Flexural performance of ECC-concrete composite beams strengthened with carbon fiber sheet

In order to study the strengthen effect of carbon fiber sheet (CFS) on steel reinforced engineering cemented composite (ECC)-concrete composite beams. Three groups with totally 12 specimens of steel reinforced ECCconcrete composite beams strengthened by CFS were made and their static flexural experiments were conducted. The effects of ECC replacement heights, layers of CFS pasted and CFS hoops on flexural behavior of ECCconcrete composite beams were investigated, in terms of strain, load bearing capacity, deflection, crack and failure pattern. The results show that compared with unstrengthened specimen, the crack width of CFS strengthened specimen was reduced and load bearing capacity was enhanced. The maximum improvement of load bearing capacity is 63%. Compared with strengthened specimen without CFS hoop, the load bearing capacity of strengthened specimen with CFS hoops improved 9%. Based on reasonable assumptions and materials simplified constitutive model, load bearing capacity of CFS strengthened concrete beam and ECC-concrete composite beam are developed. The values predicted by the formulas are in good agreement with the results tested, indicating the validity of formulae proposed and can be used in engineering practice.