Concrete Technology (301-320)

Updated: Apr 30, 2020

301. The load carrying capacity of a column designed by working stress method is 500 kN. The collapse load of the column is 750.0 kN


302. Shear span is defined as the zone where shear force is constant


303. Shear cracks start due to high diagonal tension in case of beams with their webs and high prestressing force


304. For ultimate load design of prestressed concrete girders used for bridges,

combination of load factors used is (here DL and LL are dead and live loads

respectively)1.5 D.L.+ 2.5 L.L

305. For a pretensioned rectangular plank the uplift at centre on release of wires from anchors due to pretensioning only (force P, eccentricity e) will be

PeL²/8EI

306.Deflection can be controlled by appropriate

span/depth ratio

307.In limit state approach, spacing of main reinforcement controls primarily

cracking

308. For the section of the beam shown in Fig. 14.2, span of the beam = 6.0 m,

concrete = M20, steel = Fe415.



If the section is checked for serviceability limit state of deflection, then it will be

found that the section is safe

309. Unequal top and bottom reinforcement in a reinforced concrete section leads to shrinkage deflection

310. A pretensioned plank (depth D) is placed over simple supports and additional in situ concrete (depth D) is laid on top. What is the probable shape of stress block on hardening of in situ concrete?







311.Design of foundation for a large generator is guided primarily, by frequency

312




A concrete pedestal made of M20 mix is shown in Fig. The tan a value in this

case will be grater than or equal to 3.6


313. The reduction coefficient of a reinforced concrete column with an effective length of 4.8 m and size 250 x 300 mm is 0.85

314.Given that

d = effective depth

b = width and

D = overall depth

the maximum area of compression

reinforcement in a beam is 0.04 bD

315.The final deflection due to all loads including the effects of temperature, creep

and shrinkage and measured from as-cast level of supports of floors, roofs and all

other horizontal members should not exceed span/250

316



Figure 14.5 shows the position of concentrated wheel loads on a bridge

deck. For determining the bending moments in the girders by Courbon's

theory, the reaction factors are respectively

1.80 W, 1.33 Wand 0.87 W

317. A reinforced concrete slab is 75 mm thick. The maximum size of reinforcement bar that can be used is 8 mm diameter


318. In the design of two-way slab restrained at all edges, torsional reinforcement required is Nil

319. At the time of initial tensioning, the maximum tensile stress in tendon

immediately behind the anchorage shall not exceed. 80% of the ultimate tensile strength of the wire or bar or strand

320. The cable for a prestressed concrete simply supported beam subjected to uniformly distributed load over the entire span should ideally be parabolic with zero eccentricity at the ends and maximum eccentricity at the centre of the span

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