This set of Prestressed Concrete Structures online quiz focuses on “Effects of Indeterminate structures”.
1. The ultimate load capacity is higher in case of:
a) Statically indeterminate structures
b) Statically determinate structures
c) Prestressed structures
d) Reinforced structures
Explanation: The ultimate load carrying capacity is higher than in statically indeterminate structures than in determinate structure due to the phenomenon of redistribution of moments, reduction in the size of member’s results in lighter structures.
2. The bending moments are more evenly distributed between:
a) Ends and supports
b) Centre and supports
c) Edge and supports
d) Surface and supports
Explanation: The bending moments are more evenly distributed between the centre of span and the supports of member’s leads to increased stability and in continuous prestresssed structures, the deflections are comparatively small as compared to simply supported span.
3. In continuous post tensioned girders the curved cables can be positioned to resist:
a) Edge and supports
b) Beam and supports
c) Span and supports
d) Columns and supports
Explanation: In continuous post tensioned girders, the curved cables can be suitably positioned to resist the span and support moments, continuity of the members in framed structures leads to increase stability, in framed structures leads to increase stability continuous girders are formed by segmental construction using precast units connected by prestressed cables.
4. There is a reduction of anchorage in case of:
a) Precast prestressed beam
b) Pre tensioned prestressed beam
c) Continuous prestressed
d) Partially prestressed
Explanation: A reduction in the number of anchorages in a continuous prestressed beam in comparison with a series of simply supported beam only one pair of post tensioning anchorages and a single stressing operation can serve several members.
5. When an indeterminate structure is prestressed which reactions develop?
Explanation: When an indeterminate structure is prestressed, reductant reactions will develop due to the redundancies exercising a restraint at the supports and the redundant reactions which develop as a consequence of prestressing an indeterminate structure result in secondary moments.
6. Which type of structure is free to deform?
a) Statically determinate
b) Continuous structure
c) Statically indeterminate
d) Partially prestressed structure
Explanation: While a statically determinate structure is free to deform when prestressed a continuous structure cannot deform freely and however the deflections should conform to the law of consistent deformation.
7. The formation of redundant reactions is examined with reference to:
a) One span continuous beam
b) Two span continuous beam
c) Three span continuous beam
d) Four span continuous beam
Explanation: The formation of redundant reactions and secondary moments are examined with reference to a two span continuous beam, prestressed by a straight cable local at a uniform eccentricity throughout the span.
8. The problem of excessive frictional losses can be tackled by reducing:
b) Prestressing force
Explanation: The problem of excessive frictional losses can be tackles by reducing the curvature of the cables housed in members of variable depth and also by temporarily overstressing the tendons from both ends.
9. The stresses due to secondary moments can be eliminated by selecting suitable:
a) Cable profile
b) Tendon profile
c) Anchorage profile
d) Wedge profile
Explanation: Stresses due to secondary moments can be eliminated by selecting suitable tendon profile which do not induce secondary moments and it is also possible to provide for secondary stresses in the design and if under reinforced sections are used, the redistribution of moments will be more or less complete resulting in higher collapse loads and these loads could be estimated by suing the well established plastic theory as applied to structural steel members.
10. The computation of collapse or ultimate load is influenced by:
a) Degree of compression
b) Degree of bending
c) Degree of redistribution
d) Degree of strain
Explanation: The computation of collapse or ultimate load is influenced by the degree of redistribution of moments in the continuous structure cables positioned to cater for secondary moments are not generally suitable to provide the required ultimate moment under a given system of loads.
Sanfoundry Global Education & Learning Series – Prestressed Concrete Structures.
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