Encased duct

[Engineermama13]

Need help analyzing strength of encased duct. It is not going to have traffic over it just support it’s own weight. Line is sitting on piles and pile caps. Cross sections images in attachment. Spacing between piles max of 16 ft. Tips on how to analyze?

 

[WARose]

Since I assume the "duct" is not adding anything to the member in terms of strength.....you'd just figure the section properties like there is a hole there. (I.e. it would wind up being like any other transformed area problem.)

 

[KootK]

Capacity's easy:

1) Calc flexure ignoring the hole. Verify that hole doesn't encroach on compression block.

2) Calc shear assuming you've only got the two full height legs of concrete either side of the duct to work with.

Usually it's demand that annoyingly hard to sort out on these things.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Ingenuity]

It is not going to have traffic over it just support it’s own weight.

With a DEMAND of only its self weight, and a max span L of 16', with a depth of D > 3', your L/D < 5. It is not going to take a whole lot of analysis to make this work.