Monorail beam size

[albresco]

Does anyone know of a chart available on line for acceptable sizes of crane rails to be used with hoist trolleys. Specifically, I am looking for an acceptable beam to be used for a 10 ton hoist. I have sized the beam but am being questioned about the bending resistance of the bottom flange. The span is 9 feet with a 4 foot cantilever.
Alternately, does anyone have a formula that would calculate the strength of the bottom flange in this situation?

 

[irishengineer]

Dear Albresco,

I am not aware of any online chart per se but there are
two publications which you might consult. One is Roark's
Stress & Strain. It has information concerning this type
of calculation. The other is the CMAA publication no. 74
for single girder cranes. There is some information
concerning local flange bending in crane girders. These
are manual methods and I think preferable to some generic
chart. The size of an acceptable beam is a function of
the wheel load, position of the load relative to the edge
of the beam, support spacing, etc and these need to be factored into your selection and a chart may not detail what assumptions were made in its development. This could lead to a catastrophic failure. I am not trying to discourage you from using existing results, but rather pointing out the value in knowing where they came from. I work for an industrial crane manufacturer and we have pre-calculated girders, but they only apply to our trolley designs. If another manufacturers trolley is used and the wheel geometry is different, the girder may not react the same even though the capacity of the trolleys is the same.

I hope this is of some help to you.

Good luck,

Irishengineer

 

[austim]

albresco,

It could be worth your while visiting

http://www.standards.com.au.

The Australian Crane Code AS1418 has a small appendix dealing with the design of monorail beams, including assessment of the minimum acceptable flange and web thicknesses.

My own copy of the code is fairly ancient, and has now been superseded, but you should find the problem covered in AS 1418 Part 1, "General Requirements"

PDF copies of all Aus Standards are downloadable at slightly less than the full hard-copy cost. A downloaded PDF of AS1418.1-2002 would cost you $A139.39.

 

[albresco]

I now have a copy of the CMAA 74 and the calculations appear straight forward although there is not much theory background.
In the formula 3.4.4.1, there is a factor "Txy" (Tau subxy) for the horizontal shear stress. There is no formula mentioned to obtain this number. Is this simply the shear on the beam or is there another factor I should be using?

Thank you
Doug

 

[irishengineer]

Dear Doug,

The factor "tau sub xy" is the shear stress in the
beam. It can be calculated using ordinary methods. The
other thing I wanted to point out are that the deflection
limits are different for monorail beams than for crane
girders. The limits are given in a publication by the
Monorail Manufacturer's Association. There is a copy in our office and I used it last about a year ago to specify a
beam type for a customer. I am pretty sure the limit was
different than the 1/600 & 1/888 as is given in the CMAA
#74 publication. Your span in this case is the distance
between supports. I will be out of the office this week
but I can at least check for you the limit when I return
or you can go to their website and see if this publication is available in the meantime.

I hope I was able to be helpful.

Sean (Irishengineer)

 

[albresco]

Thank you for your help. If the deflection is different from that stated in CMAA 74 I will need it too. I look forward to your information.
Doug

 

[ehcet]

Hi
The ratio between span and overhang is irrealistic for 10 Ton capacity. Not only the local wheel load but also
the torsion on the unsupported beam will cause problem.
Local stress explained in CMAA specs. Original investigation and finalizing the formula was done in Germany
about 15 years ago. More information can be found in FEM
crane specs, or DIN specs. Be careful.
Some old formula used for 25 years= 1.15*R/4*t square.
Stick with the new regulation, but careful because there are
different method for parallelflange girder or sloped flange girder. Also you must know the trolley manufacturer research
information regarding to the dimension where the load is
transferre to the girder. (i=...)
Contact me if you need more info.
ehcet@idirect.com

Unsupported overhang will be a big problem!!!!!!

 

[irishengineer]

Dear Doug,

As promised I checked the copy of the publication which I
mentioned previously by the Monorail Manufacturer's Assoc.
It is titled "Specifications for Underhung Cranes and
Monorail systems". Our copy is from 1973 and is old.
Refering to section 3.4, the deflection limit listed is
less than 1/450 of the span for spans under 46'-0". For
spans over this length, the deflection is to be limited to
less than 1-1/4" (not including impact). As I mentioned,
the copy we have in the office is old and I am sure a much
more recent version is available. Our main business is
cranes and we don't usually specify monorail beams.
It sounds like ehcet has much more experience in this
area and that he would be a better guide for you on your
problem.
I hope I was of some help to you. That is the purpose
of this forum.


Sean (Irishengineer)

Good luck and thank you for the opportunity to be of
service.

 

[MickKirk]

In Britain we use BS853:1957 to calculate the design of Runway Beams. A Beam the size of U/B762x267 (173kg/m) would be capable of taking the load you require 10,000kg, taking into account the dynamic load of 125% for the electric hoist, and that the hoist trolly would be running at worst on the edge of the lower flange. This also takes in to account the deflection criteria of 1/500 for the Simply Supported span and 1/250 for the Cantilever Span. You should also ensure the supporting structure is capable of taking the reaction load/force at the joint of cantilever, the reaction being 16,971kg. 9ft (2743.20mm)Simply supported span, 4ft (1912.20mm) Cantilever span.

 

[MickKirk]

The British Standard for Design of Runway Beams is BS2853:1957. Beam size for the above criteria you would get away with a U/B 457x191mm (98kg/m) but this very close to failure.