You have to first analyse the loads on the beam itself to make sure the beam size can take the loads, then you have to analyse the bottom flanges of the beam to make sure they don't bend excessively as the wheels travel.

I agree with csalvian post but that are some other issues that I think we must consider for this kind of loading case. This kind of questions ocurred me sometimes when designing crane girders and if I have time I i'll try to make a summary, but I would like very much to hear from you speacially about this two ones:

 1- In the case of a welded I profile, usualy the weld is a fillet weld, with no pernetration, thus we can't count with the tensile stress along an axis perpendicular to the weld line. And this really happens in this loadind case.

 2- Should we consider the slope of the bent flange and limit it to a maximum value? I guess that it is analoge to the alowable max relative deflection of the beam(1/600 in most cases) due to the resistance imposed to the movement of the crane car.


 Any further discussion on this subject will be very apreciated.

    Thanks and sorry for my bad english, I'm Brazilian.



    Best

        Fred

For monorails there is a design procedure used by the Crane Manufacturer's Association (CMAA) and defines a procedure that covers the concentrated wheel loads for underslung cranes (both S (tapered flange shapes) and W (parallel flange shapes) are covered).  This gives a combined stress level at the concentrated load and is  an ASD procedure.  This document is about 20 pages.  In addition to this analysis, one must also do an overall beam bending analysis and a deflection analysis.  

Another method which has been around for many years is a set of tables by a crane manufacturer called Wright for again underslung cranes.  This is an excellent starting point.  Given the load and span, the beam (A36) can be chosen in less than 5 minutes (one minute more likely) (deflection, overall bending, and concentrated stresses are considered).  S, W, C+S built-up, and C+W built-up shapes are included.

Cantilevers should not exceed 25% of the maximum simple span.  Curves should be analysed using a FE analysis.

JRM,

  Could you please tell where can I find this tables (Wright).



    TIA

      Fred

Fred,
I don't know where you can get them (Wright tables), but I could scan the tables that I have.  But how would I post them?

  jmark,

  Would you please email me at fkdconsult@hotmail.com, I tryed to find them over the net but get it.


  TIA

    Fred

The British Standard BS 2853:1957 covers the design of steel overhead runway beams. It uses an allowable stress design approach. Although more than forty years old, the code is still applicable in the UK.
The method limits the transverse bending stress in the bottom flange due to load from the hoist. The are various variables that are required such as the number of wheels on the trolley and the set-in of the wheels on the flange. Rolled sections and plate girders can be analysed.    

I have 33 years of experience of monorail beam design,
or as you asked for it, bottom flange loading desig.
Contact me via e-mail (ehcet@idirect.com) or by phone
905-712-2373
Regard Ernie