According to Indian standard code IS: 1343-1980, permissible unit bearing pressure on concrete after allowing for all losses is limited to: 0.48f_ci (A_br/A_pan) or 0.8 f_ci, f_ci = cube strength of concrete at transfer, A_br= bearing area, A_pan = punching area.

Closely spaced spirals reinforcement increases ultimate load capacity of column due to confinement of concrete in core and spirals are particularly useful in increasing ductility of member and hence are preferred in high earthquake zones.

The compression failure mode develops under concentric loading and this type of failure mode develops under concentric loads and section is considered to have failed when concrete strain ?0 reaches a value of 0.02.

The area of high tensile and un tensioned reinforcement required to mobilize desired flexural strength is computed using force equilibrium at limit state of collapse and force equilibrium rar depends upon pressures exerted in different conditions.

In case of pre tensioned members, computations of transmission length at ends is of practical significance since support positions are influenced by bond and transmission length.

Curved cables are advantageous in reducing effective shear and toger with horizontal compressive prestress, reduce magnitude of principal tension and effect of shear is to induce tensile stresses on diagonal planes and prestressing is beneficial since it reduces magnitude of principal tensile stress in concrete.

For flanged sections, m_ud = 0.08f_ckbd² assuming b = 0.5d and b_w = 0.25b, d³ = ((1200×106)/0.10x35x0.5)), d = 1000mm, b = 500mm, thickness of top flange = h_f = 0.2d = (0.2×10000) = 200mm, thickness of web = b_w = 0.25b = (0.25×500) = 125mm
Assuming neutral axis depth, x_u = hf = 200mm, m_u = 0.87f_pA_p (d-0.42xu), A_p = (m_u/0.87f_p (d-0.42xu)) = (1200×10⁶/0.87×1500(1000-0.42×200)) = 100³mm².

Bennett has proposed design charts with dimensionless parameters expressed in terms of service loads and moments, and section properties and permissible stresses in concrete expressed as a fraction of characteristic strength se charts are useful in dimensioning columns of I section with non uniform prestress and allowing desirable tensile stresses in concrete as in class 3 type members.

force of cable = 200kn, b = 100mm, d = 200mm
Bearing area A_br = (100×100) = 10000mm²,
Actual bearing pressure = (200×10³) / 10000 = 20n/mm².

The load contour method of analysis, detailed by Nawy and generally termed Bresler-Parme counter method is ideally suited for design of biaxially loaded columns and design procedure is outlined following steps: give ultimate moments, determine larger of equivalent required, assumed cross section, verify ultimate load carrying capacity, calculate actual nominal moment capacity, moment value.