Crane Runway Beam Design

[cmbyrd77]

In ASCE-05 it states that the lateral and longitudinal forces shall act at the "traction surface" of the beam. What exactly defines the "traction surface?" I have two wheels on each side of the bridge beam. The wheels are spaced approximately 54" apart. The max. wheel load is 4,843 lbs. So do I also apply the lateral and longitudinal forces right at the wheels, therefore have two loads that are approximately 54" apart, or do those forces only get applied in one location. Thank you in advance for your help. This is my first crane runway beam design.

 

[ToadJones]

you need to look at AISC Design Guide 7 for industrial buildings or AIST tech report 13 for hevy mill construction.

There are vertical wheel loads, longitudinal tractive forces, and side thrust forces.
The traction surface is between the wheel and the rail which is several inches higher than the top of the top flange.
This creates a larger moment arm for torsion on the girder as well as tractive strong axis moments (if you care to get into that much detail).
You should apply the wheel loads at the proper spacing and at the tractive surface. For a simple 4 wheel crane (2 wheels per runway girder) the Table 3-23 in the Black Book will give you simple formulas for max smoment and shears for moving loads on simple span beams.

 

[cmbyrd77]

Yeah, I agree with everything you just said, but what I'm trying to figure out is if the lateral thrust force and the longitudinal forces are also applied a the same locations of the wheels, or in between, or another locations. I realize that they occur at the top rail in cross section. I am thinking more in plan view. Thank you for you help.

 

[ToadJones]

apply them where the wheels are.
You have a short wheel spacing so the moments and shears will be close to what you get for a point load but not exact.
Again, look at DG 7

 

[cmbyrd77]

Thank you very much. Yeah, I've been looking at DG 7, but it didn't really cover that question. I'm also trying to figure out how to avoid checking torsion in the wide flange if I don't use a channel cap. Any thoughts on that? I plan on detaling it so I have some sort of bracing of the top flange at least at the columns.

 

[ToadJones]

AIST TEch Report 13 has a method for increasing the lateral forces in place of designing for torsion.
I believe DG 7 uses only the top flange properties for lateral forces as a way to avoid checking for torsion.