[Thesis]. Manchester, UK: The University of Manchester; 2018.
Using Fibre Reinforcing Polymer (FRP) composites for strengthening and rehabilitation
of reinforced concrete structures has been a viable technique for more than two decades.
Strengthening by FRP composites is often preferred to other strengthening techniques
like steel plates due to the formerĂ˘s special features, for example, it is lightweight,
non-corrosive, easy to install, has high tensile strength, and its use results in
only minimal changes to the external appearance of the structure. Additionally, the
labour costs are lower when using this material. The main objectives of this study
are: (1) to investigate the punching shear behaviour of slabs at corner column connections
strengthened by externally bonded FRP sheets using both modelling and experimental
methods. The study concentrates mainly on slabs without shear reinforcement that fail
initially due to punching shear; this is in order to enhance their serviceability
and ultimate loading capacity; (2) to investigate slabs at corner column connections
with openings; and (3) to increase understanding of the behaviour of such slabs and
provide recommendations for strengthening.
None of the current standardsĂ˘ specifications - like the ACI-440, Concrete Society
Technical Report TR55 and the Japanese Society of Civil Engineers JSCE - give the
required information for the design of concrete slab-column connections to withstand
punching shear. Furthermore, all the previous studies about the strengthening of slab-column
connections have dealt with interior columns; none have investigated the strengthening
of slabs at the corner column. Thus, this study is the first to investigate, both
experimentally and numerically, the effectiveness of strengthening slabs at the corner
column connection by using carbon fibre reinforcing polymer (CFRP) sheets.
The experimental programme comprises casting and testing four full-scale slabs that
have been designed and fabricated in order to simulate exterior slab-column connections.
One of them is the control specimen, which has been designed without any opening or
strengthening. One is similar to the control specimen but strengthened by CFRP sheets
around the corners. The last two slabs are designed similar to the control specimen
but they have openings close to the column. In addition to the openings, they are
strengthened by CFRP sheets.
In addition to the experimental programme, three-dimensional nonlinear finite element
models have been developed and validated against the experimental results. The comparison
between the experimental and the numerical results is based on deflections, ultimate
punching shear capacity, total strains of steel and CFRP reinforcements, crack pattern
and the failure mode. Results are also compared to the Eurocode 2, ACI and the JSCE
to predict the punching shear strength. It is concluded that bonding CFRP sheets to
strengthen a slab at the corner column can increase both the serviceability and the
ultimate strength by (11-21) % depending on the slab size. This limited increase is
associated with the small thickness of the CFRP sheets used in the study, which means
that there is only a small CFRP area resisting the tensile stresses; CFRP with a small
width is used due to the practical constraints.