[1985 Ed.
!
B 90
[Subsidiary]
CAP. 123] Building (Construction) Regulations
(c) The bar shall extend at least 12 bar diameters beyond the point at which it is no longer required to resist stress.
(d) For the purposes of this paragraph, the length of the bar so determined may have deducted from it a length equivalent to the value of the hook as given in paragraph (5) but no deduction shall then be made for the length of the bar contained in the hook.
(2) (a) The local bond stress calculated from the formula-
Q
160
where-Q
la
is the total shear force across the section;
is the arm of the resistance moment; and
0
is the sum of the perimeters of the bars in the tensile reinforcement,
shall not at any point exceed the permissible local bond stress given in regulation 116.
(b) In members of variable depth the effect of the change in depth shall be taken into account in calculating the bond stress.
(3) Hooks and other anchorages of reinforcement shall be of such form, dimensions and arrangement as will ensure their adequacy without over-stressing the concrete or other anchorage material.
(4) (a) A hook at the end of a mild steel bar shall be of the form indicated in Diagram 4 with an internal radius of the bend not less than 2 times the diameter of the bar, and a length of straight bar beyond the end of the curve of at least 4 times the diameter of the bar, except that where the hook fits over a main reinforcing or other adequate anchor bar, the radius of the bend may be reduced to that of the main reinforcing or anchor bar.
DIAGRAM 4
Standard hook for mild steel bars
radius 2D unless round main bar
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