Modelling manhole in STAAD.Pro

[francis_intano]

Good day!

I'd like to ask whether to model the circular manhole in STAAD.Pro with or without the holes. We do think the walls in between holes would be the most critical area, however actually modelling a circular manhole with circular cutout is tedious work. Putting loads such as hydrostatic and earth pressure is also another hassle. Is it alright to forgo the pipe cutout and assume a circular section for simplicity? Obviously modelling it wit pipe cutout would be better, but I can't get around with putting a linearly increasing pressure.

Thanks for your help!

 

[JoshPlumSE]

Personally, I'd start with simplicity and use a little extra safety.

Also, I'd suggest that you don't really have to model the cutouts as circular If you modeled them as an octagon that's probably good enough. Start with a square equal to the diameter of the hole, then add in triangular plates at the corners.

 

[WARose]

Also, I'd suggest that you don't really have to model the cutouts as circular If you modeled them as an octagon that's probably good enough. Start with a square equal to the diameter of the hole, then add in triangular plates at the corners.

I normally model circular openings as square. The stress concentrations are higher.....but it is faster.

 

[JoelTXCive]

I'm confused. Are you talking about the cast iron cap of a manhole?

Or, the concrete manhole riser and junction box below?

If it is the concrete riser, then there are lots of design resources available online at the American Concrete Pipe Association (

http://www.concrete-pipe.org)

or National Precast Concrete Pipe Association (NPCA)