Subsequent are the permissible stresses:
(a) Permissible stress in direct tension (σat) in MPa, on the net effective area of the section is
σat = 0.6 fy
where fy = Minimum yield strength in MPa.
(b) Permissible stress in direct compression (σac) should not exceed 0.6 fy (which is the case of non-slender axially loaded compression members; the gross sectional area of the member is to be taken)
σac ≤ 0.6 fy
In case of slender elements (slenderness ratio λ= l/ r exceeding 10), σac should be calculated by the following formulae
σ ac ≤ 0.6 f cc ⋅ f y/[fcc n + fy n ]1/n
where fcc = Elastic critical stress in compression = π 2 E/λ2
where E = Modulus of elasticity of steel = 2 × 106 MPa
λ = Slenderness ratio = l /r = Effective length/Minimum radius of gyration
n = A factor assumed as 1.4.
(c) Permissible compressive stress due to bending (σbc) is given by
σbc ≤ 0.66 fy
For beams and the plate girders bent about axis of maximum strength (x-x axis)
σbc ≤0.66 fcb ⋅ f y/[fncb +fny]1/n
where fcb is the elastic critical stress in bending and depends upon T/t and d/ l.
(d) Permissible tensile stress because of bending (σbt) is given by
σbt ≤ 0.66 fy
(e) Bearing stress (σp) computed on net area of contact is given by
σp ≤ 0.75 fy
(f) Permissible shear stress (τva) within a flexural member having regard to the distribution of stresses in conformity with the elastic behaviour of the member is given by
τva ≤ 0.45 fy