Nonlinear Finite Element Analysis of Concrete Structures

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1. INTRODUCTION
The present report is devoted to nonlinear finite element analysis
of axisymmetric and plane concrete structures loaded in
the short-term up until failure. Additional to the prerequisites
for such analysis, namely constitutive modelling and finite element
techniques, emphasis is placed on the applications, where
real structures are analysed. It turns out that the finite element
analysis offers unique opportunities to investigate and
describe in physical terms the structural behaviour of concrete
structures.
The finite element analysis is performed using the program
AXIPLANE, developed at Risø. The use of this program is given
by the writer (1980). The scope of the present report is twofold:
(1) to provide an exposition of matters of general interest;
this relates to the constitutive modelling of concrete, to the
analysis of the considered structures and to some aspects of the
finite element modelling; (2) to give the specific theoretical
documentation of the AXIPLANE-program. Moreover, a selfcontained
exposition is aimed at.
The important section 2 treats constitutive modelling of concrete.
Both the strength and the stiffness of concrete under
various loadings are discussed and a constitutive model valid for
general triaxial stress states and previously proposed by the
writer is described and compared with experimental data.
Section 3 deals with the constitutive equations of reinforcement
and prestressing. These models are quite trivial and interest
is focussed only on a formulation that is computationally convenient
in the AXIPLANE-program.
Section 4 describes different finite elements aspects. The AXI­
PLANE-program uses triangular elements for simulation of the
concrete, whereas one- and two-dimensional elements simulate