conveyor loads

huangyhg

conveyor loads
i am calculating foundation loads for several conveyors and am curious whether i should include seismic forces.  these are for an area that used to be ubc zone 2.  i have been told that no one else does this.  is there a special design spec for conveyors?
thanks,
-mike
typically for bulk material handling conveyors we don't design for seismic loads unless we are in zone 3 or higher.  sometimes in zone 2a.  it usually depends on the customer and the situation.  95% of the time it will not control anyway until you get to the higher zones.  even in the higher zones the customer only wants the structures to meet seismic and the conveyors not.  the justification is that the conveyors are "low risk" to human life and are highly redundant so when designed for wind they will survive most shakes.  also consider the return interval for quake design and the life expectancy of your structure.  a conveyor more than 25 years old in a quarry, although not unheard of, is generally few and far between.
if you do include seismic we usually include dead load and the operational tph material live load.  we do not use the maximum "surcharge" material live load for design.  we do put on the drawings that conveyor designs do not condsider seismic forces and at the discretion of the owner can be included.
aggman,
thanks for the help, you make several good points.  i see now after a few more hours of programming that my seismic forces are about 25% to 30% of the wind forces so the break even point would be about zone 3 roughly.  i do have a conveyor indoors so i'll probably use seismic there for the purpose of checking for minimum stability, but due to the use of standard parts should be better than needed.  using the surcharge ll is probably overly conservative as you indicate.
putting a note on the drawing about seismic design is a nice touch and seems to be the appropriate thing to do.  i would like to do that here but probably won't be able to.
thanks again, it's nice to get a viewpoint from someone else in the business.
-mike
there are some applications where the end use of the conveyor dictates looking at the seismic loading. most coal fired power plants are expected to not only survive a design earthquake, but also to continue to produce electricity immediately afterwards. if the coal handling system went down, the inability to deliver fuel would bring power generation to a screeching halt within hours.