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GATE CE 2022: RCC & Prestressed Concrete Quiz#8

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Question 1

A simply supported rectangular concrete beam of span 8m has to be prestressed with a force of 16001(N. The tendon is of parabolic profile having zero eccentricity at the supports. The beam has to carry an external uniformly distributed load of intensity 30 l(N/m. Neglecting the self-weight of the beam, the maximum dip (in meters, up to two decimal places) of the tendon at the mid-span to balance the external load should be

Question 2

A pre-stressed concrete beam of cross-sectional area A, Moment of inertia I, distance of NA from extreme top fibre is yt and from bottom axis is yb is subjected to a pre-stressing force such that the stress at top fibre is zero. What is the value of eccentricity? (radius of gyration r)

Question 3

Statement (I): Loss due to prestress in a pretensioned beam is generally more than that in a post tensioned beam.

Statement (II): Loss due to elastic shortening does not take place in post tensioned beams

Question 4

The ratio of frictional loss due to curvature effect to that of wobble effect if jacking is done from both ends will be _____ (Take μ = 0.3, k = 0.003/m).

Question 5

A rectangular presressed concrete beam of span 15 m and width 500 mm is loaded with a live load of 30 kN/m. The prestressing force is ______ kN.
[Take permissible stresses in concrete and steel as 15 MPa and 1200 MPa respectively]

Question 6

A concrete beam prestressed with a parabolic tendon is shown in the sketch. The eccentricity of the tendon is measured from the centroid of the cross–section. The applied prestressing force at service is 1620 kN. The uniformly distributed load of 45 kN/m includes the self–weight.

The stress (in N/mm2) in the bottom fibre at mid–span is
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