The nonlinear viscoelastic behavior of reinforced concrete beams under sustained
loading is investigated in this paper. A theoretical model is developed, which is based
on the viscoelastic modified principle of superposition, and accounts for cracking,
nonlinear behavior in compression, shrinkage, aging, and the creep rupture
phenomenon of concrete. A nonlinear form of the relaxation modulus is presented,
which is introduced into the constitutive relations and the corresponding nonlinear
rheological Maxwell model, to account for damage. The governing equations are
solved through time-stepping numerical integration, which yields an exponential
algorithm following the expansion of the relaxation modulus into a Dirichlet series.
The determination of the section-equivalent rigidities and creep strains along the
cracked and uncracked regions is achieved through an iterative procedure at each
time step. The capabilities of the model are demonstrated through numerical
examples and parametric studies including comparison with test results
available in the literature. The results show that creep has various and different
influences on the structural response, and in some cases it may lead to a
reduction of the load-carrying capacity of the member by creep rupture-type of
failures.
Centre for Infrastructure
Engineering and Safety
The School of Civil and Environmental Engineering
The University of New South Wales
Sydney, NSW 2052
Australia
