Wrong. Yet right.
Yesterday I read How to determine the weight of a reinforced concrete column on Civil Engineering Discoveries page1
They propose this info-graphic
The calculation is wrong, because when they add the weight of steel they are counting twice that volume.
The actual “correct” value is:
0.3m×0,3m×3.1m×(2400kg/m³ + 1% × (7850-2400kg/m³)) = 684kg
Yet from an engineering point of view 691.5kg is a “right” value, or better, a “proper” value to use in design because the error is on the “safe side“, as it will increase the design load on the underlying structures, inducing to use slightly stronger foundations and slightly bigger underlying columns.
So at the end of the day it is usually better to count the steel volume twice, using 691 as design weight.
- on a “notorious” proprietary social network ↩︎
