? I am stationed at Delhi.

As regards elliptical section girders, I compared the bending moments of both elliptical and rectangular girders of same cross section. There is saving in metal, but not very significant. On the other hand, oval sections stand torsional stresses better.

Such sections may find an edge for the telescopic boom of a mobile crane. The inner section can be steadied better inside the outer section. Nylon may be used as an antifriction material between the two sections.This is just a thought.

Regards.

Anonymous Poster
#10

02/18/2007 7:47 AM

I am not entirely certain on what you are comparing the torsional stress too in either case or where you would have a high enough loading to be concerned. I would suggest resistance to local web buckling would be better in the tapered profile girder (that is what I assume you mean be oval, you should have a flat top section in order to run your hoist dolly along, unless you are underslinging with a single beam and joist dolly) than a standard I beam, this is only becuse of the reduction in the critical height, if the beams maximum heights are the same. A closed rectangular section would be better again. Stiffener plates can be welded between the top and bottom webs of I's to prevent local bucking. But you really need to crunch some numbers with the properties of your sections and loads, to determine this.

Most of the information you need you can find on the internet if you have problems purchasing texts. It will take a long time and you should compare many documents, sites, or texts to ensure you are heading in the right direction. Manufactures will not be very helpful in free design help, that is not their game. Have you tried a university or college library, it may be free to browse or you may have to pay to join if you are not a member of the institution, but they are a good sourse of such text books, and if not you may find help there as to where to buy them, just be careful not to get a "ragging".

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#3

02/12/2007 4:51 AM

Isambard Kingdom Brunel's design for the Tamar Bridge at Saltash may prove enlightening.

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#5

02/12/2007 8:49 AM

Girder design and gantry design are parts of the problem. Are you going to do the control system design also?

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Participant

Join Date: Jan 2007
Location: Utah
Posts: 1
#6

02/12/2007 10:04 AM

Crane Manufacturers of America, CMAA Specification #70 is the spec I use to design, specify, modify, and maintain cranes used to move Space Flight Hardware for Space Shuttle RSRM Program.

The contact info on the specification is as below:

The Material Handling Institute, Inc.

8720 Red Oak Blvd. Suite 120

Charlotte, NC 28217

704/522-86644

Good Luck.

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#7

02/12/2007 10:18 AM

Check out http://www.nelsoninc.com/TRSG.htm They have crane kits too!

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#8

02/13/2007 9:55 AM

go to mdsolids.com and they have a program you can use after registering...