Stress-Strain Relationship of Concrete Retrofitted With Carbon Fiber Sheet Under Cyclic Loading

Abstract eng:
Earthquakes are caused by a sudden release of energy from the movement between tectonic plates; besides geological faults and volcanism. As Peru is located in a high seismic hazard zone, it is necessary to improve the seismic response of buildings against earthquakes. In addition, in recent years, large scale construction of medium-rise building that use low ductility reinforced concrete wall (LDRC) has become commonplace in Peru. These walls do not have boundary columns but instead have a small quantity of reinforcing bars at each end and therefore expected to fail in flexural mode. To improve seismic response against earthquakes, two verification tests were conducted by using carbon fiber sheet (CFS) as a retrofitting method in Toyohashi University of Technology, Japan. The first test was conducted over three LDRC walls (Without CFS, full wall retrofitted with CFS and edges retrofitted with CFS). The second test was conducted following the same retrofitted pattern of the first experiment but with a partial height retrofitted with CFS. From those tests, it was verified that carbon fiber sheets delay the concrete crushing of the wall base that occurs during flexural failure and that deformation performance was improved. To verify the confinement effect of CFS, a third experiment was conducted using concrete samples with CFS by changing the size, shape and number of CFS layers. In total, 39 concrete samples (Circular shape: 8-φ150x300mm, Square shape: 9-150x150x300mm, 2-150x150x450mm, Rectangular shape: 4-150x300x300mm, 2-150x300x450mm, 5100x300x200mm, 2-100x300x300mm, 5-100x400x200mm, 2-100x400x300mm, ) were tested under compressive loading (monotonic and cyclic). From the experiment, it was confirmed that deformation performance was improved and the strength of the concrete was increased due to the confinement provided by the CFS, however the stress-strain relationship of concrete with CFS depends on the shape of the concrete sample. This study will focus on the third experiment corresponding to the circular and square shaped specimens. A model of stress-strain relationship of concrete with CFS was proposed and compared with the experimental results. Parameters which affect the stress-strain relationship were discussed, such as: sample shape, confinement ratio, etc.

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