THE STRUCTURAL BEHAVIOUR AND ULTIMATE STRENGTH OF REINFORCED CONCRETE SLABS SRENGTHENED BY EPOXY-BONDED STEEL PLATES
THE STRUCTURAL BEHAVIOUR AND ULTIMATE STRENGTH OF REINFORCED CONCRETE SLABS SRENGTHENED BY EPOXY-BONDED STEEL PLATES
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Date
1998-10
Authors
Zubairu, Ibrahimu Khalilullahi
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Abstract
The structural behaviour and ultimate strength of concrete
slabs strengthened by epoxy-bonded steel plates was studied
by both analytical and experimental investigations. The
purpose was to evaluate their structural response at the
serviceability and ultimate limit states. Simple analytical
models that predict the ultimate behaviour of reinforced
concrete slabs with epoxy-bonded steel plates on the
tension face in the elastic and plastic regions were
developed. The analytical models were evaluated by
comparing analytical results with the test data for 13
slabs.
Thirteen concrete slabs were tested to failure under
central point load. The measured load versus deflection at
midspan of the slabs and the load versus strain in steel
plate were plotted and compared with the control slabs.
The ratio of the ultimate load of plated slabs to unplated
slabs was 4.78 and 1.92, for tension reinforcement ratio
0.00 and 0.71 respectively. The presence of glue alone
enabled the slabs to carry higher ultimate loads by up to
45 percent. These results clearly indicated the beneficial
effect of bonded plates in enhancing the ultimate flexural
strength of reinforced concrete slabs.
The glued plates also reduce the deflection and steel plate
strain at different rates and that the rate of reduction
varies with the applied load level. However, the stiffening
effect of the glued plates is much greater in controlling
cracking than in controlling deflection. Comparisons of the
analytical results with the test data obtained for
thirteen concrete slabs were also carried out. The
average ratio of experimental to theoretical ultimate
moment of both plated and unplated slabs was of the order
of 1.00, with a minimum of 0.64 and a maximum of 1.15.
Generally, a reasonably close agreement between the
calculated and measured data was noted.
The applicability of the plate bonding technique to
strengthen structurally damaged reinforced concrete slabs
was also examined. The structural behaviour of precracked
slabs, loaded up to 45 percent of their flexural capacity,
were reported. The results showed that strengthening, by
epoxy-bonded steel plates, of cracked slabs is structurally
efficient and that these plated slabs can carry higher
ultimate load from 72 to 98 percent of the original
unplated slabs. The restraining effect of the steel plates
on the existing cracks was, however, more pronounced when
the load was increased beyond the original preloading
value.
To explore the effectiveness of the epoxy give in
preserving composite action, slippage at the interface was
measured. The results revealed that provided epoxy with a
wide range of strengths and ductilities are used and
adequate precautions are observed in the gluing technique,
both slab action and full composite behaviour can be
maintained until failure. Slip measurements for the set of
test slabs varied from 0.018 to 1.930 mm.
Description
A Dissertations Submitted to the Postgraduate School, Ahmadu
Bello University, in partial fulfillment of the
requirements for the award of Doctor of Philosophy Degree
in Structural Engineering in the Department of Civil
Engineering, Faculty of Engineering, Ahmadu Bello
University, Zaria, Nigeria
October, 1998
Keywords
BEHAVIOUR,, STRUCTURAL,, ULTIMATE,, REINFORCED,, SLABS SRENGTHENED,, EPOXY-BONDED,, STEEL PLATES