Concrete Technology (281-300)

281. For prestressed structural elements, high strength concrete is used primarily

because of high modulus of elasticity and low creep.

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282. Prestressed concrete is more desirable in case of cylindrical pipe subjected to internal fluid pressure

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283. Yield line theory results in upper bound solution

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284. If the nominal shear stress (𝜏v) at a section does not exceed the permissible shear stress (𝜏c)

minimum shear reinforcement is still provided

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285. Consider the following statements concerning both the working stress design and ultimate strength design of reinforced concrete.

1. Plane section before bending remains plane after bending

2. The tensile strength of concrete is ignored

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286. In limit state design, permissible bond stress in the case of deformed bars is more than that in plain bars by 60%

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287. If fcu and fy are cube compressive strength of concrete and yield stress of_ steel respectively and Es is the modulus of elasticity of steel, for all grades of

concrete, the ultimate flexural strain in concrete can be taken as 0.0035

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288. Limit state of serviceability for deflection including the effects due to creep,

shrinkage and temperature occurring after erection of partitions and application of finishes as applicable to floors and roofs is restricted to Span/350

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289. Shrinkage deflections in case of rectangular beams and slabs can be

eliminated by putting compression steel equal to tensile steel

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290. In case of 2-way slab, the limiting deflection of the slab is primarily a function of the short span

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291. From limiting deflection point of view, use of high strength steel in RC beam

results in increase in depth

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292. For maximum sagging bending moment at support in a continuous RC beam, live load should be placed on spans next to the adjacent spans of the

support plus alternate spans

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293. Design of one-way RC slabs for concentrated load is done by taking slab strip of width effective in resisting the load

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294. In Pigeaud's coefficient method for the analysis of an interior panel of a T-beam bridge the applicability is restricted, to the case when the wheel load is centrally placed

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295. A T-beam roof section has the following particulars 1500 mm

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296

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297.Minimum percentage area of HYSD reinforcement in a 150 mm thick water tank wall is 0.23

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298. In a load balanced prestressed concrete beam under self load the cross-section is subjected to axial and shear stress

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299. A prestressed concrete beam 150 mm x 300 mm supports a live load of 5 kN/m over a simple span of 8 m. It has a parabolic cable having an eccentricity of

75 mm at mid span and zero at the ends. The prestressing force required to

maintain the net resultant stress at the bottom fibre at mid span as zero under the action of D.L. + L.L. + prestress is 392 kN

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300. A partially prestressed member is one in which tensile stresses and cracking are permitted under service loads.