Drift limits for a mill building
Drift limits for a mill building
(OP)
I have a contractor that is bidding on a design/build for a new mill. One of the buildings is a mill building that will house an 80 ton class F crane. This thing is 82 ft high and 76' wide and they want the frames on 30 ft centers.
Anybody have a feel for what drift should be allowed due to wind/seismic. H/400 is less than 3 inches and I'm having a hard time making that happen.
tw
Anybody have a feel for what drift should be allowed due to wind/seismic. H/400 is less than 3 inches and I'm having a hard time making that happen.
tw






RE: Drift limits for a mill building
Wind seismic and bracing are other issues that should clearly be stipulated in the package... as well as warranty beyond the one year... I use a fairly restrictive set of notes for metal buildings... comes from a problem with girts supporting the top of a masonry wall having an L/90 deflection... and the extra to contract for correcting this to something reasonable...
If it's an industrial building, you may want to spec additional loading for the frame and purlins (for example 1000 lbs supported from any point on a purlin or 2000 lbs supported from any two locations on the frame). Check with the owner to see what his needs are and have him sign off the loading...
Just some ramblings...
Dik
RE: Drift limits for a mill building
Lateral Stiffness for Industrial Buildings with Cranes
Drift criteria for buildings with cranes are not only dependent upon the choice of wall system, but also upon crane movements. For pendent-operated type crane systems, buildings with calculated wind drift ratios of H/100 have performed. However, crane movement can generally be observed. A structure which is this flexible should be described to the owner beforehand so he is not surprised to see his structure move and rattle when the crane is in use. It is suggested, for cab-operated cranes, that building lateral drift be limited to H/240 for both crane loads and wind loads.
In addition, the lateral sway at the elevation of the crane runway should be limited to roughly one inch. Structures supporting computer-controlled cranes will probably require more restrictive tolerances. Although not a drift criteria, it should be mentioned here that it is not recommended to tie masonry walls into crane column steel because of the frequent movement of the columns due to crane action.
RE: Drift limits for a mill building