PC LOSSES

Question 1

This reduction in force is referred to as _________and is addressed as part of the design of a prestressed member.

Answer 1

partial prestress loss

Question 2

The following loss mechanisms have historically been listed by the code for consideration:

Answer 2

(a) Prestressed reinforcement seating at transfer (initial)
(b) Elastic shortening of concrete (initial)
(c) Creep of concrete (long-term)
(d) Shrinkage of concrete (long-term)
(e) Relaxation of prestressed reinforcement (long-term)
(f) Friction loss due to intended or unintended curvature in post-tensioning tendons
(initial)

Question 3

reinforcement stress changes may be calculated as the stress in the concrete times the _____

Answer 3

modular ratio n

Question 4

Methods available for this task vary in complexity and accuracy. In general, the methods are categorized as follows:

Answer 4

1. Lump sum
2. Detailed
3. Time-dependent

Question 5

For decades engineers have used_________, the total combined losses in the prestress based on experience or historical data, to select the initial prestress.

Answer 5

lump sum losses

Question 6

Pretensioning losses
Post-tensioning losses

Answer 6

35 ksi
25 ksi

Question 7

When a prestressing tendon is released from the jack, there is a small amount of movement, or ______

Answer 7

set

Question 8

the total loss due to
friction is the sum of ____due to misalignment and ________ due to the intentional curvature resulting from the alignment the duct in the member

Answer 8

wobble friction
curvature friction

Question 9

________ are assumed to be constant along the duct and present even in nominally straight ducts.

Answer 9

Wobble friction values k

Question 10

_______ is a function of the angle of curvature α intentionally designed into the duct placement and the coefficient of friction μ between the tendon and the duct with a total effect equal to μα.

Answer 10

Curvature friction

Question 11

The corresponding stress
loss is calculated

Answer 11

at the level of the tendon