Prestressed Concrete Structures Multiple Choice Questions on “Deflections of Composite Members”.
1. In the case of composite members, deflections are computed by taking into account the different stages of ___________
a) Tension
b) Loading
c) Ranging
d) Hogging
Answer: b
Clarification: In the case of composite members, deflections are computed by taking into account the different stages of loading as well as the differences in the modulus of elasticity of concrete in the precast prestressed unit and then insitu cast element.
2. The initial deflection is due to ___________
a) Self weight
b) Cross section
c) Beam weight
d) Foundation
Answer: a
Clarification: The initial deflection due to prestress of self weight of the beam and the weight of the insitu cast concrete if the beam is not propped is computed on the basis of the section and the modulus of elasticity of the precast unit.
3. The live load deflection is always estimated using ___________
a) Beam sections
b) Composite sections
c) Bent sections
d) Rolled sections
Answer: b
Clarification: The live load deflection is always estimated using composite properties if the precast beam is propped during construction and the deflections due to dead weight of in situ concrete is also computed on the basis of composite sections.
4. When the modulus of elasticity of the precast and insitu cast concrete are different the flexural rigidity is worked out by?
a) First moment of area
b) Second moment of area
c) Limit states
d) Composite beam
Answer: b
Clarification: When the modulus of elasticity of the precast and insitu cast concrete are different the flexural rigidity is worked out by computing the equivalent second moment of area of the composite sections using the modular ratio and the deflections computed under service loads should not exceed the limiting values prescribed in the codes.
5. One of the knowledge required for planning of any structural component is ___________
a) Seismic nature of terrain
b) Regional nature of terrain
c) Wind nature of terrain
d) Loads
Answer: a
Clarification: Planning of any structure like a building, bridge, marine structures or storage structures requires comprehensive knowledge of the various parameters like site conditions availability of skilled labour and materials, transportation facilities, seismic nature of the terrain, sub soil water conditions, choice of material like steel, reinforced or prestressed concrete, weather and durability considerations, clients requirements and the funds earmarked for the structures.
6. In general appropriate technology must necessarily involve the prevailing?
a) Structures
b) Infastructure
c) Codes
d) Books
Answer: b
Clarification: In general, appropriate technology must necessarily involve the prevailing local infrastructure like raw materials, man power, plant and machinery, power and financial resources and an excellent example of appropriate technology can be found in the low cost suspension bridges built by Girish bharadwaj in south India.
7. The factors which influence the cost of a bridge are ___________
a) Method of erection
b) Length of beam
c) Cost of water
d) Testing of materials