F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

358 Prestressed concrete simple beams
1600
1400
11200
E
~1000
en
en
~ 800
-en
c
.g 600
c
I
.2!.
400
200 I
I
"
v
\ ~ r-:
~= 8-969
I (,pb: 8·969 I
Epb+0·0035
fpb-0·001329
I -
{ E 5 =200kN/mm 2 -
I J
0•002 0•004 0•006 0•008 0•010 0•012 0·014
Tendon strain
Fig. 9.5-3 Tendon stress/strain curve
Concrete stress at tendon level
_ 3.003 X 10 6 + 3.003 X 10 6 X 270 2 = 10.06 N/mm2
- 4.8 X 105 5.76 X 1010
Concrete prestrain at tendon level, Ee,
10.06
= 36 X 10 3 = 0.000279
Concrete strain Eu at tendon level at collapse
= 870 X- X X 0.0035 = e·~ 45 - 0.0035)
Change in tendon strain due to ultimate moment, Epa'
= change in concrete strain, Ee + Eu
= 0.000279 + 3·045 - 0.0035 = 3·045 - 0.003221
X . X
Tendon prestrain = 200 9 ~ 0 103 = 0.00455
Therefore, tendon strain Epb at collapse is given by
fpb = 0.00455 + 3 ·~ 45 - 0.003221