Bridge Design 1

[pudmud]

I am new to bridge design and am designing a cantilevered retaining wall abutment (with a single row of piles under toe directly below bearing centreline)and have two queries:

1) I am used to working stress design for footings and foundations and am confused with the limit state check for sliding overturning and bearing. The relevant codes AS5100, AS4678 and AS1170.1 all seem to contradict each other. Is the criteria simply Ult. Overturning Moment < Ult. Restoring Moment and when are the uncertainty factors applied?

2) In relation to designing reinforcement for the RC abutment wall, is it a correct assumption to treat the wall as a two way slab for bending and as a column for axial loading?

Any help would be greatly appriciated.

 

[Qshake]

First, I'm surprised that you can get a cantilevered wall abutment to work with just a single row of pile.

That said,

1. You must be into LRFD for the foundation checks and so generally speaking you're going to find the equations of the factored load being less than or equal to the factored resistance. The uncertainty is implicit within the load factors and resistance factors that you need to use.

2. In most cases I've seen and done the wall is not treated as a twoway slab but a beam. Yes, the wall can be treated as a beam column, i.e., with bending and axial loads.

Regards,
Qshake

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

 

[Dinosaur]

You need to talk to your supervisor about this. You should learn from him before going here for basic questions. Good Luck.

 

[VoyageofDiscovery]

Hi pudmud,

From what I can gather, the bridge system you are faced with here is an integral type.

Overturning does not apply, and a different analysis is required replicating the entire system.

I second dinosaur's suggestion to have someone experienced with this type of bridge design first. Specifics can be answered after you become a little more familiar with the type of analysis.

HTH

VOD

 

[Qshake]

Well, if it is integral construction and noting the piles bearing immediately under the centerline bearing it could very well be, but if so, then it is erroneously characterized as a cantilever abutment...agree Dinosaur/VOD?

Regards,
Qshake

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

 

[VoyageofDiscovery]

I agree.

VOD

 

[broekie]

I agree as well. Sounds like an integral abutment to me.

 

[Dinosaur]

Yes, a single row under the bearings made integral with the superstructure is no cantilever wall. And this is why I recommend speaking with the supervisor. It is easy to ask the wrong question when all you can do is type a message. Good Luck