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PCE 3 > MIDTERM > Flashcards

MIDTERM Flashcards

1
Q

Can be found in the same way as that of a reinforced concrete

A

Ultimate Moment of Resistance

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2
Q

The steel is strained in order to produced the prestressed force

A

Ultimate Moment of Resistance

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3
Q

The steel strain should be taken as that due to bending plus that due to prestress force after loss

A

Ultimate Moment of Resistance

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4
Q

Formula for Ultimate Moment of Resistance

A

Mu = fpb · Aps · (d-dn)

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5
Q

For a rectangular beam, or a flanged beam in which the flange thickness is not less than

A

0.9x

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6
Q

If d>0.9x

dn is?

A

0.45x

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7
Q

What are the several causes of contraction of steel wires effecting the reduction (loss) in the prestressed concrete beam

A
  1. Pre-tensioning
  2. Post-tensioning
  3. Loss due to elastic deformation
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8
Q

It undergoes a gradual reduction with time from the stages of transfer due to various causes

A

Initial prestressing

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9
Q

The force which is used to stretch the wire to the required length must be available all the time as prestressing force is the steel is to be prevented from?

A

Contracting

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10
Q

Can be seen during the process of anchoring (loss in prestress)

A

Pretensioning

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11
Q

The stressed tendon tends to slip before the full grip is established, thus losing some of its imposed strain (induced stress)

A

Loss due to anchorage draw-in

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12
Q

From the time the tendons are anchored until transfer of prestressing force to the concrete, the tendons are held between the two abutments at a constant length

A

Pretensioning

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13
Q

The stretch tendons during this time interval will lose some of its induced stress due to phenomenon known as

A

Relaxation of Steel

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14
Q

As soon as the tendons are cut, the stretched tendons tends to go back to their original state, but are prevented from doing so by the interfacial bond developed between

A

The concrete and the tendons

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15
Q

The tendons are located inside ducts, and the hydraulic jacks held directly against the member

A

Post-tensioning

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16
Q

Can be seen during the stressing operation of tendons (loss in prestress)

A

Post-tensioning

17
Q

During stressing operation, the tendons tend to get straightened and slide against duct, thus resulting in the development of

A

Frictional Resistance

18
Q

The stress in the tendon at a distance away from the jacking end will be smaller than that indicated by the pressure gauge mounted on the jack known as

A

loss due to friction

19
Q

The loss of prestress due to deformation of concrete depends on the modular ratio and the average stress in concrete at the level of steel

A

Loss due to elastic deformation

20
Q

Prestress in concrete at the level of steel symbol

A

fc

21
Q

Modulus of elasticity of steel symbol

A

Es

22
Q

Modulus of elasticity of conrete symbol

A

Ec

23
Q

Modular Ratio

A

Le

24
Q

Formula of
Strain in concrete at the level of steel

A

fc / Ec

25
Q

Formula of
Stress in steel corresponding to this strain

A

(fc / Ec) · Es

26
Q

Formula of
Elastic Deformation of Concrete

A

Le · fc

27
Q

Formula pf
Loss of stress in steel

A

Le · fc

28
Q

Results in shortening of tensioned wires and hence contributes to the loss of stress

A

Loss due to shrinkage

29
Q

Is influenced by the type of cement, aggregate and the method of curing used

A

Shrinkage of concrete

30
Q

Use of high strength concrete with low water cement ratio results in ______ and consequent loss of prestress

A

Reduction in shrinkage

31
Q

Progressive loss of water from concrete is its primary cause

A

Drying shrinkage

32
Q

Is higher at the surface of the member

A

The rate of shrinkage

33
Q

____ between the interior surface of large member may result in strain gradients leading to surface cracking

A

The differential shrinkage

34
Q

Is essential to prevent cracks due to shrinkage in prestress members

A

Propoer curing

35
Q

Moist curing is restored in order to prevent shrinkage until the time of transfer

A

Pretensioned members

36
Q

The total residual shrinkage strain will be larger in pretensioned members after transfer of stress is a recommendation made by code

A

IS:1343

37
Q

Total residual shrinkage symbol

A

εcs

38
Q

The loss of stress in steel due to creep of concrete can be estimated if the magnitude of ultimate creep strain or creep-coefficient is known

A

Loss due to creep

PCE 3 (3 decks)

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