Square Bar Stock for Crane Rail 2

[Everynameistaken]

Hello,

I just received crane shop drawings and the crane supplier has noted a 2"x2" stock for the rail. To us this seems strange as typically we use standard crane rails and to connect to the crane beam we either bolt them, use a flat bar clap that is welded to the crane be a or a gantry clip.

My biggest question is how do I connect this square stock to my top flange, is it simply OK to stitch weld or full length fillet weld? How is this in fatigue?

My next question, how do I splice this rail? usually we use simple space crane beams and at the crane beam joint we make sure the rail spans across the joint and then butts into the next rail, with welded bar stock, the bar joint has to be at the crane beam joint and under deflection we will get a gap??

Any thoughts or past experience would be helpful!

 

[Agent666]

I've seen people specify it as being welded. However this is about the worst thing you can do for fatigue. Also any continuity of the rail where beam is not continuous can be a real issue and point of failure.

I remember watching an AISC webinar quite some time ago which went through this aspect in detail and basically concluded 'don't do it'. I'll try find it again and post back.

 

[Agent666]

This is the webinar I was thinking of. Part on cranes starts at around 3 minutes. The bits that apply to your situation is the importance of allowing the rail to slip longitudinally, which welding essentially restrains. Check the part on diaphragm plates (around 6 minutes) and rail clips (around 23 minutes), but the whole thing is worth a watch.

AISC field fixes webinar

 

[JAE]

This is from an online Q&A for CMAA's specification:

[blue]Q. Does "bar type rail", such as that from standard steel bar stock meet the intent of Section
3.10?
A. CMAA does not specifically address the use of square/rectangular bar for bridge rails.
CMAA does not preclude the use of square/rectangular bar in crane construction by
allowance of other commercially rolled sections. However, design requirements (i.e.
bending strength, wear, wheel loading and wheel contact, etc.) for square/rectangular bar
are not addressed and the acceptability per application is the responsibility of the
manufacturer.[/blue]

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[Everynameistaken]

Thanks everyone,

As I thought, bad idea, with no good way of making it work.

I have asked our coordinating professional to see if they asked for a rail or allowed the square stock. If it is allowed by specification I have asked for the crane supplier to provide their preferred detail (to at least review) and to provide minimum requirements for the rail, hardness for example.

This way at least if there is an issue down the road the crane supplier has told the client what they need!

 

[JAE]

I do believe that some crane manufacturers now have crane "kits" (they call them) and some of the wheels are supposedly designed only to work with the steel bar and not the typical ASCE "T" rails.
You might check with your crane manufacturer to see if this is the case.

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[hokie66]

The square bars are sometimes used for cranes of low capacity. Probably 10 tons or less.

 

[FLCraneBuilder]

I've been wondering when I'd have to weigh in on this one...
1) Europe and most of the rest of the world have been using bar stock for many many years
2) It is far more economical at initial installation - and works fine for moderate service cranes
3) And if properly sized - can work for heavy service as well (not severe duty though)
4) One significant down side is that once welded in place, its costly to replace - so if the application ever sees a potential to replace the rail, I'd shy away from it
5) Bare in mind that the 2 x 2 you mentioned may be replacing 40# asce.. which has an effective head width of only 1-1/4".... This variance offsets the softer bar stock's lower durability
6) our firm uses medium carbon steel as opposed to A-36 or Gr 50
7) We've used it on up to 50 ton Cranes (for trolley rail) when the customer demands we use every trick in the book to get the costs down... (or they quite literally will not buy the crane)
8) Yes - we simply stitch weld it - we vary size & quantity of welds based on lateral forces the rail will see
9) No - we do not weld the bars together where they meet... why?? - ASCE rails are not welded splices - no need to... HOWEVER - under no condition would we put a bar rail splice over the gap in runway beams - makes no sense
10) we have not yet gone the route of considering the bar part of the runway beam section.. but when you add a bar weight of 6# to 12# / ft of rail to a smaller beam - say W12 x 35, it has the potential to contribute to the beams capacity

All of this is going to catch many of you off guard - particularly the more experienced guys... But believe me - there is a strong trend in the crane industry towards this.... On a final note - our firm sells roughly seven thousand feet a year of bar rail... and have been for many years... We know & understand it quite well

 

[JAE]

Good info, FLCraneBuilder. Thanks.

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