含粗骨料超高性能混凝土单轴受压疲劳性能

Fatigue Performance of Ultra‑high Performance Concrete Containing Coarse Aggregate under Uniaxial Cyclic Compression

对含粗骨料超高性能混凝土(UHPC(CA))进行单轴受压疲劳试验,重点考察其疲劳破坏形态、疲劳变形、疲劳寿命及疲劳强度.在此基础上,分析了UHPC(CA)疲劳破坏全过程,建立了基于Weibull分布的存活率-应力水平-疲劳寿命(p‑S‑N)方程.结果表明:UHPC(CA)疲劳破坏形态为剪切破坏,破坏时试件呈现1条或2条主裂缝;UHPC(CA)疲劳破坏断面分为疲劳区和裂纹扩展区,疲劳区有明显的反复摩擦痕迹;UHPC(CA)疲劳变形发展呈现明显的三阶段特征,即微裂纹萌生发展阶段、微裂纹稳定发展和宏观裂缝萌生阶段、宏观裂缝发展阶段;UHPC(CA)单调应力-应变曲线仅在高应力水平(S≥0.8)下可作为其疲劳变形的包络线;UHPC(CA)具有95%存活率的疲劳强度为61.78 MPa,对应的应力水平为0.520.

The fatigue performance of ultra‑high performance concrete containing coarse aggregate(UHPC(CA))was investigated through the uniaxial compressive fatigue test.The fatigue failure pattern,fatigue deformation,fatigue life and fatigue strength of UHPC(CA)were studied.On this basis,the whole failure process of UHPC(CA)under fatigue load was analyzed,and the survival rate‑stress level‑fatigue life(p‑S‑N)equation was established based on the Weibull distribution.Results show that the fatigue failure pattern of UHPC(CA)is the shear failure with one or two main cracks.The fatigue failure surface of UHPC(CA)is composed of two zones,fatigue zone with obvious traces of repeated friction and crack propagation zone.Three stages are observed in the fatigue strain evolution curve,namely,micro‑crack initiation and development stage,micro‑crack stable development and macro‑crack initiation stage,and macro‑crack development stage.The monotonic stress‑strain curve of UHPC(CA)can be used as an envelope of fatigue deformation only at high stress levels(S≥0.8).The fatigue strength of UHPC(CA)with 95%survival rate can be taken as 61.78 MPa,and the corresponding stress level is 0.520.