B 64
[Subsidiary]
CAP. 123]
Building (Construction) Regulations
[1985 Ed.
F
For
does not exceed unity at any point,
where ft = the calculated axial tensile stress:
Ft = total permissible axial stress in tension;
fot = the maximum resultant tensile stress due to bending about both principal axes; and
Grillage beams.
L.N. 294/76.
Effective length of columns and struts.
Fb = total permissible tensile flexural stress in extreme fibres of beams and girders.
(3) In paragraphs (1) and (2) "total permissible" means, in relation to any stress, the maximum permissible stress specified in regulation 97 or 98 (as the case may be) plus, where applicable, the increase on the maximum permissible stress permitted in respect of wind load under regulation 99.
101. The maximum permissible stresses in grillage beams (other than hollow compound girders) may exceed the stresses specified in Table XX by 33⅓ per cent where-
(a) the beams are entirely embedded in concrete not inferior to that designated Grade IIIA in regulation 19; and
(b) the beams are spaced apart so that the distance between the edges of adjacent flanges is not less than 75 mm; and
(c) the thickness of the concrete cover on the top of the upper flanges and at the outer edges of the sides of the outermost beams and at the ends is not less than 100 mm; and
(d) the concrete is properly compacted solid around all beams.
102. For the purpose of regulation 98, the effective length of a column or strut shall be that specified in Table XXV for the type of column or strut specified in that Table.
TABLE XXV
Effective length of columns and struts
Type of column or strut Effective length (L = length of column or strut between centres of restraining members) Properly restrained at both ends in position and direction 0.7 L Properly restrained at both ends in position and at 1 end in direction 0.85 L Properly restrained at both ends in position but not in direction L Properly restrained at 1 end in position and direction and at the other end partially restrained in direction but not in position 1.5 L Properly restrained at 1 end in position and direction but not restrained at the other end 2.0 LNote: The effective length of a column or strut of a type not specified in this Table shall be determined to the satisfaction of the Building Authority.