As we know , RSA d sections efines columns with their sections and parameters E & stiffness & inertia . So, column is an area under slabs (sla supports on ares section of column) . am i true ?
why is there a reducton of moment over supports ?
Please i want to understant this topic 🙂
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Solved by Artur.Kosakowski. Go to Solution.
Im not sure for this one, but perhaps Robot is taking in account that in reality there will be no pointy, very high, forces on that place. When you support your slab with a column, on the point of support you get very high moment, which are not likely to happen in reality (some cracking in the upper zone will always occur, therefore the moment in that section will be smaller than it was calculated in model).
For FEM the results of bending over point support are higher than the real ones (they increase the smaller size of mesh elements you generate) which is the effect you want to avoid for reinforcement calculations.
See also: http://forums.autodesk.com/t5/Robot-Structural-Analysis/reduction-of-value-near-supporte/m-p/4699379
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I already define supports as columns , but when i check the reduction button , the moment value and shape change .
I follow posts which are posted here in the forum and accidentaly know the concept of reduction in RSA .
The value of moment decreases into the half of its unreduced value.
The real size of the support (e.g. a column) is disregarded for the classic FEM solution (bars elements and shells) as it is only the attribute of either a node or a bar element (being a dimensionless line). Only when you mark the reduction check box these results are averaged with values from the neighborhood according to the method described in Help. The effect of a real cross section of a column (without the reduction option being used) would be visible when you model it as a volumetric (solid) element instead.
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it would be better if this is merged in the basic inner calculation in RSA .
I can understand your point of view however I personally prefer to understand a how a given option works and then have full control on its application meaning that I can use it or not depending if I think it makes sense in a given situation