huangyhg

metric rebar call-outs
what's "12Ø20" mean?
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doesn't look like a standard way of scheduling rebar.
should be, as an example:
12 t20 20 160
which would be 12 x 20mm diameter high yield bars, barmark 20 (then from the bending schedule you can get the shape code and full dimensions) at 160mm spacing
so in summary i don't know what it means
ok, that's a start.
the call-out in particular referred to slab reinforcing. by counting up the dots representing individual rebars, the twelve (12) referred to 12 bars per meter. this was consistent with other similar call-outs on the drawings (these aren't shop drawings). and like those other similar call-outs, the Ø20 i took to mean "diameter - 20" as in 20 mm diameter. the only problem was, my handy reference card from astm doesn't have a 20 mm bar; it has a 19 bar...
sorry i know nothing about these american standards - 19mm bar!! metric sizes are 12, 16, 20, 25, 32, 40mm
well, that's a seriously good answer: in the usa, at least not to my knowledge, we don't have 20 mm rebar. thusly, the bars are 20 mm in diameter. that makes my check of the engineer's work match perfectly. thank you, zambo!
suggest, though, when dealing with metric sizes you need to be careful. for example: in indonesia, the metric sizes are 6, 8, 10, 13, 16, 19, 22, 25, 29, 32, 36, 40, and 50. in india, they are 8, 10, 12, 16, 18, 20, 22, 25, 28, 32, 36, 40 (and there are others - 18 in total i believe). these are actual diameters. in canada, they use bar designations - so a 10m bar is really 11.3 mm in diameter; a 15m bar is 16 mm, a 45m bar is 43.7 mm dia. see link below for canadian bar designation vs diameter.
#12 @ 20 cm o.c.
canada uses nominal bar sizes, where the diameter is slightly different from the designated size, in order to get nicely rounded cross-sectional areas.
10m - 11.3 mm dia - 100 mm^2
15m - 16.0 mm dia - 200 mm^2
20m - 19.5 mm dia - 300 mm^2
etc...
the us metric sizes are also nominal designations, such as #10 which has an actual diameter of 9.5 mm which in turn is a hard (mostly) conversion from the us customery unit size of 0.375 inches. us bar production is still to the old sizes in inches.
presumably some other countries use nominal sizes for similar reasons.

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