TGPSC HMWSSB Manager 2015 Paper 2 · Question 149

Question 149 of the TSPSC Manager (Engineering), HMWSSB, 2015: Paper 2 (Civil Engineering) (1 November 2015). Try it first, then open the answer and explanation.

1. Manager 2015 Paper 2 (Civil) · Q149 · RCC, Steel & Prestressed Design · Prestressed Concrete

   The loss stress due to creep in steel in a pre-stress problem is given by the formula ______, where α = creep coefficient, f_c = stress in concrete, E_c = modulus of elasticity of concrete and E_s = modulus of elasticity of steel.

   1. α(f_c/E_c) E_s
   2. α(f_c/2E_c) E_s
   3. α(f_c/E_s) E_c
   4. 2α(f_c/E_c) E_s
   Show answer

   Answer: (1) α(f_c/E_c) E_s

   The elastic strain of concrete at the steel level is f_c/E_c and creep adds α times this strain; the steel shortens by the same amount. So the loss of prestress = α(f_c/E_c)E_s, i.e. α·m·f_c with modular ratio m = E_s/E_c.

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