Welded crane rails
Welded crane rails
(OP)
I have simple supported crane beams over which sqaure rails need to be welded. Welding rail over the top flange will induce continuity on other wise simple supported beams. How to take care of this induced continuity ? or is it ok to provide rail joints at each ends of the crane beam ? any reference will be apprecaited






RE: Welded crane rails
RE: Welded crane rails
RE: Welded crane rails
1) ability to adjust alignment in service
2) no elastomeric strip under crane rail
3) possible serviceability issues arising from increased number of rail splices
Out of curiosity, what is the crane size and frequency of use that will be operating on the runway?
RE: Welded crane rails
RE: Welded crane rails
1. Welding = Trouble
2. Bolts in tension = Trouble
3. Fully tensioned bolts in shear = Better
Of course it is all in the detail. Welding of components to the girder is fine so long as you can accurately determine the stress at the weld and calculate the expected fatigue damage over the life of the structure.
Have you seen this thread yet? http://www.eng-tips.com/viewthread.cfm?qid=309620
It seems as though your situation has been dealt with before. The last post mentions this being completed successfully on a runway 100 feet long.
RE: Welded crane rails
My specific concern is the continuity of rails over simply supported runways and the resulting induced continuity. This is applicable not only to welded rails but also to 'fixed' rails on top of runways ...hence is a common problem and must have been dealt before. need to know how to take care of this situation
Thanks
RE: Welded crane rails
The continuity force in the rail will vary about linearly with the depth of the beam. You'd need to add a lot of depth to seriously reduce the continuity force in the rail.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Welded crane rails
RE: Welded crane rails
Will the bottom flange bolts shear off due to continuity forces in the compression flange? Could that connection be designed to allow axial slip on one side of the connection? If you could do that reliably, it might relieve the continuity as well.
I'm interested to see what comes of this too. As you've mentioned, it must be a fairly common issue.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Welded crane rails
I agree with most of your assessment. My understanding is that it is not just the section depth that will make the contribution, but rather the stiffness of the section as a whole (i.e. thicker flange beam will carry more moment and hence reduce axial load in rail). Welding the top rail to the runway girder forms a combined section which will see shear flow between the weld connecting the rail to the girder. The axial force in the rail is influence by more then just the distance between centroids (that is, combined moment of inertia should be computed as there will be a stress gradient in the rail since stress = M*y/I). I think the point you were trying to make here is that despite whether the rail has a joint at the end of each span, there will still be considerable axial compression in the rail.
@SHS456
I have seen runway girders which have slotted ends at one end of the bottom flange to facilitate thermal growth and promote rotation. Such details usually call for snug or hand tight bolts with lock nuts. I did a very rough model of three spans with girder moment released and rail continuous. I found considerable compression to exist at mid span of the rail as expected, but the axial tension in the rail transferred beyond the supports seemed quite manageable. I have attached screenshot showing load location and resulting axial load in the girder and rail. If you are getting very high axial tension at the supports it might be worth checking the end releases of your girders to ensure they are acting as pinned joints (I made that mistake this morning in my haste).
Its an interesting topic - looking forward to hearing your findings.
RE: Welded crane rails
I agree that, until welds break, the beam and rail will form a composite section everywhere other than the joint. This will see the rail in compression at mid span and create a shear flow demand in the welds.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.