Abstract:
The analysis of the observed behaviour and the structural
safety control of concrete dams under swelling processes,
namely due to alkali-silica reactions (ASR), require the use of
appropriate mathematical models, generally supported by the
finite element method. These models must take into account
the factors that influence the development of swelling
processes, namely the concrete properties, the environmental
conditions (temperature and humidity) and the stress field in
the structure, as well as the over-time changes in the
rheologic properties of materials and the damage induced by
swelling.
This purpose was achieved by a damage-chemo-viscoelastic
model, based on a constitutive isotropic damage law, which
consider that the evolution of the damage variables (both
tensile and compressive) depends exclusively on elastic
strains. The concrete time behaviour was taken into account
by an incremental constitutive relation corresponding to a
Kelvin chain. The hypothesis of isotropic material with a
time variable elasticity modulus and a constant Poisson ratio
was admitted. The free-stress swelling process is assumed to
be isotropic and the influence of the stress field was also
considered. This model makes it possible to compute
displacements, strains, stresses and damage over time.
This paper is to present the main features of the mathematical
models developed and the results of its application to the
analysis of the observed behaviour of an approximately 60-
years old Portuguese buttress dam, the Pracana dam, which
has been subject to a concrete swelling process due to ASR.
