monorail design loads

huangyhg

monorail design loads
i will be reviewing some exisitng monorails and also designing some new ones in the coming months.  i was wondering if anyone has advice or could suggest a reference that addresses impact loads.  in particular i am curious about what horizontal loads should be considered.  aisc talks about a 20% load for crane runway horizontal forces, but doesn't this just apply to larger bridge cranes, which can move in two directions, and not single beam monorails?  asce-7, section 4.10, seems to address vertical impact quite well.  however, when discussing lateral forces they only refer to crane runway beams with electrically powered trolleys.  does this mean that by code i am not required to apply lateral loads to a monorail beam?  i think that it is prudent to include some load to allow for some movement of the lifted load, but the 20% seems large.  any thoughts would be apprecitated.  thank you.
in the us the main documents you would design to are asme b30.11 "monorail and underhung cranes" and cmaa(crane manufacturer's association of america) 74 "top running and under running single girder electric traveling cranes utilizing under running trolley hoists"
the 20% side load from aisc is for bridge cranes to take into effect the loads on the runway girders when the trolley is traversing and suddenly stops.  this does not apply to a monorail.  the main horizontal load on your monorail comes from picking up a load that is not directly under the crane.  it is a common practice to assume the loads are taken at 5 degrees out of plane and check for torsion and horizontal bending but i can't find the reference for that.
since asme b30.11 is a safety code it is pretty general but it does offer some things to consider.  cmaa 74 gives all the load factors to consider including:
dead load factor  1.1 - 1.2 depending on hoist travel speed
hoist load factor  .15 - 0.5 depending on hoisting speed
inertial drive forces
test loads
cmaa 74 also gives all the allowable stresses and load combinations.
don't forget to check the flange bending under the concentrated wheel loads.  cmaa 74 gives some emperical formulas for this but in the past there have been some errors in their formulas.  i like to do a second check of the flange stresses going back to basics.  a good method for second checking your answers on the flange stresses is given in the modern steel construction (aisc magazine) dec 1999 in the steel interchange by david t. ricker.  the problem becomes more complicated with tapered flanges.
good luck
in addition to the 2 standards mentioned above, you should also refer to the american national standard ansi mh27.1, "specifications for patented track underhung cranes and monorail systems".  this standard (referenced by the asme b30.11) is published by the monorail manufacturers association, inc., an affiliate of the material handling industry (mhia) out of charlotte, nc. their website can be found at
some how, in my recent job changes, i lost my design notebook i had set up on monorails.  however, i have always used the 20% lateral load and a 10% vertical load impact factor on the monorails.  the mhia as listed above, if i remember right, limits your tensile stress in the flanges of the beam to 20%, and is extremely strict on the deflection criteria.  i don't re  
seaoc had a lengty discussion about this topic in their newsgroups. try