Cambering girders

Date 05-20-2009 16:19

No load is generally taken to be girder laid over with web horizontal. We usually pick up one end a bit to allow stresses to "shake out".
This way, even gravity is not affecting camber - and everyone accept that

As far as vertical position with a laser transit, I peeked at the C 3.5.1.3 commentary. It's pretty lengthy but I'm betting your answer is in there.

By swnorris (****)

Date 05-20-2009 16:25

Same as D1.1...... in the non load condition. AISC refers to it as the unstressed condition..... web horizontal, as Chet said.

By eekpod

Date 05-20-2009 20:51

The part is laid down, web horizontal to the floor and either a string or I guess a laser could be shot across from one end to the other. Measure the distance the beam is cambered. Once the beam is stood up, the weight of itself may make the camber less, thats why it HAS to be checked in the unloaded position. It can not be correctly checked if its installed. (we've had third party inspectors try that with a cement floor poured onver cmabered beams and they said we never cambered the piece.)

By 803056

Date 05-24-2009 13:08

Never check camber once the beam is received in the field. It may (will) not be the same as it was when it was loaded on the truck for transport.

A while back I heard of a project where the girders were cambered in the wrong direction. The fabricator followed the print, but the print was wrong and no one cought it until the GC questioned why it was taking so much concrete to level the bridge deck.

Best regards - Al