| 1. |
- Enochsson, Ola, et al.
(author)
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CFRP strengthened openings in two-way concrete slabs : an experimental and numerical study
- 2007
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In: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 21:4, s. 810-826
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Journal article (peer-reviewed)abstract
- Rehabilitation and strengthening of concrete structures with externally bonded fibre reinforced polymers (FRPs) has been a viable technique for at least a decade. An interesting and useful application is strengthening of slabs or walls where openings are introduced. In these situations, FRP sheets are very suitable; not only because of their strength, but also due to that they are easy to apply in comparison to traditional steel girders or other lintel systems. Even though many benefits have been shown by strengthening openings with FRPs not much research have been presented in the literature. In this paper, laboratory tests on 11 slabs with openings, loaded with a distributed load are presented together with analytical and numerical evaluations. Six slabs with openings have been strengthened with carbon fibre reinforced polymers (CFRPs) sheets. These slabs are compared with traditionally steel reinforced slabs, both with (four slabs) and without openings (one slab). The slabs are quadratic with a side length of 2.6 m and a thickness of 100 mm. Two different sizes of openings are used, 0.85 × 0.85 m and 1.2 × 1.2 m. The results from the tests show that slabs with openings can be strengthened with externally bonded CFRP sheets. The performance is even better than for traditionally steel reinforced slabs. The numerical and analytical evaluations show good agreement with the experimental results.
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| 2. |
- Rusinowski, Piotr, et al.
(author)
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Intermediate crack induced debonding in concrete beams strengthened with CFRP plates
- 2009
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In: Advances in Structural Engineering. - : SAGE Publications. - 1369-4332 .- 2048-4011. ; 12:6, s. 793-806
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Journal article (peer-reviewed)abstract
- FRP composites are becoming a material of choice in an increasing number of rehabilitation and retrofitting projects around the world. Depending on the design objectives, these materials can be used to improve one or more of the structural member characteristics, such as the load capacity, ductility and even durability. Design of structural strengthening applications using externally bonded FRP composites is usually based on conventional design approaches with improvement to account for the presence and characteristics of the FRP material. Non-conventional design issues that are specific to the type of application require special considerations for their proper inclusion in the design process. One such design issue is the debonding problems in externally bonded FRP strengthening applications that have been a concern and a research challenge since the initial development stages of the strengthening method. End-peeling has governed a large interest and several debonding models have been presented. However, interfacial peeling at flexural cracks has not attained the same focus - even though this debonding failure is most likely more common. This paper presents laboratory tests of concrete beams strengthened in flexure with CFRP epoxy bonded plates. Wrapping with CFRP sheets was applied in order to try to localize the failure initiation. Concrete cracking as well as debonding initiation and propagation was possible to observe with help of advanced optical measuring system and high speed camera.
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