Shear strengthening of pre-cracked and non pre cracked reinforced concrete continuous beams using bi directional CFRP strips
Shear failure of a reinforced concrete beam is catastrophic where it occurs suddenly and without any warning. The use of FRP sheet as a strengthening and repairing material is an effective method to enhance the shear capacity of the beam. Extensive researches have been conducted on the shear s...
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| Format: | Thesis |
| Language: | English English English |
| Published: |
2014
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/1216/1/24p%20NOORWIRDAWATI%20ALI.pdf http://eprints.uthm.edu.my/1216/2/NOORWIRDAWATI%20ALI%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/1216/3/NOORWIRDAWATI%20ALI%20WATERMARK.pdf |
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| Summary: | Shear failure of a reinforced concrete beam is catastrophic where it occurs suddenly
and without any warning. The use of FRP sheet as a strengthening and repairing
material is an effective method to enhance the shear capacity of the beam. Extensive
researches have been conducted on the shear strengthening of reinforced concrete
simply supported beams using FRP composites. However, strengthening continuous
beams in shear have received very little attention among the researchers although
most of the existing structures are in the form of continuous condition. Furthermore,
there are restraints to add shear reinforcement to the existing reinforced concrete
beams when beams are part of the floor-beam system. In the design guideline by
ACI 440 Committee mentioned that the existing theoretical model have not been
confirmed to be use for strengthening in negative moment region which existed in
continuous beam. Therefore, in order to address the problem, a study on shear
strengthening of reinforced concrete continuous beam using CFRP strips was
conducted. An experimental work on 14 full-scale reinforced concrete continuous
beams with a size of 150x350x5800mm was carried out. Simulation using finite
element software ATENA v4 and theoretical analysis was also conducted. The
variables involved a number of CFRP strips layers (one and two layers), wrapping
schemes (four sides and three sides), orientation of CFRP strips (0/90 and 45/135
degree) and shear span to effective depth ratio, av/d (2.5 and 3.5). The type of FRP
used was bi-directional CFRP strips. Two beams were un-strengthened and treated
as the control specimens whilst the other 12 beam were wrapped with CFRP strips.
From the experimental results, all beams failed in shear as expected. Beams wrapped
with CFRP strips recorded shear capacity enhancement of around 10.12% to 53.74%
compared to the control specimens. Beam wrapped with two layers of CFRP strips at
four sides of the beam recorded the highest shear enhancement. Simulation study
also showed similar behaviour in terms of shear capacity and crack patterns. Three
existing theoretical models; ACI 440, Khalifa and Nanni and fib models were
adopted for theoretical comparison of shear capacity contributed by CFRP, Vf while
for shear capacity contributed by concrete, Vc and stirrups, Vs, the equation from
ACI 318-08, BS8110 and EC2 was adopted. The ACI 440 model had shown the
closer value with the experimental results and a modified ACI 440 model was
proposed on the effective strain limit and bond-reduction coefficient. |
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