155. If R and 7' are rise and tread of a stair spanning horizontally, the steps are supported by a wall on one side and by a stringer beam on the other side, the steps are designed as beams of width
A. R + T
B.R*T
C. R - T .
D. none of these.

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156.  For stairs spanning horizontally, the minimum waist provided is
A. 4 cm
B. 6 cm
C. 8 cm
D. 12 cm.

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157. The number of treads in a flight is equal to
A. risers in the flight
B. risers plus one
C. risers minus one
D. none of these.

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158.  A pre-stressed concrete member
A. is made of concrete
B. is made of reinforced concrete
C. is stressed after casting
D. possesses internal stresses.

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159.  In favourable circumstances a 15 cm concrete cube after 28 days, attains a maximum crushing strength
A. 100 kg/cm2
B. 200 kg/cm2
C. 300 kg/cm2
D. 400 kg/cm2

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160. A pre-stressed concrete member is preferred because
A. its dimensions are not decided from the diagonal tensile stress
B. large size of long beams carrying large shear force need not be adopted
C. removal of cracks in the members due to shrinkage
D. all the above.

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161.  In a prestressed member it is advisable to use
A. low strength concrete only
B. high strength concrete only
C. low strength concrete but high tensile steel
D. high strength concrete and high tensile steel

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