Tension stiffening effect in GFRP reinforced concrete elements

The deflection of Glass Fibre Reinforced Polymer Reinforced Concrete (GFRP RC) is
often
the governing criterion
for design. The lack of
fundamental
research particularly
on the tension stiffening behaviour of GFRP RC has hindered both the development of
fundamental equations
to predict deflection and the use of nonlinear Finite Element
(FE) analysis
for predicting the structural behaviour of GFRP RC. This thesis
investigates the tension stiffening effect of GFRP RC in an effort to improve the
predictability of GFRP RC deformation behaviour. The study adopts a holistic
approach
for tension stiffening which considers the bond as the building block for
tension stiffening modelling and
tension stiffening as being a macroscopic
representation of bond modelling.
In this study
tension stiffening
is experimentally evaluated
first against more generic
variables
like
concrete strength, reinforcement ratio and bar diameter. This is followed
by a detailed
study on bond between
concrete and GFRP which results
in
the
development of a strain distribution function to represent
bond between
cracks. This
formed the basis for the development of a comprehensive model
to analyse the tension
stiffening behaviour of direct tension tests. After evaluating
the tension stiffening
test
results against existing code-based
formulations, the CEB-FIP model
is
recalibrated
to
represent
the tension stiffening behaviour of GFRP RC, thereby providing a simplified
means
to evaluate
tension stiffening behaviour of GFRP RC.
The successful
implementation
of
the tension stiffening model
is demonstrated
through
the prediction of deflection of
flexural elements using a general nonlinear FE analysis
package
(ABAQUS) that uses the smeared crack approach
to model the reinforced
concrete behaviour.