Structural Performance of Rectangular Reinforced Concrete Shear Walls Retrofitted By Carbon Fiber Sheets

Abstract eng:
Many medium-rise and high-rise reinforced concrete buildings were damaged during the 2010 Maule Chile earthquake. For rectangular reinforced concrete walls that are without boundary column in some buildings, flexural compression failures of multistory shear walls drew a lot of attention. It was found that design of boundary end of structural walls and evaluation of deformation performance of the structural wall was important. On the other hand, it is thought that structural walls of existing buildings which is expected to be flexural compressive failure is preferred to be retrofitted for damage mitigation. In this study, a performance verification test is conducted on the use of carbon fiber sheets as a retrofitting method for rectangular reinforced concrete shear walls. Note that there have already been several reports published on the effectiveness of carbon fiber sheets retrofitting on walls failing in shear or on walls with a boundary column on one side. The focus is on the retrofitting walls that fail in flexural mode. In other words, although an increase in strength cannot be expected, carbon fiber sheets retrofitting can delay the concrete crushing of the wall base that occurs during flexural failure; and the aim is to verify this improvement in deformation performance due to carbon fiber sheets retrofitting. Three structural wall specimens were prepared in the test. The test variables selected were the presence/absence of carbon fiber sheets retrofitting and the extent of retrofitting. A specimen represents the non-retrofitted test specimen for understanding the basic behavior of the walls. Another specimen was retrofitted over the entire wall span while other specimen was partially retrofitted at the boundary ends of the wall. Specimens were loaded a cyclic horizontal lateral force under a constant axial load. And an additional moment was applied at the top of the specimen by controlling two vertical jacks to correspond to the acting shear force, such that the shear span ratio was 1.5. From the test, by retrofitting the rectangular reinforced concrete wall with carbon fiber sheets, it was found that postmaximum strength deterioration was more gradual, and deformation performance was improved. And ultimate deformation of specimen which was partially retrofitted at the boundary ends of the wall was larger than that of specimen which was retrofitted over the entire wall span. Strain of concrete of wall base in compression of retrofitted specimen was larger than that of non-retrofitted specimen at the ultimate deformation. Thus, it was expected that concrete of wall retrofitted by carbon fiber sheets would be resistant to lager compressive force than that of non-retrofitted wall in even large strain region. In addition, evaluation of ultimate flexural deformation of specimens was considered based on test results. It was found that calculated ultimate flexural deformation could be good agreement with test results in case of use of plastic hinge lengths of 200mm,which is 2.5 times as long as thickness of wall.

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