Analysis of seismic behavior and influencing factors of reinforced UHPC columns

Abstract:

To study the seismic behavior and influencing factors of reinforced ultra-high performance concrete (UHPC) columns, by taking carbon fiber reinforced polymer (CFRP) sheet winding, steel strength, and shear span ratio as variables, tests were carried out on an ordinary steel reinforced UHPC column, an ordinary steel reinforced UHPC column wound with CFRP sheet, and three high-strength steel reinforced UHPC columns under low frequency cyclic loads. The failure mode, load-displacement curves, ductility, and energy dissipation capacity of the specimens were analyzed. Results show that the ductility and energy dissipation capacity of the reinforced UHPC columns with shear span ratio of 1.5-4.0 were good. Under CFRP sheet winding or large shear span ratio, the failure mode of the specimens changed from shear compression failure to bending shear failure, and the ductility was significantly improved. The bearing capacity and ductility of the specimens were improved by increasing the strength of the longitudinal steel and stirrups of the UHPC columns. The working capacity of the ordinary stirrups was poor after cracking, so it is suggested that the shear members of UHPC should be reinforced with stirrups with yield strength above 600 MPa. Based on the truss-arch model, the calculation formula of shear capacity of reinforced UHPC columns was established by taking account of the tensile contribution of steel fibers and the influences of axial compression ratio and shear span ratio. The calculated values agreed well with the test results, which can provide reference for the design of UHPC structures.