Expansion Joint in Bridge Crane Runway

[vandede427]

I'm designing some new framing to go in an existing building to support a bridge crane. The building is 500'x400' broken into 4 quarters by expansion joints; typical warehouse/manufacturing (tilt-up walls, bar joist, joist girder).

The new crane runway will cross an expansion joint. I've designed the crane beams/columns on either side of the joint to act independently; specifically in relation to transverse and longitudinal crane loads.

The crane manufacturer is hesitent to put a joint in the rail. If the rail did not have a joint, what types of issue would arise with it being the only structure to be linked across the expansion joint. Should the crane beams have the typical 1" gap similar to the roof structure, or should it be a flush joint so that the rail isn't spanning the 1" gap?

I know my fair share about designing crane supports but I must not understand this particular concept of why the rail should be completely continuous.

 

[Teguci]

I'm leaning towards the "don't have a joint in the rail" position too. Longitudinally the rail should float across the expansion joint. Transverse and vertical the crane rail shouldn't have any sudden changes.

The expansion joint should allow for longitudinal movement only. The vertical and transverse directions should be locked out with keepers.

 

[vandede427]

Misallignment is the biggest reason I can think of. The last thing you want is the crane wheels jumping off the rail.

 

[paddingtongreen]

I would make the framing independent of the existing structure and continuous. Any discontinuity in the rail, means that the wheels have to go up hill to get out of the joint. You would probably have a higher longitudinal impact load too (think driving over a pothole), unless you figure them to slam the crane against the bumpers to true it up, but that's a different story.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[vandede427]

One line of columns is new, one is existing so the double structure at the joint is already there and the crane is tied into the building.

 

[paddingtongreen]

Okay, a different question, is there a significant variation of ambient temperature in the building? do you need the full gap? it is often only active during construction.

Another thought; could you longitudinally anchor the girder in just one section and use Teflon bearings and guides in the other sections?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[ToadJones]

So you installing an entirely new runway support structure within the confines of an existing building with concrete tilt up walls?

 

[CTW]

Misalignment will certainly be a problem. Also, with a large gap, the potential problems are rail chipping, damage to crane wheels, increased impact, and increased girder stress due to impact.

The third page of the attached PDF should help with regard to expansion.

 

[hokie66]

I would avoid a joint in the rail at all costs. If the runway is anchored near the centre, thermal movement will occur from each end toward the centre.

 

[apsix]

If a rail expansion joint is really required it should not be a 90 degree butt type joint.
I've seen 2 different detail:
1. Joint at a 30 deg angle to the rail, with the gap appropriate for the installation temperature and extreme operating temperatures.
2. Using a halved joint, where the end of each rail segment is sliced down the centreline and then overlapped, and the end gap being staggered. This only works if the rail is large enough.

 

[vandede427]

From my first post, the building is quartered into 200'x250' sections. The new runway runs the full distance of one quarter (200') but only one column bay into the other quarter (40').

If the runway were 200' on one side and 200' on the other, I can see needing the joint and using the joint type aspix decsribed.

I don't think I'm going to put a joint in the rail or the support beams. Even if there is a little connectivity across the expansion joint at the crane beam level (elev+20') the existing roof still has it's ability to be seperate at the +30' elevation.

Thanks guys for your help.