Concrete Technology (261-280)

Updated: Apr 30, 2020

261. For Courbon's reaction coefficient to be valid there should be at least five transverse beams


262.For an over-reinforced (singly reinforced) rectangular RC section

1. the lever arm will be less than that for a balanced section

2. the maximum stress developed by concrete would equal allowable stress

in concrete


263.The effective depth of a singly reinforced rectangular beam is 30 cm. The section is over reinforced and the neutral axis is 12 cm below the top. If the maximum stress attained by concrete is 50 kg/cm² and the modular ratio is 18, then the stress developed in steel would be 1350 kg/cm²


264.For plain concrete used in underground works of moderate exposure condition, the minimum cement content (in kg/m³) of the concrete mix would be

250

265. Which one of the following statements about the percentage of tensile steel

required to produce a balanced reinforced concrete section is correct ?

reduces as the yield strength of steel increases.

266. Which of the following are not dependent on the applied load?

1.Drying shrinkage strain

2. Carbonation shrinkage

267. Marcus correction is introduced as simple correction to

moments obtained by Rankine Grashoff method to allow for corner

268. The radial moment at the boundary of a simply supported circular slab of radius R, subjected to a uniformly distributed load of w will be zero

269. The hoop stress in a dome subjected to uniformly distributed load is tensile at sections whose radius

vectors are at angles greater than

5151' with the vertical

270. For the normally used values of material properties and curing conditions, the maximum percentage of loss of prestress in post-tensioned concrete occurs due to creep and shrinkage of concrete

271. Concordant profile represents, for a certain set of external loads to some scale,

the bending moment diagram

272. The loss of prestress due to shrinkage of concrete is the product of modulus of elasticity of steel and shrinkage of concrete


273. For a given grade of steel, the limiting reinforcement index for a singly

reinforced beam is proportional to fck

274. While applying the Winter and Pei's method of analysis to folded plates

displacement of the junction of hipped plate can be ignored if the

span/depth ratio is less than 4

275. Minimum clear cover (in mm) to the main steel bars in slab, beam, column and footing respectively are 15, 25, 40, 75

276. The main reinforcement of a RC slab consists of 10 mm bars at 10 cm spacing.

If it is desired to replace 10 mm bars by 12 mm bars, then the spacing of 12 mm

bars should be 14.40 cm

277.

Maximum longitudinal reinforcement in an axially loaded short column is 6 % of gross sectional area


278. Torsion resisting capacity of a given RC section increases with the increase in stirrup and longitudinal steels.

279. If a simply supported concrete beam, prestressed with a force of 2500 kN, is

designed by load balancing concept for an effective span of 10 m and to carry a total load of 40 kN/m, the central dip of the cable profile should be 200 mm

280. In case of pre-tensioned RC beams

shrinkage of concrete is of the order of 3x 10⁻⁴

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