3. *Temperature variations and shrinkage are the
most important causes of structure deformation
*It causes deflection,cracks,and creeps in
concrete
4. • Change of pore water content due to temperature
variations like drying process causes volume
changes in structure ,this phenomenon is called
shrinkage
• In shrinkage mainly loss of water consumed by
hydration reaction
• change in volume during hardening resulting
shrinkage stress
5. • Rapidly drop of temperature
between day and night can
cause contraction in a
concrete length ie. shrinkage ,
which is sufficient to causing
cracking
• Crack produce when tensile
stress>concrete tensile stress
6. As concrete weak in
tension ,the resulting stress
of shrinkage produce
cracks known as hairline
cracks
• This cracking decreased
load carrying capacity
7. • Reducing strength with time
under constant stress and
temperature known as creep
• At high temperature atoms are
dislocated,which causes creep
deformation
• It is a tendency of a solid
material deform permanently
under the influence of stress
,which is generated by
temperature effect
8. • This deformation is function of
exposure time and exposure
temperature
• Moisture content available in
creep
• if the stress is applied long
enough, the material may
gradually deform until it breaks
9. • In prestress design temperature and shrinkage effect known
as loss
• Creep loss and shrinkage loss are the example of them
• To get the accurate effective prestress this loss should be
calculated
• Effective Prestress= Initial Prestressing Force - All Losses
• Loss due to creep: ∆fc=(Cc-1)n fc N/mm²
, Cc=coefficient of creep
• Loss due to shrinkage: ∆fc=Es s
N/mm² , s=coefficient of shrinkage
10. *Distribution reinforcement reducing this
effect
*When concrete tends to shrinkage such
reinforcement resist the contraction
*If crack prodused will be smaller width
and more evenly distributed to the
concrete
*This reinforcement provided
perpendicular to the main reinforcement
bar,used in one way slab
11. *This reinforcement
requires in floor and roof
slab
*using high paste concrete
with proper amount of
water and cement reduce
this effect
12. Temparature and shrinkage
effect can be minimize but it can
not be remove permanently so,
proper admixtures,appropriate
ratios must be taken for reducing
this effects.Adequate building
codes with balanced design can
provide safe building.
