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PRCD FINAL TERMS > Prestressed > Flashcards

Prestressed Flashcards

1
Q

A _________ structure is different from a
conventional reinforced concrete structure due to the
application of an initial load on the structure prior to its
use.

A

prestressed concrete

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2
Q

The _______ or ‘prestress’ is applied to enable the
structure to counteract the stresses arising during its
service period.

A

initial load

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3
Q

tensile strength of concrete is only about ___ to ____ of its compressive strength

A

8% to 14%

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4
Q

cracks tend to develop at _________ of loading in flexural members such as beams and slabs

A

early stages

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5
Q

to prevent cracks, _________ can be suitably applied in the perpendicular direction

A

compressive force

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6
Q

_________ enhance the bending, shear, and torsional capacities of the flexural members

A

Prestressing

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7
Q

In ____ and ______ tanks, the hoop tensile stresses can be effectively counteracted by circular prestressing

A

pipes, liquid storage

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8
Q

It was observed that the effect of prestress
reduced with ______

A

time

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9
Q

The ________ of the members
were limited.

A

load resisting capacities

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10
Q

Under ________, the members were
found to fail

A

sustained loads

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11
Q

Under sustained load, the strain in concrete
increases with increase in time. This is known
as ________

A

creep strain

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12
Q

The reduction in length due to creep and
shrinkage is also applicable to the _______, resulting in significant loss in the tensile
strain.

A

embedded
steel

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13
Q

The total loss in strain due to elastic shortening, creep and shrinkage was also close to _______

A

0.0007

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14
Q

Obtained a patent for the manufacture of Portland
cement

A

1824 Aspdin, J

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15
Q

Introduced steel wires in concrete to make flower pots,
pipes, arches and slabs.

A

1857 Monier, J

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16
Q

Introduced the concept of tightening steel tie
rods in artificial stone and concrete arches.

A

1886 Jackson, P.H.

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17
Q

Manufactured concrete slabs and small beams with embedded
tensioned steel

A

Doehring, C.E., (Germany)

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18
Q

Recognized losses due to
shrinkage and creep, and suggested retightening
the rods to recover lost prestress.

A

1908 Stainer, C.R

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19
Q

Developed a method of winding
and pretensioning high tensile steel wires around
concrete pipes.

A

1923 Emperger, F.

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20
Q

Hoop-stressed horizontal
reinforcement around walls of concrete tanks through the
use of turnbuckles.

A

1924 Hewett, W.H.

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21
Q

Used high strength unbonded steel rods. The rods
were tensioned and anchored after hardening of the concrete

A

1925 Dill, R.H

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22
Q

Used high tensile steel wires, with ultimate strength as high as 1725
MPa and yield stress over 1240 MPa. In 1939, he developed conical
wedges for end anchorages for post-tensioning and developed
double-acting jacks

A

1926 Eugene Freyssinet (France)

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23
Q

Developed ‘long line’ pre-tensioning
method.

A

1938 Hoyer, E

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24
Q

Developed an anchoring system for
post-tensioning, using flat wedges

A

1940 Magnel, G.

25
Q

_______ is a single unit made of steel

A

Prestressing Wire

26
Q

two, three, or seven wires are wound to form a ________

A

Prestressing strand

27
Q

a group of strands or wires are wound to form a ________-

A

Prestressing tendon

28
Q

A ground of tendons for a ______

A

prestressing cable

29
Q

a ______ can be made up of a single steel bar

A

tendon

30
Q

when there is adequate bond between the prestressing tendon and concrete, it is called ___________-

A

bonded tendon

31
Q

__________ and _________ tendons are bonded tendons

A

Pre-tensioned, grouted post-tensioned

32
Q

when there in no bond between the prestressing tendon and concrete, it is called _________

A

unbonded tendon

33
Q

when _____ is not applied after post-tensioning, the tendon is an unbonded tendon

A

grout

34
Q

Stages of loading

A

initial
Intermediate
Final

35
Q

Span to depth ratio for non-prestressed slab

A

28:1

36
Q

Span to depth ratio for prestressed slab

A

45:1

37
Q

In the Philippines, the application of prestressed concrete
diversified over the years. Among bridges, the __________ in
Bukidnon, Philippines remains a classic example of prestressed

A

Atugan Bridge

38
Q

Prestressing needs __________

A

skilled technology

39
Q

Types of prestressing

A

Hydraulic
Mechanical
Electrical
Chemical

40
Q

This classification is based on the location of the prestressing tendon with respect to the
concrete section.

A

External or internal prestressing

41
Q

This is the most important classification and is based on the sequence of casting the
concrete and applying tension to the tendons.

A

Pre-tensioning or post-tensioning

42
Q

This classification is based on the shape of the member prestressed.

A

Linear or circular prestressing

43
Q

Based on the amount of prestressing force, three types of prestressing are defined.

A

Full, limited or partial prestressing

44
Q

As the names suggest, the classification is based on the directions of prestressing a
member.

A

Uniaxial, biaxial or multi-axial prestressing

45
Q

The _______ is transferred to the concrete from the tendons, due to the bond between them.

A

prestress

46
Q

The various stages of the pre-tensioning operation are summarized as follows.

A

1)Anchoring of tendons against the end abutments
2) Placing of jacks
3) Applying tension to the tendons
4) Casting of concrete
5) Cutting of the tendons.

47
Q

is suitable for precast members produced in bulk

A

Pre-tensioning

48
Q

___________ is required for the pre-tensioning operation.

A

prestressing bed

49
Q

There should be good bond between concrete and steel over the ____________

A

transmission length

50
Q

_________ is suitable for heavy cast-in-place members.

A

Post-tensioning

51
Q

the relative disadvantage of post-tensioning as compared to pre-tensioning is the requirement of ___________ and ___________

A

anchorage device, grouting equipment.

52
Q

In post-tensioned members the ___________ transfer the prestress to the concrete.

A

anchoring devices

53
Q

principles of anchoring the tendons.

A

1) Wedge action
2) Direct bearing
3) Looping the wires

54
Q

The_________ based on wedge action consists of an anchorage block and
wedges. The strands are held by __________ of the wedges in the anchorage block.

A

anchoring device, frictional grip

55
Q

_________ or _________ or ________ formed at the end of the wires directly bear
against a block.

A

rivet or bolt heads or button heads

56
Q

The _______, Leoba system and also the Dwidag single-bar anchorage bo
system, work on this principle where the wires are looped around the concrete. The
wires are looped to make a bulb.

A

Baur-Leonhardt system

57
Q

The _________ are used to connect strands or bars. They are located at the junction of
the members, for example at or near columns in post-tensioned slabs, on piers in posttensioned bridge decks.

A

couplers

58
Q

_________ can be defined as the filling of duct, with a material that provides an anticorrosive alkaline environment to the prestressing steel and also a strong bond between
the tendon and the surrounding grout

A

Grouting

PRCD FINAL TERMS (3 decks)

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