B 74
CAP. 123]
Building (Construction) Regulations
[1985 Ed.
[Subsidiary] Effective length of columns.
Stresses due to wind.
L.N. 294/76.
Longitudinal reinforcement for columns.
L.N. 294/76.
119. For the purpose of regulation 118 the effective length of a column shall be--
(a) in the case of a column specified in Table XXXI, that
specified in column 2 of that Table; and
(b) in the case of a column not so specified, that determined to
the satisfaction of the Building Authority.
TABLE XXXI
Effective column length of reinforced concrete columns
1
Type of column
Properly restrained at both ends in position and
direction
Properly restrained at both ends in position and
at 1 end in direction.
Properly restrained at both ends in position but
not in direction
Properly restrained at 1 end in position and direction and at the other end partially restrained in direction but not in position. Properly restrained at 1 end in position and direction but not restrained at the other end
2
Effective column length (L = length of column between centres of restraining members)
0.7 L
0.85 L
L
1.5 L
2.0 L
120. The stresses in reinforced concrete may exceed the permissible stresses specified in regulations 116, 117 and 118 by not more than 25 per cent.
Provided that-
(a) such excess is solely due to stresses induced by wind
loading; and
(b) except as provided in regulation 158(2) the maximum
stress in reinforcement shall in no case exceed 185 MPa.
121. (1) The aggregate cross-sectional area of the longitudinal reinforcements in a reinforced concrete column shall be not less than 0.8 per cent nor more than 4 per cent of the gross cross-sectional area of that column required to transmit all the load.
(2) Where the longitudinal reinforcement in any column is continuous without laps and where the least lateral dimension of the column is not less than 375 mm, the maximum percentage of the longitudinal reinforcement may be increased to 8 per cent.
(3) A reinforced concrete column having helical reinforcement shall have not less than 6 longitudinal reinforcements placed equidistantly around the inner circumference of, and in contact with, the helical reinforcement.