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Beam and Slab Bridge Design

Beam and Slab Bridge Design

Beam and Slab Bridge Design

(OP)
When I learnt prestressed beam design at college, the section properties (e.g. I value) of the girder don’t change with time or construction stage on which equations or inequalities for the estimations of prestress force and I value are formed.

However, the current problem is a beam and slab that concrete is poured on the top of the prestressed beams to form a “slab”. Thus, the section properties of the structure at “transfer” and “service” are different.

Could any bridge man tell me how I can estimate the required prestress force (and min Z values)????

RE: Beam and Slab Bridge Design

You need to treat all facets of the bridge as a single design problem that you're more likely to see in college.  

In college the problems are broken into little pieces for simplicity.  Now you need to pull them altogether.

If you haven't thrown out your books refer to them for your work.  Otherwise invest in a design aid from the post-tension institute or similar organization.

Regards,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

RE: Beam and Slab Bridge Design

This question is related to what you learned in your sophmore level solid mechanics class.  If you don't recall how, talk to your supersivor.  Questions of this sort should not be handled here.  Good Luck.

RE: Beam and Slab Bridge Design

Your local prestress supllier usually has design aids for this sort of question. This is basically an estimate that you can go further into design with.

As with going through the design process, think of the problem from the beam side.
i.e. @ transfer, just the beam
@ deck pour, beam supports beam and deck
@ final, composite section carries live load
etc....

Good luck

RE: Beam and Slab Bridge Design

Check out this web page from PCI.  http://pci.org/publications/bridge/index.cfm

You will find design examples that explain how the superimposed slab interacts with the prestressed beam and how stresses are to be calculated for the intial and final conditions.

RE: Beam and Slab Bridge Design

parapetguy,

Nice link

VOD

RE: Beam and Slab Bridge Design

Prestressed Concrete Analysis and Design by Naaman covers the derivations of Zmin and eccentricity inequality equations for composite beams.

 

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