An example of how the plots could help the designer...HarryvL wrote: ↑Thu May 24, 2018 4:55 amWorth seeing how reinforcement ratio translates into required area of bars, but what is immediately clear from the first plot:
FreeCAD: Required Ratio_x top ~ 1.3 * Ratio_x_mid_span
Design: 4 Ø 12 at top vs. 3 Ø 12 at mid span, so indeed 1:1.3
Above the central support, the required reinforcement in x-direction follows from the following plot:
The required area of steel per area of concrete (on x-section x=constant) varies over the height. This is of course not practical and the x-section needs to be divided in zones with a single reinforcement ratio. In some cases it may desirable to apply several layers of steel in such way, but in this practical example of a beam only a single layer is applied. So in this the case of one layer, the average steel area required is:
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As = Rho_av * Height_of_Zone * Width_of_Zone * Material_Factor = 0.5*0.012*200*200*1.15 = 276 mm^2 3 Ø 10 gives 237 mm^2 (insufficient) 3 Ø 12 give 340 mm^2 (sufficient)
Similar considerations can be applied for the other locations and the other reinforcement ratios.
Again, I need to stress here that I am not a qualified concrete structural engineer, so please don't take this as professional advice, but an invitation for a discussion...