Box culvert

[maneesha0702]

I am checking a boxculvert. It is a twin cell with 27" sidewalls and 18" midwall. The ht is 15' and span is 20' for each cell.The boxculvert supports 19.5 ft soil on top. The top slab is 42" and has #11@6" for _ve reinforcement and #9@6" for +ve reinforcement. The bottom slab is only 33" thick with #6@6"-ve and #9@6" . I tried to model in RISA 2D. I can not qualify even when using springs as support(250k/in). So top load is 3.2k/ft. Bottom is 4.4k/ft. What am I missing?

 

[JoshPlumSE]

I'm not sure your post is all that clear. I understand what your structure and reinforcement is. But, I don't know what you mean when you say "I cannot qualify even when using springs as support".

My assumption is that you are modeling these as concrete members with the reinforcement described. If so, what is the assumed width of the members.

RISA is going to want to call treat these members as beams or columns, not slabs or walls. Therefore, the reinforcement checks that RISA does on them may not be entirely appropriate. If the walls are referred to as columns, then RISA's going to try to put in 1% of the gross cross section based on minimum reinforcement requirements for columns. But, this wouldn't normally apply to walls.