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Re: Gantry Crane Rail Blockout

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Paul,
 
        I have assessed, reviewed, and/or designed a few gantry cranes over the years.  Following are a few thoughts that may (or may not) be helpful.  You are welcome to the helpful ones.
 
        Your first considerations are probably the load rating and type of wheels you want to use.  Some gantry cranes I have been involved with have been on castors, hence, they could be moved anywhere in the building even when they were loaded.  No rails required!  These have included cranes up to two ton rating.
 
        For intermediate cranes (say three ton to seven or possibly ten ton) you could consider using solid rubber wheels which do not require a rail but probably do require a dedicated runway location in order to have adequate foundation to avoid cracking the slab.
 
        For larger design loading, say above seven or ten ton, you will probably opt for a rail system.  Whether you use a block-out or not is another question.  this, of course brings up the question "do you use a solid bar for a rail or do you go to an actual ASCE rail?"  This will affect what type of block-out, if any, you design.
 
        You haven't indicated why you need a block-out.  I'm speculating that you want to avoid a tripping hazard or provide some type of cross rail access for a vehicle or a dolly or some other wheeled transporter.  If you can use the solid bar rail you can probably use a channel cast into the floor toes up (either a C or an MC shape) according to the depth you require.  I'm sorry; I don't have a detail for a larger cast crane block-out.
 
        Hope this is helpful.
 
Regards,
 
H. Daryl Richardson
----- Original Message -----
To: seaint
Sent: Wednesday, April 18, 2007 4:56 PM
Subject: Gantry Crane Rail Blockout

I've got a client that wants to incorporate a 'future' 20 ton gantry crane into their manufacturing facility.  I was envisioning a block out in the slab on ground that is removed and the rail set in the block out, leveled, plumbed and polyurethane fill cast around the rail to set it in place.  This detail is used locally as part of the light rail commuter transit system.
 
Others in my office are voting for an embedded plate in the bottom of the block out with the rail ultimately welded to the embed plate.  My concern with this approach is alignment and elevation tolerance.  I know from experience that embedded plates don't get the same close tolerances that a rail support needs.  Also, with the future installation of the rail and crane, the General Contractor may not meet the strict tolerances for the rail and the owner might suffer later during rail installation.
 
As another alternative I was thinking that I could use rail clamps and concrete anchors and shim to the proper elevation.  I'm looking for your input and alternatives. 
 
Additionally, does anyone ever provide drainage in the annulus next to the rail.  This gantry crane travels from outside the building into the building.
 
Your thoughts are appreciated.
 
Paul.