Limit deformation:

Starting situation

The spillways are placed inside of flood rooms and drain to the river if the water level of the flood rooms exceeds the level of the spillways. When the river has higher water the situation is reversed and the spillways drain from the river into the flood rooms. So there are two situations to be calculated: Water filled spillway and empty spillway with bouyant forces.

What we did

In a first step we calculated the limit load of the spillway shells based upon the theory of large deflections. The verification was done using a simplified hand calculation. This kind of verification was decided to be acceptable because of the low cycle loading of the spillway. By allowing and considering large deflections and post-buckling behaviour we considerably were able to reduce the wall thickness compared with calculations according to DIN18800, which is the german standard for steel constructions. Additionally and to approve the assumptions of the above simplified verification a fe-calculation was led. The fe-calculation considered the nonlinear material law for stainless steel and the nonlinear geometry for the postbuckling behaviour. The limit load was calculated also verifying the limit plastic strains of the material. It could be shown that the limit load of the spillway is not exceeded with the plate buckling of the shells but with the remarkable higher local buckling of the folded edges.