Nonlinear Finite Element Analysis of Concrete Structures

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large failure capacity when a * 0. A further disadvantage of
using K-values larger than zero is that the lateral bar stiffness
then depends on the shear strain that may be a result not
only of displacements normal to the bar direction, but also of
displacements parallel to this direction. Based on the above and
on findings in section 5.3, the value K = 0, i.e., no lateral
bar stiffness, will therefore be employed universally in the program
except for certain sensitivity studies related to beams
failing in shear, cf. section 5.3. It can therefore be concluded
that consideration to lateral bar stiffness should be treated
through its bending stiffness. However, within the practical
limitations of the present program discussed in section 4.3 such
an approach is not applicable h^re.
On the other hind, the value K - 0 results in a considerable
overestimate of the horizontal displacements as shown in fig.
3. However, this is presumed to be of minor importance as the
panels are very special structures where only the bars contribute
to the very small lateral stiffness. In most other structures
such a situation will not arise as cracks usually do not
cross a whole section and sufficient restraint along the crack
plane is therefore easily established by the uncracked concrete.
As previously discussed in section 4.2.2 the shear retention
f-ctor n is assumed to be 1%. However, in fig. 3 the consequence
of using the smaller value n = 0.5% is also indicated and it
appears that very large overestimations then result for small
a-values. In fact, as demonstrated earlier by Cervenka and
Gerstle (1971), the value n = 0 gives rise to a discontinuity
for a = 0, as an infinitely small a-value results in infinitely
large horizontal displacements. Apart from the previous arguments
given in section 4.2.2 the aforementioned support the employed
n-value equal to 1%.
Por K = 0 the predictions for vertical displacements are compared
with experimental values in fig. 5 as a function of loading.
As mentioned previously the panels with a = 10° and 20°
include vertical reinforcement not included in the analysis.
Even so, the experimental values are remarkably smaller than the