This research aims to investigate the behaviour of glass fibre reinforced
polymer bars (GFRP) reinforced continuous concrete deep beams. For this
purpose, experimental, analytical and numerical studies were conducted.
Nine continuous concrete deep beams reinforced with GFRP bars and one
specimen reinforced with steel bars were experimentally tested to failure. The
investigated parameters included shear span-to-overall depth ratio (𝑎/ℎ), size
effect and web reinforcement ratio. Two 𝑎/ℎ ratios of 1.0 and 1.7 and three
section heights of 300 mm, 600 mm and 800 mm as well as two web
reinforcement ratios of 0% and 0.4% were used. The longitudinal
reinforcement, compressive strength and beam width were kept constant at
1.2%, ≈55 MPa and 175 mm, respectively. The web reinforcement ratio
achieved the minimum requirements of the CSA S806-12. The experimental
results highlighted that the web reinforcement ratio improved the load
capacities by about 10% and 18% for specimens having 𝑎/ℎ ratios of 1.0 and
1.7, respectively. For specimens with web reinforcement, the increase of 𝑎/ℎ
ratio from 1.0 to 1.7 led to reductions in the load carrying capacity by about
33% and 29% for beams with overall depths of 300 mm and 600 mm,
respectively. Additionally, a considerable reduction occurred in the shear
strength due to the increase of the section depth from 300 mm to 600 mm. The
experimental results confirmed the impacts of web reinforcement and size
effect that were not considered by the strut-and-tie method (STM) of the only
code provision, the Canadian S806-12, that addressed such elements.
In this study, the STM was illustrated and simplified to be adopted for GFRP
RC continuous deep beams, and then, the experimental results obtained from
this study were employed to assess the performance of the effectiveness
factors suggested by the STMs of the American (ACI 318-2014), European
(EC2-04) and Canadian (S806-12) codes as well as those factors
recommended by the previous studies to predict the load capacities. It was
found that these methods were unable to reflect the influences of member size
and/or web reinforcement reasonably, the impact of which has been confirmed
by the current experimental investigation. Therefore, a new effectiveness
factor was recommended to be used with the STM. Additionally, an upper bound analysis was developed to predict the load capacities of the tested specimens considering a reduced bond strength of GFRP bars after assessing
the old version recommended for steel RC continuous deep beams. A good
agreement between the predicted results and the measured ones was
obtained with the mean and coefficient of variation values for
experimental/calculated results of 1.02 and 5.9%, respectively, for the STM
and 1.03 and 8.6%, respectively, for the upper-bound analysis.
A 2D finite element analysis using ABAQUS/Explicit approach was carried out
to introduce a model able to estimate the response of GFRP RC continuous
deep beams. Based on the experimental results extracted from the pullout
tests, the interface between the longitudinal reinforcement and concrete
surface was modelled using a cohesive element (COH2D4) tool available in
ABAQUS. Furthermore, a perfect bond between the longitudinal reinforcement
and surrounding concrete was also modelled to evaluate the validity of this
assumption introduced by many previous FE studies. To achieve a reasonable
agreement with the test results, a sensitivity analysis was implemented to
select the proper mesh size and concrete model variables. The suitability and
capability of the developed FE model were demonstrated by comparing its
predictions with the test results of beams tested experimentally. Model
validation showed a reasonable agreement with the experiments in terms of
the failure mode, total failure load and the load-deflection responses. The
perfect bond model has overestimated the predicted results in terms of
stiffness behaviour and failure load, while the cohesive element model was
more suitable to reflect the behaviour of those specimens. The validated FE
model was then employed to implement a parametric study for the key
parameters that govern the behaviour of beams tested and to achieve an in depth understanding of such elements. The parametric study showed that the
higher the 𝑎/ℎ ratio the more pronounced the effect of web and the longitudinal
reinforcements and the lower the effect of concrete compressive strength; and
vice versa when 𝑎/ℎ ratio reduces.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/18381 |
| Date | January 2019 |
| Creators | Shalookh, Othman H. Zinkaah |
| Contributors | Ashour, Ashraf, Sheehan, Therese |
| Publisher | University of Bradford, Faculty of Engineering and Informatics |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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