Concrete Technology (341-354)

Updated: Apr 30, 2020

341.

1.The condition that Ld < (M/V + L0) need not be checked for negative

reinforcement

2. At least one-third of the total negative reinforcement provided must extend beyond the point of inflection for a distance not less than d, or 12 Φ or

clear span whichever is large


342. In a RCC beam of breadth b and overall depth D exceeding 750 mm, side face

reinforcement required and the allowable area of maximum tension reinforcement shall be respectively 0.1 % and 0.04 bD


343. In limit state design of reinforced concrete, deflection is computed by using

short and long-term values of Young's modulus

344. As per IS:456-1978 the vertical deflection limit for beams may generally be assumed to be satisfied provided that the ratio of span to effective depth of a continuous beam of span up to 10 m is not to be grater than 26

345. Negative moment in reinforced concrete beams at the location of supports is

generally much higher than the positive span moment. This is primarily due to

curvature at the supports being very high

346.









347. In the conventional prestressing, the diagonal tension in concrete Decreases

348. Beam sections of reinforced concrete designed in accordance with ultimate

strength or limit state design approach, as compared to section designed by working stress method for the same conditions of load and span, and the same width, usually have smaller depth and more reinforcement

349. A doubly reinforced beam is considered less economical than a singly reinforced beam because compressive steel is under-stressed

350. The ultimate strength of the steel used for prestressing is nearly 1500 N/mm²

351. Assertion A: In the working stress method, the stress in compression steel is taken as 1.5 x modular ratio x stress in surrounding concrete.

Reason R: The modulus of elasticity of concrete in compression is only two-thirds

of that intension.

352. Assertion A: Losses in prestress of pretensioned beams are more than the

losses in post-tensioned beams.

Reason R: This is partially due to the effect of elastic shortening.



353. Assertion A: The development length for HYSD Fe 415 bars is less than that for

mild steel plain bars.

Reason R:The permissible bond stress for HYSD Fe 415 bars is more than that for

mild steel plain bars

354. Assertion A: Bridges designed for class AA loading should be checked for class-A Loading also.

Reason R: Under certain conditions, heavier stresses may be obtained for class

A loading.



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