LOsses in Prestresseec
Jhe abBlied presttess ing o rce does not renain
ConSlant bet decreases uith time.
Nhe amount o force which gets recluced or lost is
Knousn as LOSS OF PRESTRE.SS
tmay vary from 1S to 20%
Types of Losseg-
Short- term locses Long-term losse
Elast1c shortening- Concrete shrinkage
A nchorage slip Concrefe creep
Friction Steel relaxation
Pre-tension ing Past- ension ing-
Elatic defbrmation e Elastc deformation o
Concrete ConCrefe
Reloxahion e stress in Relaxcetion of stress in
Steel steel
Shrinkage Concrete hrinkae of Concrete
4) Cree ot Conciefe Cree Concrete
Ahcherage slib
G) Friction
, LOsS
Elastic delormation of'
Concrefe-
s the tendons are cut ,the stretched tendans tends
to go bock to their
original Stote.
But prevent fromn dang se, by -the irterfacial bond
developed Eefueen the Concrete and tendons.
he Concrele uill be
aubjected to a Compregsive forte,
Which resuts in on instantaneous shortening
the
member.
ince the tendons are bonded to the
concrete, they usill
toss an equal amout et
deformahon, ie ,a reduction
induced skesa.
his is knouon as less due to e lastic deformodtion.
Note-14 all tendons are stresced SIMULTANEOUSLY,
No loce e pestress becauuse the Prestteas qauge
records the opplied stress ater the shortening has
taken place.
Henclons are stressed one by One e SvCCESIVE
A1 Hendons will lase stress due to elatic shotebina
oConcrete Caused by foroes in the sibsequent tendons,
excebt the tast one.
, Loss elue te Relaxation of' sress in Steel -
Hom the time ,the tencons ate anchoted until tronster
Prestressing force.-to the. tonoete, the tendons aie
held between the tloe abutments at a consBat length.
The sttetched tendon
during this time intervas will
lose some its induced atess due to the
phenomenon
Knoun as relaxation esteel.
Loss due to Shrinkage and Cree o Concrete -
ter the ttonsfer ot presregs, concrete keebs on
Shrinking. due to the logs 9 free nlater and
Continues shortening- under Sustaned Stess,
thus resulting in a loss ef tension in the embedded
tendon
hese are Rnown as Lass due to
toss due tor Creeb
shrinkage and
resþectively
so loss due to relax ahion stee) continues
eHer a
long peicd, a Hinal value is reached
Loss due te Anchorage SL
During the process o anchering, the strested tenden
tends te slib belcte the ful gib is establis hel,
thus losing some e i s induced stregg.
hi's i knouon as loss due to anchorage slip.
Jhe abBlied presttess ing o rce does not renain
ConSlant bet decreases uith time.
Nhe amount o force which gets recluced or lost is
Knousn as LOSS OF PRESTRE.SS
tmay vary from 1S to 20%
Types of Losseg-
Short- term locses Long-term losse
Elast1c shortening- Concrete shrinkage
A nchorage slip Concrefe creep
Friction Steel relaxation
Pre-tension ing Past- ension ing-
Elatic defbrmation e Elastc deformation o
Concrete ConCrefe
Reloxahion e stress in Relaxcetion of stress in
Steel steel
Shrinkage Concrete hrinkae of Concrete
4) Cree ot Conciefe Cree Concrete
Ahcherage slib
G) Friction
, LOsS
Elastic delormation of'
Concrefe-
s the tendons are cut ,the stretched tendans tends
to go bock to their
original Stote.
But prevent fromn dang se, by -the irterfacial bond
developed Eefueen the Concrete and tendons.
he Concrele uill be
aubjected to a Compregsive forte,
Which resuts in on instantaneous shortening
the
member.
ince the tendons are bonded to the
concrete, they usill
toss an equal amout et
deformahon, ie ,a reduction
induced skesa.
his is knouon as less due to e lastic deformodtion.
Note-14 all tendons are stresced SIMULTANEOUSLY,
No loce e pestress becauuse the Prestteas qauge
records the opplied stress ater the shortening has
taken place.
Henclons are stressed one by One e SvCCESIVE
A1 Hendons will lase stress due to elatic shotebina
oConcrete Caused by foroes in the sibsequent tendons,
excebt the tast one.
, Loss elue te Relaxation of' sress in Steel -
Hom the time ,the tencons ate anchoted until tronster
Prestressing force.-to the. tonoete, the tendons aie
held between the tloe abutments at a consBat length.
The sttetched tendon
during this time intervas will
lose some its induced atess due to the
phenomenon
Knoun as relaxation esteel.
Loss due to Shrinkage and Cree o Concrete -
ter the ttonsfer ot presregs, concrete keebs on
Shrinking. due to the logs 9 free nlater and
Continues shortening- under Sustaned Stess,
thus resulting in a loss ef tension in the embedded
tendon
hese are Rnown as Lass due to
toss due tor Creeb
shrinkage and
resþectively
so loss due to relax ahion stee) continues
eHer a
long peicd, a Hinal value is reached
Loss due te Anchorage SL
During the process o anchering, the strested tenden
tends te slib belcte the ful gib is establis hel,
thus losing some e i s induced stregg.
hi's i knouon as loss due to anchorage slip.
