162. The minimum cube strength of concrete used for prestressed member, is

A. 50 kg/cm2

B. 150 kg/cm2

C. 250 kg/cm2

D. 350 kg/cm2

163. High strength concrete is used in prestressed member

A. to overcome high bearing stresses developed at the ends

B. to ovecorne bursting stresses at the ends

C. to provide high bond stresses

D. all the above.

164. Pick up the assumption for the design of a prestressed concrete member from the following :

A. A transverse plane section remains a plane after bending

B. During deformation limits, Hook's law is equally applicable to concrete as well as to steel

C. Variation of stress in reinforcement due to changes in external loading is negligible

D. All the above.

165. If the tendon is placed at an eccentricity e below the centroidal axis of the longitudial axis of a rectangular beam (sectional modulus Z and stressed load Pin tendon) the stress at the extreme top edgePZPe

A. is increased by ?e

B. is increased by ?Z

C. is decreased by Pe

D. remains unchanged.

166. In a prestressed beam carrying an external load W with a bent tendon is having angle of inclination 0 and prestressed load P. The net downward load at the centre is

A. W ? 2P cos 0

B.W ? P cos

C. W ? P sin 0

D. W ? 2P sin 0

167. If the loading on a prestressed rectangular beam, is uniformly distributed, the tendon to be provided should be

A. straight below centroidal axis

B. parabolic with convexity downward

C. parabolic with convexity upward

D. straight above centroidal axis

168. If a rectangular prestressed beam of an effective span of 5 meters and carrying a total load 3840 kg/m, is designed by the load balancing method, the central dip of the parabolic tendon should be

A. 5 cm

B. 10 cm

C. 15 cm

D. 20 cm

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