250+ TOP MCQs on Strengthening Structures of Externally Bonded Plates and Answers

Prestressed Concrete Structures Questions and Answers for Experienced people on “Strengthening Structures of Externally Bonded Plates”.

1. The restoration of structures by rectifying constructional deficiencies are as a result of ____________
a) Cross section
b) Span
c) Dimensioning
d) Slab
Answer: c
Clarification: The range of application of this strengthening technique is ideally suited for the following situations: restoration of structures by rectifying constructional deficiencies that impair the safety of the structure as a result of faulty dimensioning, corrosion of reinforcement, insufficient reinforcement, overloading etc.

2. The first attempt to strengthen concrete flexural elements by externally bonded steel plates was attempted in?
a) Germany
b) France
c) America
d) Russia
Answer: b
Clarification: The first reported attempts to strengthen concrete flexural elements by externally bonded steel plates were attempted in France around 1964-65 and practical applications date back to 1966-67 in France and South Africa followed by Japan and Russia.

3. The load bearing capacity of a structural element can be increased by changing ____________
a) Foundation
b) Design
c) Span
d) Loads
Answer: c
Clarification: The strengthening of an existing structural element by increasing its load bearing capacity and altering the load supporting system by changing spans by shifting or removing of supports, conversion of continuous beam to single span beam and vice versa etc.

4. In Switzerland the externally bonded steel plates were used for ____________
a) Bridges
b) Crops
c) Dams
d) Tanks
Answer: a
Clarification: In Switzerland this method has been extensively used in both buildings and bridges and experiments conducted have shown that reinforced concrete beams, when epoxy bonded with steel plates on the tension face it exhibits significant increase up to 3% in the ultimate flexural strength in comparison with non plated beams.

5. Which grade of structural steel is suitable for bonded reinforcing plates?
a) M25
b) M35
c) Any grade
d) M10
Answer: c
Clarification: Generally any grade of structural steel is suitable for bonded reinforcing plates and plate gauges below 3mm are not suitable because sand blasting can deform them and steel plates between 6-16mm thick were used in some strengthening works.

6. The pretreatment of concrete surface is generally carried out by ____________
a) Sand blasting
b) Forrowing
c) Bleeding
d) Blasting
Answer: a
Clarification: Pretreatment of the concrete surface is generally carried out by sand blasting, shotcrete blasting, grinding or roughening with pneumatic needle gun or granulating hammer and the grain structure of the concrete must be exposed before the steel plates are fixed.

7. The tensile shear strength of the adhesive is initially proportional to the square root of ____________
a) Span
b) Thickness
c) Area
d) Eccentricity
Answer: b
Clarification: The adhesive joint is generally between 1-3mm thick and tests have shown that the tensile shear strength of the adhesive is initially proportional to the square root of the thickness however the tensile shear strength reaches a maximum and then starts decreasing as the adhesive thickness is further increased and hence the thinner layers prove stronger and have greater resistance than thick ones.

8. The repair procedure in severe damage includes ____________
a) Grouting
b) Collapse
c) Shortcrete
d) Mud
Answer: c
Clarification: The detailed examination of the damage and review of calculations will help in selecting a cost effective and appropriate restoration technique for the damaged structure and the loss of prestress is excessive resulting in tensile cracks, preloading method should be seriously considered in making concrete repairs in order to restore the equivalent full or partial prestresss effect, as per original designs and the repair procedure may also include epoxy resin pressure injection, Shortcrete and additional welded fabric with drilled anchors and guniting.

9. Before patching the exposure strands should be coated with ____________
a) Thick cement grout
b) Slurry cement grout
c) Hardened cement grout
d) Watery cement grout
Answer: b
Clarification: In moderate damage it is recommended that welded wire fabrics be attached to drilled dowels placed at about 500mm spacing or to the existing reinforcement in the damaged area and if the prestressing strands are exposed, sufficient care must be taken so as not to damage the steel during the cleaning operation and the exposed strands should be coated with epoxy resin bonding compound or slurry cement grout before patching.

10. Elastomers have excellent adhesion to concrete and are not susceptible to ____________
a) Hardening
b) Shaving
c) Collapsing
d) Softening
Answer: d
Clarification: Elastomers have excellent adhesion to concrete and are not suspectable to softening within the normal range of ambient temperatures and normally Elastomers exhibit a higher degree of elongation of as much as 10 percent extension but in practice, this should be limited to 50 percent and the groove depth to width ratio should be 1.2, the material should be prevented from adhering to the bottom so that the crack remains free as a live crack.

Prestressed Concrete Structures for Experienced people,