Correct Answer - Option 2 : 13 MPa

__Concept:__

The loss of stress due to creep in concrete is given as

F_{c} = θmf_{cs}

Where,

θ is the ultimate creep coefficient

m is the modular ratio and it is given as

\({\rm{m}} = \frac{{{\rm{Modulus\;of\;Elasticity\;of\;steel}}}}{{{\rm{Modulus\;of\;Elasticity\;of\;Concrete\;}}}}\)

f_{cs} is the stress in concrete at the level of steel.

The loss of stress due to shrinkage in concrete is given as

F_{s} = E_{s} × ϵ

Where,

E_{s} is the Modulus of elasticity of steel

ϵ is the shrinkage strain in concrete

__Calculation:__

Given,

θ = 1.6, ϵ = 200 × 10^{-6} ; f_{1} = 3f_{2}; E_{s} = 200 GPa and E_{c} = 35.35 GPa

m = 200/35.35 = 5.66

f_{1} = 1.6 × 5.66 × f_{cs} = 9.05f_{cs} N/mm^{2}

f_{2} = 200 × 1000 × 200 × 10^{-6} = 40 N/mm^{2}

It is given that

f_{1} = 3f_{2}

9.05f_{cs} = 3 × 40

**⇒**** f**_{cs} = 13.26 ≈ 13 N/mm^{2}