When a specimen of {M} 25 concrete is loaded to a stress level of 12.5 {MPa}, a strain of 500 \times 10^{-6} is recorded. If this load is allowed to stand for a long time, the strain increases to 1000 \times 10^{-6} . In accordance with provisions of IS: 456-2000, considering the long-term effects, the effective modulus of elasticity of the concrete (in {MPa} ) is_________

GATE Civil Engineering (CE) 2019 Shift 2 Solved Paper

Question : 37 of 65

Marks: +1, -0

When a specimen of

{M} 25

concrete is loaded to a stress level of

12.5 {MPa}

, a strain of 500

× 10^{-6}

is recorded. If this load is allowed to stand for a long time, the strain increases to 1000

× 10^{-6} .

In accordance with provisions of IS:

456-2000

, considering the long-term effects, the effective modulus of elasticity of the concrete (in

{MPa}

) is_________

Solution:

Short term strain

=500 × 10^{-6}

Long term strain

=1000 × 10^{-6}

So, creep coefficient,

θ=\;{(1000-500) × 10^{-6}}/{500 × 10^{-6}}

θ=1

Long-term effective modulus

=\;{E_{s}}/{1+θ}=\;{5000 √{25}}/{1+1}

=12500 {N} \/ {mm}^{2}=12500 {MPa}

{E}_{α}=\;{\;\text " Stress "\;}/{\;\text " Long term straln "\;}

=\;{12.5}/{1000 × 10^{-6}}=12500 {MPa}

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