Design Considerations
(a) The steel section shall be considered as carrying the entire load, but allowances may be made by assuming the radius of gyration 'r' of the column section about the axis in the plane of its web to be 0.2 (b0 + 100). The radius of gyration about its other axis shall be taken as that of the uncased section.
(b) The axial load within the encased column < 2 × (axial load permitted on uncased section).
(c) An slenderness ratio of uncased section for its full length centre to centre of connection) < 250.
(d) Within computing the allowable axial load on the encased strut, the concrete shall be taken as assisting in carrying the load over its rectangular cross section, any cover in excess of 75 mm from the overall dimensions of the encased steel section to be ignored.
(e) The permutable compressive load P shall be determined as follows:
P = Asc σsc + Ac σc ,
where, Asc , Ac = Cross sectional area of steel and concrete; and
σsc, σc = Permissible stresses in steel and concrete in compression.