配筋UHPC柱的抗震性能及影响因素分析

Analysis of seismic behavior and influencing factors of reinforced UHPC columns

摘要:

为研究配筋超高性能混凝土(ultra-high performance concrete, UHPC)柱抗震性能及影响因素,以碳纤维增强树脂(carbon fiber reinforced polymer, CFRP)布缠绕、钢筋强度和剪跨比为参变量,对1根普通钢筋UHPC柱、1根CFRP布缠绕的普通钢筋UHPC柱和3根高强钢筋UHPC柱进行了低周往复试验,分析了试件的破坏形态、荷载-位移曲线、延性和耗能能力等。结果表明:对于剪跨比为1.5~4.0的配筋UHPC柱,延性及耗能能力均较好；在CFRP缠绕或较大剪跨比下,试件的破坏形态由剪压破坏转变为弯剪破坏,延性得到明显改善；提高UHPC柱纵筋和箍筋的强度可提高试件的承载力和延性；普通箍筋的裂后工作能力较差,建议UHPC受剪构件配置屈服强度在600 MPa以上的箍筋；基于桁架-拱模型,建立了考虑钢纤维抗拉贡献、轴压比和剪跨比影响的配筋UHPC柱的抗剪承载力计算公式,计算值与试验值吻合较好,可为UHPC结构设计提供参考。

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.