Crane Rail Clip Spacing

[ForrestLowell]

Is there a maximum spacing for crane rail clips? The 1989 version of the AISC ASD manual suggests a spacing of 3', but it is not a hard number. My clips are 9" long and I want to space them 4.5' on center. Strucuturally the crane rail is okay with the lateral loads applied, I am mostly curious if there is an industry rule of thumb or code that limits the spacing of the rail clips. The crane is a large overhead crane that runs on two rails.

Thanks,

Forrest

 

[Harold53]

I think both, 3' and 4.5' are quite high spacing. Please check gantrail.com. You'll find a good bunch of papers to clarify your point.

 

[ForrestLowell]

Thank you for the very useful hint, I looked it up and confirmed your thoughts. To clarify. My clips are not bolted, they are welded to the girder with 18" of 3/4" fillet weld. The 18" of weld goes in and out so that is how you fit 18" of weld on a clip that is 9 inches long. My lateral wheel load is about 100 kips, and the Iy of the crane rail is about 55 in^4. The allowable stress of the crane rail is 80ksi. My critical condition is during a seismic event where the rail is allowed to yield, just not break, so I am allowed to take a 1.6 increase factor to the 0.75*80ksi for an allowable load of 96 ksi. My moment is figured as if it was a point load on a continuous beam, or PL/8.

Thanks again, and let me know if you have any other thoughts. Some other poeple have suggested keeping it to 3 feet or less, but there are considerable savings for my partiular case if I can make few 3/4" welds 18" long. I am mostly worried about the capacity of the rail not the clips.

 

[MJCronin]

have you considered posting on the structual forum ?

 

[ForrestLowell]

MJCronin,

Great minds think alike, I have an identical post on the strucutral board, I was trying to cover all the bases. Seems like most are in agreement that industry practice is to space them closer, but I think we are going to do some in depth analysis and try to space them further apart. So far I haven't learned of anything that will bar me from spacing them further apart.

Forrest