Truss Bridge Modeling

[apsmith81]

I’m having a hard time trying to determine if the open area between truss members should be considered flowable area or if it should be modeled as completely blocked. Any help would be appreciated.
Adam

[Chris G.]

Adam-

Traditional convention is to assume that if water gets that high, there will be sufficient debris to effectively block the open area through the truss. Also, making that assumption provides a conservative result. Therefore many modelers go ahead an consider it blocked. However, you could certainly make the case that if you don’t expect a lot of debris, it will remain open. In which case you’d ignore the truss work in your station elevation points and maybe decrease your weir coefficient slightly to account for the energy loss of the truss sections. Wither way, pretty subjective. I’d suggest running both, and try a range of weir coefficients and see how it affects your results. The objectives of the study, and how much risk the client is willing to take usually will dictate which way you model this.

Why can’t all bridges be single span slabs?!?!

Good luck!
Chris
@RASModel

[apsmith81]

Chris,
Thanks for the advice; I’ll model the open truss area as completely blocked in the first model and see how it reacts.
Adam

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