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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 77
PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON CIVIL AND STRUCTURAL ENGINEERING COMPUTING Edited by: B.H.V. Topping
Paper 51
Evaluation of the Fiber Orientation Effects on the Ductility of the Confined Concrete Elements L. Anania, A. Badalà and G. Failla
Departement of Civil and Enviromental Engineering, Faculty of Engineering, University of Catania, Italy Full Bibliographic Reference for this paper
, "Evaluation of the Fiber Orientation Effects on the Ductility of the Confined Concrete Elements", in B.H.V. Topping, (Editor), "Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 51, 2003. doi:10.4203/ccp.77.51
Keywords: CFRP, rehabilitation, composite materials, wrapping concrete members.
Summary
Recent tests carried out on the benefit due to the use of the innovative materials
applied as confinement on the compressed elements (Carbon fibers, glass or kevlar),
encouraged the development of the wrapping technique for the reinforcement and
the retrofitting of important structures located in high seismic risk zone. Recently,
the composite materials have been employed for the confinement of concrete
elements in order to improve their mechanical features such as ductility and
resistance even when the elements are damaged, as in the case of seismc events. The
study reports the comparison between results obtained from an experimental
analysis carried out on a series of concrete cylindric samples confined by C-FRP.
Two series of specimens, each constituted by three groups differing for dimensions,
were prepared in order to evaluate the influence of the sand used; as well as of the
fibers orientation. Samples belonging to series G were characterized by a ratio
between Height and Diameter equal to 2:1; Samples belonging to series H were
characterized by a ratio between Height and Diameter equal to 3:1. Besides,
different orientation of the Carbon fiber layers were tested, namely (90o 45o 60o)
In the paper the experimental data was compared to the theoretical model reported in
literature [1] for the compressed element reinforced by the wrapping technique and
to a LUSAS F.E.M. analysis [2]. The gain in terms of resistance as well as of
ductility was determined by a function of different orientation, in respect to the axis
sample, of the applied CFRP layers The ultimate longitudinal strains, as well as the
transversal ones are much greater in respect to the unconfined sample, thus, the
strain energy increases with the ductility of the specimen. The load- displacement
behavior of the confinement specimens is described by a bilinear trend curve except
from the confined sample with fibers oriented at a
Generally, the unconfined samples tested show a first linear trend where a decrease
of volume is recorded due to the propagation of the micro-fractures [1], after that
two possible behaviours have been observed: unstable collapse in the positive strain
domain when the sample fails due to a increase of unstable compressibility; an
increment of volume and thus a trend inversion due to the propagation of the micro
fractures propagated. From the comparison between the series of the tested samples,
it can be noted that the curves regarding the H series samples are in the domain of
positive volumetric in respect to the ones of the G series; anyway each sample group
shows a very similar trend even when the fibres angle changes. The data obtained
shows that the real behavior of the confined columns with CFRP are influenced by
several parameters as: concrete quality, shape ratio between the height (H) and the
diameter (D), fiber thickness etc. this results in changes in failure mode, the ultimate
stress, the stiffness and the ductility. The confined samples show an increase of the
ultimate stress in respect to the unconfined case. This increment is greater when the
fiber inclination is close to 90o while the ultimate strains are always higher, as well
as the strain energy, this produces an increment of the sample ductility. For fibres
oriented at 90o in respect to the longitudinal axes of the sample the resistance is
three times greater than the unconfined sample while the fibers oriented at
References
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