AASHTO LRFD - Deck Design

[RME1]

Hi,

I'm looking at designing the deck slab for a fairly routine, simply supported, multigirder bridge deck.
Being from the UK, I have not used AASHTO before and have a quick question regarding the anaysis.
Ordinarily, I would look at the global effects of differential deflection of the beams imposing a moment into the deck, and then add the local wheel effects of the slab spanning between 2 beams using pucher charts or a plate/shell model.
From looking at aashto, the approach seems to be much simplyfied to either the emperical check or a quick line beam model using a strip analysis.

Am I missing something or is it really that simple?

 

[Qshake]

RME1 -

I have had the pleasure of designing two bridge slabs in the UK and Ireland and will note that yes, our AASHTO is that simple!

Our slab designs (many can be seen from various State DOT websites) are typically controlled by a wheel line load load applied at the appropriate distance from the curb and a unit length investigated. Another controlling load case may be the collision load applied at the top of the safety barrier curb, again acting on the cantilever portion of the deck. Rarely will the slab design be controlled from the interior span between girders. In most cases, the same reinforcing used for the negative moment (cantilever) is also used for the positive moment (girder distance). We do use a lot of precast panel construction and since the panels are standard designs many do not design them but rather select them based on loading and distance between girders to determine the panel thickness. In the case of panel construction only the top mat of steel is required to be deisgned.

I hope this helps. Good luck. You'll find it a lot different in just the terminology! At least I did.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[RME1]

Thanks Qshake,

Precast panels with an in-situ topping have been proposed, so this sounds like a pretty standard case. We have a concrete barrier/parapet/railing on the stringcourse/cantilever/overhang, so I guess this will govern the design.

RME1