Nonlinear Finite Element Analysis of Concrete Structures

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premature failure load. However, if no or insignificant cracking
occurs very large load increments can be utilized. In the examples
considered in the following section load increments around
2-4% of the ultimate load were employed.
The failure load is determined as the load in which a large number
of iterations is insufficient to satisfy both the constitutive
equations and the static equilibrium. This means that large
displacements occur corresponding to the maximum point on the
forec-displacement curve having a horizontal tangent. In the
present case 25 iterations are chosen as the limiting value.
It should be recalled that in the standard version of the prograr,
the shear retention factor n in cracked elements is r\ =
0.01. Moreover, no dowel action of the reinforcement is considered,
i.e., the value of K is < = 0.
5. EXAMPLES OF ANALYSIS OF CONCRETE STRUCTURES
While the previous sections have described in detail the theoretical
basis of the AXIPLANE-program, the present section will
treat examples of application of the program. In these examples,
all of which represent realistic structures difficult to investigate
by other theoretical means, a comparison with experimental
evidence will be carried out, so that the applicability of the
program can be evaluated. Moreover, apart from this obvious aspect
much effort will be placed on investigating the structural
behaviour of the analyzed concrete structures. In fact, the
AXIPLANE-program offers quite unique possibilities for gaining
insight in the load carrying mechanism of concrete structures
since not only is detailed information available throughout the
loading history, but different assumptions can easily be incorporated
enabling sensitivity studies to be carried out.
These two objectives: (1) evaluation of the applicability of the