LEC 1.4 Flashcards
Advantages of PC
The modulus of rupture significantly increased ( __ Mr in RC and ___Mr in Plain)
2, 9=7.5
The prestressed member depth is ____ to ___ % of the depth of equiv. RC
65 , 80
Prestressed concrete requires less concrete and about ___ to ___ % of the amount of reinforcement
20, 35
The limitations of PC is that prestressing needs skilled _______________.
technology
This is fabricated in factories, mass production, economical, controlled condition, “long-line” system
Pre tensionsioning
the construction process of this is that it lays ducts in the correct position of concrete
Post tensioning
suitable for in situ construction
post tensioning
complete elimination of tensile stresses in members at normal service load
full prestressing
at reduced load, have large camber/negative deflection
full prestressing
some flexural cracking is permitted at full service load
partial prestressing
at reduced load, crack would be small/closed completely
partial prestressing
this utilized additional ordinary reinforcing bars in tension zone
partial prestressing
it stresses the tendons to less than their full permitted value
partial prestressing
when the prestressing tendons are parallel to one axis
uniaxial prestressing
when there are prestressing tendons parallelto two axes
biaxial prestressing
when there are prestressing tendons parallel to more than two axes
multi axial prestressing
Pre tensioning is suitable for __________ members produced in bulk
pre tensioning
In _____________ large anchorage device is not present
pre tensioning
The waiting period in the casting bed is less
post tensioning
This is suitabl for heavy cast-in place members
post tensioning
The relative disadvantage of post tensioning as compared to pre tensioning is the requirement of _____________ device and _________ equipment
anchorage, grouting
In post tensioned members the ____________________ transfer the prestress to the concrete.
anchoring devices
ANCHORING DEVICES
It consists of an anchorage block and wedges. The strands are held by frictional grip of the wedges in the anchorage block.
wedge action
The examples of wedge action are
Freyssinet, Glifford - Udall, Anderson and Magnel Blaton
