With the exception of where bars are spliced ~
BEAMS
The distance between any two parallel bars in the horizontal
should be not less than the greater of:
25 mm
the bar diameter where they are equal
the diameter of the larger bar if they are unequal
6 mm greater than the largest size of aggregate in the concrete
The distance between successive layers of bars should be not less
than the greater of:
15 mm (25 mm if bars > 25 mm dia.)
the maximum aggregate size
An exception is where the bars transverse each other, e.g. mesh
reinforcement.
COLUMNS
Established design guides allow for reinforcement of between 0„8%
and 8% of column gross cross sectional area. A lesser figure of
0„6% may be acceptable. A relatively high percentage of steel may
save on concrete volume, but consideration must be given to the
practicalities of placing and compacting wet concrete. If the design
justifies a large proportion of steel, it may be preferable to
consider using a concrete clad rolled steel I section.
Transverse reinforcement ~ otherwise known as binders or links.
These have the purpose of retaining the main longitudinal
reinforcement during construction and restraining each reinforcing
bar against buckling. Diameter, take the greater of:
6mm
0„25¾main longitudinal reinforcement
Spacing or pitch, not more than the lesser of:
least lateral column dimension
*^12 ¾diameter of smallest longitudinal reinforcement
300 mm
Helical binding ~ normally, spacing or pitch as above, unless the
binding has the additional function of restraining the concrete core
from lateral expansion, thereby increasing its load carrying
potential. This increased load must be allowed for with a pitch:
not greater than 75 mm
not greater than 0.166¾core diameter of the column
not less than 25 mm
not less than 3¾diameter of the binding steel
Note: Core diameter is measured across the area of concrete
enclosed within the centre line of the binding.
Spacing of Reinforcement Bars