camber for steel i-beam as per US Code

[Jason8zhu]

Hi all,
the following is a US code requirement for camber:

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1.2.10 CAMBER (1995) R(2014)
The camber of plate girders more than 90 feet in length shall be equal to the deflection produced by the dead load only. Plate girders 90 feet or less in length and rolled beams need not be cambered.
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now my I-beam is 30 metre with deflection by dead load of 6 mm.

Two questions for help:
1～for this CODE requirement only, if i fabricate the beam with camber of 6mm then , when the inspector inspect it，he will find a camber of zero. so does it mean i need to fabricate camber of 6+6 is 12mm?

2～ if the client ' s drawing shows a camber of 15mm, does it mean i need to fabricate a camber of 6+15mm?


All advice are welcome. Thanks in advance.

 

[Ron]

Hopefully the inspector will know what he/she is doing and will measure the girder in a vertical position, supported as designed, and measure the deflection at the points specified in the documents. If 6mm of camber is specified for DL of the girder only then the deflection measurement will be zero if cambered properly. Make sure the camber specification is clear in what is considered DL. Does it include tributary dead load?

 

[dhengr]

Jason8zhu:
As Ron suggests, the DL could involve the DL of the roof, floor, ship deck, permanent mechanical equipment on the beam, etc. etc., but not various live loads. Also, 6mm (.25") of deflection or camber in a 98' long beam will be within the mill or fabricating tolerances, it is a pretty small number. Also, how is this beam supported and in how many locations, can you even transport that long a beam? Can you make that much camber up in the connections, in the beam bearing elevations, etc? What sort of a structure is it in, who’s code is that? You have to iron all this stuff out with your client or the code authority, only they know why they called that requirement out, and what loads apply. You can accidentally fabricate/weld that much camber into a plate girder (fabricated beam), and you have to guard against this or design, fixture and sequence welds to control this distortion. Most fabricators start out their fab. process on rolled beams by putting the mill camber up. And, to actually have to go to some effort to put a .25" camber in a beam would be quite expensive for that little camber.