Concrete Excavation
Concrete Excavation
(OP)
Hello again,
I am trying to find areas of maximum internal bending moments in the walls of a concrete structure. The shape of the structure is a rectangular box and is quite massive (about 5m x 7m x 30m). The structure is underground and will experience varying pressures along the side walls. I have modelled this structure using an FEA program but I also want to compare those results with hand calculations. What is the best way to approach this problem?
Thanks
I am trying to find areas of maximum internal bending moments in the walls of a concrete structure. The shape of the structure is a rectangular box and is quite massive (about 5m x 7m x 30m). The structure is underground and will experience varying pressures along the side walls. I have modelled this structure using an FEA program but I also want to compare those results with hand calculations. What is the best way to approach this problem?
Thanks
RE: Concrete Excavation
You can take each face individually, treat it as a flat plate, apply whichever of Roark's formulas seems to fit the best, and check loading in that way. Check it assuming simply supported and with fixed edges, and assume your case is somewhere in between.
You can isolate a section out of the box, treat it as a square frame, and design for bending in that direction.
You can treat the faces as slats running in the short direction, check reinforcing in that direction, then treat as slats crosswise and check reinforcing in that direction.
Roark may even have some equations for a rectangular tank which could be applied.
In any case, you may be able to come up with a satisfactory design by hand, but you could have some pretty wide variations between the design and FEA model.
This kind of problem is vastly simplified in many cases when the reinforcement required by loading falls below the required minimum areas- then you can make some pretty appoximate, but conservative assumptions, and still have a reasonable design.
RE: Concrete Excavation
The Reinforced Concrete Designers Manual has worked examples for this type of design. (UK publication).
RE: Concrete Excavation
I did look at the Reinforced Concrete Designers Manual (not sure what publication) but I was unsure whether or not I could consider this a straightforward rectangular culvert due the massive size of the structure. Though sectioning the model into 1m length box culverts may be a fair approximation. I'll try that out.
RE: Concrete Excavation
http://
It's set up for liquid retaining tanks, and I think your worst case will be when the tank is empty. So in that case your moments will be opposite of the table moments. I will have to look if the aspect ratio goes as high as the tank you have.