1964_BUILDING_(CONSTRUCTION)_REGULATIONS — Page 91

1985 Ed.]

Building (Construction) Regulations

[CAP. 123

B 91

[Subsidiary]

(b) Where hooks are formed in high-yield bars—

(i) the internal radius of the bend shall be at least 3 times the diameter of the bar; and

(ii) the length of straight bar beyond the end of the curve shall be at least 4 times the diameter of the bar.

(5) A bend in a reinforcement bar shall be assumed to have an anchorage value equivalent to a length of bar equal to 4 times the diameter of the bar for each 45 degrees through which the bar is bent:

Provided that—

(a) the radius of the bend shall be not less than 2 times the diameter of mild steel bars, or 3 times the diameter of high-yield bars;

(b) the length of the straight part of the bar beyond the end of the curve shall be at least 4 times the diameter of the bar; and

(c) whatever be the angle through which the bar is bent, the assumed anchorage value shall not be taken as more than equivalent to a length of bar equal to 16 times the diameter of the bar.

(6) In bends in reinforcing bars, the local stress on the concrete shall not exceed 3 times the value permitted in regulation 116 for the concrete in direct compression.

(7) Notwithstanding any of the provisions of paragraphs (1) to (6), in the case of stirrups and transverse ties, complete bond length and anchorage shall be deemed to have been provided when the bar is—

(a) (b)

(i) bent through an angle of at least 90 degrees round a bar of at least its own diameter; and

(ii) the stirrup or tie is continued beyond the end of the curve for a length of at least 8 bar diameters; or

(i) bent through an angle of 180 degrees; and

(ii) the stirrup or tie is continued beyond the end of the curve for a length of at least 4 bar diameters.

(8) (a) A bar in compression shall extend from any section for a distance such that the average bond stress does not exceed the permissible average bond stress given in regulation 116 by more than 25 per cent.

(b) The length measured from such section shall be not less than—

Add – M

the bar diameter × the compressive stress in the bar

5 times the permissible average bond stress.