A4.2—Design example: Using post-tensioning to
minimize cracking
Assume P-T strip 500 x 12 ft.
Determine minimum residual (effective) compression
after all losses.
Calculate P-T requirement for minimum residual
compression (P/A), assume 250 psi:
Assume slab thickness: 6 in.
Calculate P-T requirement to overcome the subgrade friction
using
Eq. (9-1)
:
Assume subgrade friction factor: 0.5
L
( )
0.07
d
( )
0.40
P
( )
0.03
e
m
( )
0.16
Y
m
( )
0.67
3.0 S
( )
0.015
--------------------------------------------------------------------------------------
120
(
)
0.07
26
( )
0.40
2280
(
)
0.03
5.0
(
)
0.16
0.338
(
)
0.67
3.0 14.50
(
)
0.015
---------------------------------------------------------------------------------------------------------------
f
c
′
3000
VW
ndb
---------
1.300
(
) 58
( ) 1000
(
)
5
( ) 12
( ) 26
( )
----------------------------------------------
=
58
( )
0.07
26
( )
0.40
2280
(
)
0.03
5.0
(
)
0.16
0.338
(
)
0.67
3.0 15
( )
0.015
------------------------------------------------------------------------------------------------------------
1.235
(
) 120
(
) 1000
(
)
9
( ) 12
( ) 26
( )
-------------------------------------------------
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