78. The section modulus of a rectangular light beam 25 metres long is 12.500 cm3. The beam is simply supported at its ends and carries a longitudinal axial tensile load of 10 tonnes in addition to a point load of 4 tonnes at the centre. The maximum stress in the bottom most fibre at the mid span section, is

A. 13.33 kg/cm2 tensile

B. 13.33 kg/cm2 compressive

C. 26.67 kg/cm2 tensile

D. 26.67 kg/cm2 compressive

79. The effect of arching a beam, is

A. to reduce the bending moment throughout

B. to increase the bending moment throughout

C. nothing on the bending throughout

D. all the above.

80. A three-hinged arch is said to be :

A. statically determinate structure

B. statically indeterminate structure

C. a bent beam

D. none of these.

81. In a three hinged arch, the bending moment will be zero

A. at right hinge only

B. at left hinge only

C. at both right and left hinges

D. at all the three hinges.

82. In a three hinged arch, the third hinge is generally kept at

A. crown of the arch

B. midpoint of the crown and left support hinge

C. midpoint of the crown and right support hinge

D. none of these.

83. A three hinged arch is loaded with an isolated load 1000 kg at a horizontal distance of 2.5 m from the crown, 1 m above the level of hinges at the supports 10 metres apart. The horizontal thrust is

A. 1250 kg

B. 125 kg

C. 750 kg

D. 2500 kg

84. If a three hinged parabolic arch carries a uniformly distributed load on its entire span, every section of the arch resists.

A. compressive force

B. tensile force

C. shear force

D. bending moment.

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