Civil Engineering - Theory of Structures - Discussion

1. 

If a concrete column 200 x 200 mm in cross-section is reinforced with four steel bars of 1200 mm2 total cross-sectional area. Calculate the safe load for the column if permissible stress in concrete is 5 N/mm2 and Es is 15 Ec

[A]. 264 MN
[B]. 274 MN
[C]. 284 MN
[D]. 294 MN
[E]. None of these.

Answer: Option C

Explanation:

No answer description available for this question.

Nazeer said: (Mar 3, 2016)  
How is it done?

Bapan Halder said: (Jul 25, 2016)  
P = 5 * {(40000 - 1200) + (1200 * 15)}.

Mrinal Kanti Biswas said: (Aug 12, 2016)  
P = 5*(200*200-1200) + (1200*15) = 212000 N

So the answer is E.

Abhishek.Kumar said: (Sep 14, 2016)  
Sir. Plese tell me the correct answer with explanation.

Nishant Jain said: (Oct 15, 2016)  
Ans is C.

Find permissible stress[$] in steel first as:

Permissible stress in steel/permissible stress in concrete = Es/Ec.
Permissible stress in steel = 5 * 15Ec/Ec = 75.

Now solve:
P = 5 * (200 * 200 - 1200) + (1200 * 75) = 284000N = 284.

Shiva said: (Oct 1, 2017)  
Explain this with formula.

Chulbul said: (Jan 31, 2018)  
As the elongations are equal, use the formula.

Strain= stress/Young's modulus.

Maniesh said: (Apr 7, 2018)  
Stress= load/ area,
Stress in steel = load / area of steel and likewise same for concrete,

Es= permissible stress in steel/ strain in steel and likewise same for concrete,
strain in concrete and steel are same = permissible stress in steel/ Es= permissible stress in concrete/ Ec.

Es= 15Ec.
=permissible stress in steel= permissible stress in concrete/ Ec xEs =( 5 /Ec)x 15Ec= 75Mpa for steel.
Load = permissible Stress in steel x area of steel +permissible stress in concrete x area of concrete.
= 75 x 1200+ 5 x (200X200 -1200)= 284kN.

Kisan Prasad Gaire said: (Mar 28, 2019)  
Excellent explanation, Thanks @Maniesh.

Abhishek said: (Apr 10, 2019)  
Thank you for explaining.

Raju said: (Jun 13, 2019)  
Thank you @Maniesh.

Roy said: (Sep 15, 2019)  
So,modular ratio is m=Es/Ec=15.

Stress in steel, t=mc=15*5 = 75mpa.

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