Haunch Thickness Calculations

[bridgeengineer2007]

I am designing a prestressed concrete bridge, and have a question regarding the haunch thickness. The haunch should account for cross slope and vertical curve camber, but what Dead Load Deflection should be used?

It seems that non-composite and composite deflections should be accounted for to achieve the proper deck elevations when all is said and done, however I have been reading that only non-composite deflections are considered. Why is this?

Thanks!

 

[bridgebuster]

The dead load would be your slab; the self-weight of the member is taken up by the camber. Where did you read about omitting the composite deflection?

If you're in the US, check your state DOT standards as to how they calculate the haunch height. There's aslo an AASHTO/NSBA publication on the subject (personallly, I think it's too cumbersome).

 

[bridgeengineer2007]

Thanks for your reply. Do you have the AASHTO/NSBA publication reference by any chance?

I've seen several DOT's examples of haunch calculations that are considering slab deflections only, and not superimposed dead loads once the deck is poured. It seems that these composite load deflections should also be accounted for in the haunch in order to set the deck higher than the actual deck elevations.

 

[bridgebuster]

Here's a link to the NSBA publications. The one you're looking for is G13.1, which actually deals with girder analysis under various scenarios. However, camber is based on deflection.

In NY we include the SDL.

http://www.aisc.org/contentNSBA.aspx?id=20130