Exams › GATE › Technical
A post-tensioned concrete member of span 15 m and cross-section of 450 mm × 450 mm is prestressed with three steel tendons, each of cross-sectional area 200 mm². The tendons are tensioned one after another to a stress of 1500 MPa. All the tendons are straight and located at 125 mm from the bottom of the member. Assume the prestress to be the same in all tendons and the modular ratio to be 6. The average loss of prestress, due to elastic deformation of concrete, considering all three tendons is
- 14.16 MPa
- 7.08 MPa
- 28.32 MPa
- 42.48 MPa
Correct answer: 14.16 MPa
Solution
Concrete stress at tendon level from all three tendons is fc = P/A + P*e^2/I = 7.08 MPa (P=900 kN, e=100 mm, A=202500 mm^2, I=3.42e9 mm^4). For sequential post-tensioning the average elastic loss = m*fc*(n-1)/(2n) = 6*7.08*(2/6) = 14.16 MPa.
Related GATE Technical questions
- Read the following statements:
(P) While designing a shallow footing in sandy soil, monsoon season is considered for critical design in terms of bearing capacity.
(Q) For slope stability of an earthen dam, sudden drawdown is never a critical condition.
(R) In a sandy sea beach, quicksand condition can arise only if the critical hydraulic gradient exceeds the existing hydraulic gradient.
(S) The active earth thrust on a rigid retaining wall supporting homogeneous cohesionless backfill will reduce with the lowering of water table in the backfill.
Which one of the following combinations is correct?
- For a traffic stream, v is the space mean speed, k is the density, q is the flow, v_f is the free flow speed, and k_j is the jam density. Assume that the speed decreases linearly with density.
Which of the following relation(s) is/are correct?
- Match the following in Column X with Column Y:
Column X
(P) In a triaxial compression test, with increase of axial strain in loose sand under drained shear condition, the volumetric strain
(Q) In a triaxial compression test, with increase of axial strain in loose sand under undrained shear condition, the excess pore water pressure
(R) In a triaxial compression test, the pore pressure parameter “B” for a saturated soil
(S) For shallow strip footing in pure saturated clay, Terzaghi’s bearing capacity factor (Nq) due to surcharge
Column Y
(I) decreases.
(II) increases.
(III) remains same.
(IV) is always 0.0.
(V) is always 1.0.
(VI) is always 0.5.
Which one of the following combinations is correct?
- The three-dimensional state of stress at a point is given by σ = [[10, 0, 0],[0, 40, 0],[0, 0, 0]] MPa. The maximum shear stress at the point is
- A 2 m wide strip footing is founded at a depth of 1.5 m below the ground level in a homogeneous pure clay bed. The clay bed has unit cohesion of 40 kPa. Due to seasonal fluctuations of water table from peak summer to peak monsoon period, the net ultimate bearing capacity of the footing, as per Terzaghi’s theory, will
- Consider the statements P and Q.
P: Soil particles formed by mechanical weathering, and close to their origin are generally subrounded.
Q: A activity of the clay physically signifies its swell potential.
Which one of the following options is CORRECT?
⚔️ Practice GATE Technical free + battle 1v1 →