Live load analysis - culvert design 1

[Nayan67]

Hello everyone,
I am designing a three cell box culvert. I am trying to perform a live load analysis in the culvert to estimate the forces in the slab and wall. I have realized that unlike point loads in bridges, we need to apply the vehicular load as an area load due to live load dispersion over buried structures. So, I am curious whether we need to condcut a moving load analysis for these dispersed loads in the culvert or there is other standard way to handle the live load analysis in culvert. My curiosity stems from the fact that the software I am using to estimate the forces does not have an option of moving load anlaysis for the dispersed load.

Regards,
Nayan

 

[GeorgeTheCivilEngineer]

I used to do this full time early career... the span were quite modest so it didn't really matter because you'd only get full effect of one wheel load. So then just mid-span for bending and support for shear.

If it is three independent spans then that is probably still the case. If it is a continuous three spans then I'd be more inclined to do a more refined analysis.

 

[WesternJeb]

Most states have standardized design tables for box culverts. If you are in the US, look up your state and their standard transportation details.

 

[Nayan67]

George, thank you so much.
WesternJeb, I am not in the US but we follow AASHTO guidelines for the design. If possible, can you please share me the link or standardized design tables for box culverts of any state?

 

[WesternJeb]

This is Kentucky's (see link below). The standardized box culvert designs are around halfway down and based on spans, BSC001-BSC007. Obviously, use these with caution and explore the other standards on the website so you understand what all goes into it. KY Transportation Cabinet also designs to AASHTO standards plus 25% I believe, so the design might seem conservative if you're just running AASHTO numbers.

edit: I encourage you to do the design yourself and use the standard drawings as a check for yourself instead of just trusting it blindly.

https://transportation.ky.gov/Highway-Design/Pages/2020-Standard-Drawings-Bridges.aspx

 

[Nayan67]

WesternJeb,
Thank you for the link. For your information, the culvert I am designing has three spans with the total total width of 14.0 meters. I guess the standard details might not work in my current case. Anyway, the link has many resources and will surely be of help in the future.
Thank you again.

 

[robyengIT]

you can youse (free download)the software "CANDE"

 

[triops1996]

Ultimate answer to your question is yes you have to do a moving load analysis.

You could conservatively assume no dispersion of live load if end result is acceptable (not overly conservative).

Some software may allow you to hard input multiple lane loads which might be able to get the desired effect.