s
egligiblea
ddisregardedThisisbecausethete
sileforcesresulti
gfromthebe
di
gmome
tsareresistedbythebo
dcreatedi
therei
forceme
tprocessCracki
ga
ddeflectio
arethereforeesse
tiallyirrecoverablei
rei
forcedco
creteo
cethememberhasitslimitstateatserviceload
Therei
forceme
ti
therei
forcedco
cretememberdoes
otexerta
yforceofitsow
o
thememberco
trarytotheactio
ofprestressi
gsteelThesteelrequiredtoproducetheprestressi
gforcei
theprestressedmemberactivelypreloadsthememberpermitti
garelativelyhighco
trolledrecoveryofcracki
ga
ddeflectio
O
cetheflexuralte
silestre
gthoftheco
creteisexceededtheprestressedmemberstartstoactlikearei
forcedco
creteeleme
t
Prestressedmembersareshalloweri
depththa
theirrei
forcedco
cretecou
terpartsforthesamespa
a
dloadi
gco
ditio
sI
ge
eralthedepthofaprestressedco
cretememberisusuallyabout65to80perce
tofthedepthofthe
fequivale
trei
forcedco
cretememberHe
cetheprestressedmemberrequireslessco
cretea
dabout20to35perce
toftheamou
tofrei
forceme
tU
fortu
atelythissavi
gi
materialweightisbala
cedbythehighercostofthehigherqualitymaterials
eededi
prestressi
gAlsoregardlessofthesystemusedprestressi
goperatio
sthemselvesresulti
a
addedcostFormworkismorecomplexsi
cethegeometryofprestressedsectio
sisusuallycomposedoffla
gedsectio
swiththi
webs
I
spiteoftheseadditio
alcostsifalargee
ough
umberofprecastu
itsarema
ufacturedthediffere
cebetwee
atleastthei
itialcostsofprestresseda
drei
forcedco
cretesystemsisusually
otverylargeA
dthei
directlo
gtermsavi
gsarequitesubsta
tialbecauselessmai
te
a
ceis
eededalo
gerworki
glifeispossibleduetobetterqualityco
troloftheco
cretea
dlighterfou
datio
sareachievedduetothesmallercumulativeweightofthesuperstructure
O
cethebeamspa
ofrei
forcedco
creteexceeds70to90feet213to274mthedeadweightofthebeambecomesexcessiveresulti
gi
heaviermembersa
dco
seque
tlygreaterlo
gtermdeflectio
a
dcracki
gThusforlargerspa
sprestressedco
cretebecomesma
datorysi
cearchesareexpe
sivetoco
structa
ddo
otperformaswellduetotheseverelo
gtermshri
kagea
dcreeptheyu
dergoVerylargespa
ssuchassegme
talbridgesorcablestayedbridgesca
o
lybeco
structedthroughtheuseofpristressi
g
Prestressdco
creteis
ota
ewco
ceptdati
gbackto1872whe
PHJackso
a
e
gi
eerfromCalifor
iapate
tedaprestressi
gsystemthatusedatierodtoco
structbeamsorarchesfromi
dividualblocksseeFigure121aAfteralo
glapseoftimeduri
gwhichlittleprogresswasmadebecauseoftheu
availabilityofhighstre
gthsteeltoovercomeprestresslossesREDillofAlexa
driakNebraskarecog
izedtheeffectoftheshri
r