Prestressed

Question 1

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.

Answer 1

prestressed concrete

Question 2

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

Answer 2

initial load

Question 3

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

Answer 3

8% to 14%

Question 4

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

Answer 4

early stages

Question 5

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

Answer 5

compressive force

Question 6

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

Answer 6

Prestressing

Question 7

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

Answer 7

pipes, liquid storage

Question 8

It was observed that the effect of prestress
reduced with ______

Answer 8

time

Question 9

The ________ of the members
were limited.

Answer 9

load resisting capacities

Question 10

Under ________, the members were
found to fail

Answer 10

sustained loads

Question 11

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

Answer 11

creep strain

Question 12

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

Answer 12

embedded
steel

Question 13

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

Answer 13

0.0007

Question 14

Obtained a patent for the manufacture of Portland
cement

Answer 14

1824 Aspdin, J

Question 15

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

Answer 15

1857 Monier, J

Question 16

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

Answer 16

1886 Jackson, P.H.

Question 17

Manufactured concrete slabs and small beams with embedded
tensioned steel

Answer 17

Doehring, C.E., (Germany)

Question 18

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

Answer 18

1908 Stainer, C.R

Question 19

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

Answer 19

1923 Emperger, F.

Question 20

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

Answer 20

1924 Hewett, W.H.

Question 21

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

Answer 21

1925 Dill, R.H

Question 22

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

Answer 22

1926 Eugene Freyssinet (France)

Question 23

Developed ‘long line’ pre-tensioning
method.

Answer 23

1938 Hoyer, E

Question 24

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

Answer 24

1940 Magnel, G.

Question 25

_______ is a single unit made of steel

Answer 25

Prestressing Wire

Question 26

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

Answer 26

Prestressing strand

Question 27

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

Answer 27

Prestressing tendon

Question 28

A ground of tendons for a ______

Answer 28

prestressing cable

Question 29

a ______ can be made up of a single steel bar

Answer 29

tendon

Question 30

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

Answer 30

bonded tendon

Question 31

__________ and _________ tendons are bonded tendons

Answer 31

Pre-tensioned, grouted post-tensioned

Question 32

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

Answer 32

unbonded tendon

Question 33

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

Answer 33

grout

Question 34

Stages of loading

Answer 34

initial Intermediate Final

Question 35

Span to depth ratio for non-prestressed slab

Answer 35

28:1

Question 36

Span to depth ratio for prestressed slab

Answer 36

45:1

Question 37

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

Answer 37

Atugan Bridge

Question 38

Prestressing needs __________

Answer 38

skilled technology

Question 39

Types of prestressing

Answer 39

Hydraulic Mechanical Electrical Chemical

Question 40

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

Answer 40

External or internal prestressing

Question 41

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

Answer 41

Pre-tensioning or post-tensioning

Question 42

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

Answer 42

Linear or circular prestressing

Question 43

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

Answer 43

Full, limited or partial prestressing

Question 44

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

Answer 44

Uniaxial, biaxial or multi-axial prestressing

Question 45

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

Answer 45

prestress

Question 46

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

Answer 46

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.

Question 47

is suitable for precast members produced in bulk

Answer 47

Pre-tensioning

Question 48

___________ is required for the pre-tensioning operation.

Answer 48

prestressing bed

Question 49

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

Answer 49

transmission length

Question 50

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

Answer 50

Post-tensioning

Question 51

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

Answer 51

anchorage device, grouting equipment.

Question 52

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

Answer 52

anchoring devices

Question 53

principles of anchoring the tendons.

Answer 53

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

Question 54

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

Answer 54

anchoring device, frictional grip

Question 55

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

Answer 55

rivet or bolt heads or button heads

Question 56

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.

Answer 56

Baur-Leonhardt system

Question 57

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.

Answer 57

couplers

Question 58

_________ 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

Answer 58

Grouting