Nonlinear Finite Element Analysis of Concrete Structures

- 138 -
600
500 -
4.00
0A-2
experimental
faiure load- "
A-2
i—'—n—>—
experimental
failure load—. _,
* * * *
LU
£ 300
o
2
o
200^
100
0
-5
o-o
experimental
- - calculated
j I i
5 10 15 20-5
[mm]
O—O experimental -
— calculated
J i l i
5 10 15 20 25 30
[mml
Fig. 5.3-12: Experimental and calculated midspan deflections
of the OA-2 and the A-2 beam.
around 30% of the failure load. With this in mind the agreement
is quite close except that the finite element models seem to be
a little too soft. This may be a consequence of the neglected
tension-stiffening effect as discussed in section 5.1. The predicted
failure load for the OA-2 beam is only 2% below the actual
one whereas the predicted failure load for the A-2 beam
underestimates the actual one by 20%. Thus the behaviour of the
beam without stirrups was predicted very closely. However,
existence of stirrups resulted experimentally in a 36% increase
of the failure load whereas the calculations estimate a 12% increase,
only. We will return to this aspect later on.
A sequence of calculations was performed to investigate the influence
of different parameters on the structural behaviour of
the beams. The influence of aggregate interlock as expressed by
the shear retention factor n, cf. section 4.2.2, dowel action
as modelled by the factor K, cf. section 4.3, the ratio of uniaxial
tensile to compressive strength, o./a , as well as the influence
of consideration to secondary cracks were investigated.
The results are given in table 2. In this table the term F ,_ /
theo.'
F exp. gives the ra tio of the theoretical failure load to the experimental
one. The ratio a /a is in accordance with table 1
except for case no. 4. Recall that the standard version of the