max 10mm deflection between two crane girders when considering skewing forces

[NL4L1F3]

I am trying to design a double girder overhead crane with a span of 40 meters. 2 trolleys are placed on top.

I am calculating the skewing forces for the trolleys using EN15011 or EN1993-3. The skewing forces are as stated below. (see attached image for clarification on how the forces apply to the crane girders)



These skewing forces push the crane girders towards eachother, or away from eachother.

In 1993-6 the following maximum deflection is given between the centre of rails. This is given for the supporting beams of the entire crane, but might also apply for the trolleys, because these have to travel across the rails aswell?



However if i use these tolerances each beam has a maximum allowable deflection of 5mm. With a span of 40m this is a tolerance of L/8000. This seems very strict. My girder requires almost the same moment of inertia around its weak axis as its strong axis. This does not seem right?

The note states that we can increase clearance c. However the skewing angle is limited to 0,015 rad, and this will also increase the skewing forces.

How could i continue? Should the L/8000 deflection limit be applied, or is there a more appropriate tolerance?

 

[canwesteng]

My condolences for having to use EC to design crane runways. I recommend double checking that this isn't referring to a combo of building lateral deflection, beam sweep, and thermal effects. The intent appears to be to prevent skewing or having the wheels rub on the rail, not restrict lateral deflection under crane loads.

 

[HTURKAK]

My points;
- EN 1993-6 is for Crane supporting structures runway beams . The scope excludes the Cranes and a moving parts .
- The limiting values at Table 7.1 and 7.22 is for runway beams nut for crane bridge,
- You are expected to look DIN -EN 13001 OHC bridge design.

​

 

[NL4L1F3]

My points;
- EN 1993-6 is for Crane supporting structures runway beams . The scope excludes the Cranes and a moving parts .
- The limiting values at Table 7.1 and 7.22 is for runway beams nut for crane bridge,
- You are expected to look DIN -EN 13001 OHC bridge design.

​

Yes, that’s correct. However, I haven’t been able to find the maximum deflection in EN 13001. Do you know where these are specified?

That’s why I started looking elsewhere and went by the 1993-6.

 

[HTURKAK]

Yes, that’s correct. However, I haven’t been able to find the maximum deflection in EN 13001. Do you know where these are specified?

I don't have EN 13001 series. (13001-3-1 to 13001-3-1) . But assuming the 10 mm spacing limit for the crane rails defined in EN 1993-6 will be overkill .
In order to get an idea ş looked CMAA specs and found ;
- Max. vertical deflection is 1/600 of span of uncambered girder,
- Max lateral deflection Lr/400 based on 10% of wheel loads.

When you limit both deflections to 1/600 , 40000/600 makes 60 mm.

 

[NL4L1F3]

I don't have EN 13001 series. (13001-3-1 to 13001-3-1) . But assuming the 10 mm spacing limit for the crane rails defined in EN 1993-6 will be overkill .
In order to get an idea ş looked CMAA specs and found ;
- Max. vertical deflection is 1/600 of span of uncambered girder,
- Max lateral deflection Lr/400 based on 10% of wheel loads.

When you limit both deflections to 1/600 , 40000/600 makes 60 mm.

Thank you. I’ve looked into it. However, this means the rails could be spaced up to 120 mm apart. This seems very excessive for the flanged wheels of the trolley?

I have also looked into the australien specifications and here they specify L/600 or 10mm maximum deflection per beam. The maximum spacing between the rails will then become 20mm.

I am also considering to only apply the skewing forces to one trolley instead of 2.