This set of Prestressed Concrete Structures test focuses on “Restoration of Strength of Structures”.
1. The repair and rehabilitation of damaged or spalled concrete is done by removing the ____________
a) Loose concrete
b) Collapsing
c) Breakage
d) Bonding
View Answer
Explanation: Repair and rehabilitation of damaged or spalled concrete is done by removing the unsound or loose concrete by providing temporary supports to the girder to relieve dead load stresses and the case of pretressed concrete bridge decks, special stress check up is essential before starting the repair works.
2. In many cases of heavily loaded girders, shear distress is observed near the ____________
a) Edges
b) Supports
c) Span
d) Length
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Explanation: In many cases of heavily loaded, girders shear distress is observed near the supports in the form of diagonal tension cracks and shear cracks may arise due to improper detailing or compaction of concrete near the support zone in such cases holes are drilled diagonally and rebars are placed and grouted to arrest the shear cracks.
3. Bridge girders located in zones of very severe exposure conditions suffer ____________
a) Spalling
b) Bleeding
c) Winding
d) Spinning
View Answer
Explanation: Bridge girders located in zones of very severe exposure conditions are like it to suffer: Spalling extensive spalling of concrete exposing the reinforcements and in such cases the unsound or loose concrete around the girders is removed and repairing against the loss of concrete section is done by jacketing the girders using a steel form.
4. The crack propagation in the concrete girders can be arrested by using the principles of ____________
a) Pre tensioning
b) Post tensioning
c) Prestressing
d) Loading
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Explanation: Crack propagation in the concrete girders can be arrested by using the principles of post tensioning and in this tensile cracking in the girder are arrested by including compression using tension ties forced to the sides of the girder at locations of tensile cracks.
5. In some cases of repairs of girders damaged by collision, the damage is severe what is used?
a) Trusses and bars
b) Struts and pins
c) Links and dowels
d) Lace and anchores
View Answer
Explanation: In some cases, the damage is more severe deeper so that the high tensile wires and strands are exposed and in such cases, the damaged portion is repaired by using links ad dowels along with wire mesh tied to the reinforcements and the entire damaged part is repaired using mortar or non shrink grout.
6. The corrosion of reinforcement due to extreme exposure is common for structure located in ____________
a) Dry conditions
b) Costal zones
c) Regional zones
d) Hot condition
View Answer
Explanation: Due to various reasons such as corrosion of reinforcements due to extreme exposure conditions, especially when un bonded tendons are used, the high tensile strands may get damaged resulting in loss of prestresss in the girder.
7. In case of damaged prestressed concrete I girders which are used for restoring strength?
a) Pretensioning
b) Post tensioning
c) Chemicals
d) Dies
View Answer
Explanation: Post tensioning rods (one on either side of the web) in conjugation with jacking (concrete) corbels located outside the damaged areas can be used to restore the strength of the prestressed girder and to start with the calculated preload is applied and the damaged concrete is repaired.
8. In restoration of strength by adding external reinforced concrete the damages concrete is first repaired by applying ____________
a) Preload
b) Tensile load
c) Compressive load
d) Overload
View Answer
Explanation: In this method, the damaged concrete is first repaired by applying the required preload and the concrete a corbels are constructed with the required conventional steel reinforcement and it shows adding external reinforcement concrete to restore the strength of the damaged girder.
9. In method 3 the restoration is done y addition of ____________
a) Metal sleeve jacket
b) Aluminium jacket
c) Steel jacket
d) Water proof jacket
View Answer
Explanation: In this methods preload is applied prior to the repair of the damaged concrete and removed after the completion of repairs and a metal sleeve jacket is installed around and beyond the damaged area and the gap between the metal sleeve girders is filles with epoxy grout by pressure injection.
10. The depth of structural element is increased by adding ____________
a) Excess concrete
b) Low concrete
c) Prestressed concrete
d) Dies
View Answer
Explanation: The depth of structural elements is increased by adding an new layer of concrete on top of an existing cross sections and bonding the old and new elements with modern epoxy resin adhesives and the total reinforcement in the cross section is increased by epoxy bonding of thin steel plates on the tension face of the beam to increase the flexural and shear strength.
Sanfoundry Global Education & Learning Series – Prestressed Concrete Structures.
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