Fully prestressed members are prone to excessive upward deflections especially in bridge structures where dead loads form a major portion of total service loads and se deflections may increase with time due to effect of creep.

A_ps = (38.5xy) = 154mm², f_pu = 1600n/mm², b = 160mm, f_cu 50n/mm², d = 265mm
(A_psf_pu/bdf_cu) = (154×1600/160x265x50) = 0.116.

The ultimate load includes self weight enhanced by partial factor of safety
?_f1q+?_f2w_min, W_ud = ?_f1q/1-?_f2(W_min/W_ud).

In case of unsymmetrical I girders range of values of h_t/d and b_w/b for economical designs is generally 0.15 to 0.25 and 0.2 to 0.3 respectively, however thickness of web, b_w is designed based on dual criteria shear and housing cables with adequate cover.

E_ce = (E_c/1+?) = (E_c/2.6), ? = 2.6, ?_y = 38.5mm, ?_g = 46mm, ?_p = 74.7mm, resultant maximum long term deflection = (2.6×46)+38.5-(0.85×74.7) = 95mm which is less than code limit (span/250) = 120mm, ? = 0.85.

h_f/d =0.23 and b_w/b = 0.25 and b = 0.5d,
M_u = 0.10f_cubd² d = (3400×10⁶/0.10x50x0.5)^1/3 = 1130mm, h = (1130/0.85) = 1300, b = 600mm, h_f = (0.2×1130) = 250mm, adopt an effective depth, d = 1150mm, thickness of web, b_w = (0.6vu/fth) = (0.6x450x10³/1.7×1300) = 120mm.

W_min/W_ud = KD_cg?(L/h)L/f_cu(d/h)² = 7.5×2400 x 9.81 x 0.125×25 x 6/50x 10⁶x(0.85)² = 0.094
F_cu, concrete cube strength = 50n/mm², effective span = 6m, applied load = 5kn/m, dead load = 1.4, live load = 1.6, ? = 0.125, k = 7.5, D_c = 2400, f_cu = 50n/mm², w_min = (0.094)(9.25) = 0.86kn/m, m_u = (0.125×9.25×6²) = 42knm, v_u = (0.5×9.25×6) = 27.75kn.

High tensile steel and mild steel have been used as un tensioned reinforcement and present practice is to use high yield strength deformed bars which are considerably cheaper than prestressing steel and at same time have higher yield strength and better crack control characteristics by virtue of ir surface configuration as compared to mild steel bars with plain surface.

F_cp = 23.4n/mm², zb is 99×10⁶, stress is 1000
m₀ = (0.8f_cpZ_b) = (0.8 x 23.4 x (99×10⁶/1000)) = 1850knm.

m_g = 3.86×10⁶, m_q = 22.50×10⁶, f_br = 12, loss ratio = 0.8
Z_b > or equal (m_q+(1-?)m_g/f_br) > or equal ((22.50×10⁶)+(1-0.8)3.86×10⁶)/12)
Greater than equal to 182x104mm³.